private inheritance - Page 183

Looking for something to add some standard rules for my c++ project.

- by rkb

Hello all, My team is developing a C++ project on linux. We use vim as editor. I want to enforce some code standard rules in our team in such a way that if the code is not in accordance with it, some sort of warning or error will be thrown when it builds or compiles. Not necessarily it builds but at least I can run some plugin or tools on that code to make sure it meets the standard. So that before committing to svn everyone need to run the code through some sort of plugin or script and make sure it meets the requirement and then only he/she can commit. Not sure if we can add some rules to vim, if there are any let me know about it. For eg. In our code standards all the member variables and private functions should start with _ class A{ private: int _count; float _amount; void _increment_count(){ ++_count; } } So I want to throw some warning or error or some sort of messages for this class if the variables are declared as follows. class A{ private: int count; float amount; void increment_count(){ ++_count; } } Please note that warning and error are not from compiler becoz program is still valid. Its from the tool I want to use so that code goes to re-factoring but still works fine on the executable side. I am looking for some sort of plugin or pre parsers or scripts which will help me in achieving all this. Currently we use svn; just to anser the comment.

Read the article

VB Change Calulator

- by BlueBeast

I am creating a VB 2008 change calculator as an assignment. The program is to use the amount paid - the amount due to calculate the total.(this is working fine). After that, it is to break that amount down into dollars, quarters, dimes, nickels, and pennies. The problem I am having is that sometimes the quantity of pennies, nickels or dimes will be a negative number. For example $2.99 = 3 Dollars and -1 Pennies. SOLVED Thanks to the responses, here is what I was able to make work with my limited knowledge. Option Explicit On Option Strict Off Option Infer Off Public Class frmMain Private Sub btnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClear.Click 'Clear boxes lblDollarsAmount.Text = String.Empty lblQuartersAmount.Text = String.Empty lblDimesAmount.Text = String.Empty lblNickelsAmount.Text = String.Empty lblPenniesAmount.Text = String.Empty txtOwed.Text = String.Empty txtPaid.Text = String.Empty lblAmountDue.Text = String.Empty txtOwed.Focus() End Sub Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click 'Close application' Me.Close() End Sub Private Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click ' Find Difference between Total Price and Total Received lblAmountDue.Text = Val(txtPaid.Text) - Val(txtOwed.Text) Dim intChangeAmount As Integer = lblAmountDue.Text * 100 'Declare Integers Dim intDollarsBack As Integer Dim intQuartersBack As Integer Dim intDimesBack As Integer Dim intNickelsBack As Integer Dim intPenniesBack As Integer ' Change Values Const intDollarValue As Integer = 100 Const intQuarterValue As Integer = 25 Const intDimeValue As Integer = 10 Const intNickelValue As Integer = 5 Const intPennyValue As Integer = 1 'Dollars intDollarsBack = CInt(Val(intChangeAmount \ intDollarValue)) intChangeAmount = intChangeAmount - Val(Val(intDollarsBack) * intDollarValue) lblDollarsAmount.Text = intDollarsBack.ToString 'Quarters intQuartersBack = CInt(Val(intChangeAmount \ intQuarterValue)) intChangeAmount = intChangeAmount - Val(Val(intQuartersBack) * intQuarterValue) lblQuartersAmount.Text = intQuartersBack.ToString 'Dimes intDimesBack = CInt(Val(intChangeAmount \ intDimeValue)) intChangeAmount = intChangeAmount - Val(Val(intDimesBack) * intDimeValue) lblDimesAmount.Text = intDimesBack.ToString 'Nickels intNickelsBack = CInt(Val(intChangeAmount \ intNickelValue)) intChangeAmount = intChangeAmount - Val(Val(intNickelsBack) * intNickelValue) lblNickelsAmount.Text = intNickelsBack.ToString 'Pennies intPenniesBack = CInt(Val(intChangeAmount \ intPennyValue)) intChangeAmount = intChangeAmount - Val(Val(intPenniesBack) * intPennyValue) lblPenniesAmount.Text = intPenniesBack.ToString End Sub End Class

Read the article

Using addMouseListener() and paintComponent() for JPanel

- by Alex

This is a follow-up to my previous question. I've simplified things as much as I could, and it still doesn't work! Although the good thing I got around using getGraphics(). A detailed explanation on what goes wrong here is massively appreciated. My suspicion is that something's wrong with the the way I used addMouseListener() method here. import java.awt.Color; import java.awt.Graphics; import java.awt.event.MouseAdapter; import java.awt.event.MouseEvent; import javax.swing.JFrame; import javax.swing.JPanel; public class MainClass1{ private static PaintClass22 inst2 = new PaintClass22(); public static void main(String args[]){ JFrame frame1 = new JFrame(); frame1.add(inst2); frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame1.setTitle("NewPaintToolbox"); frame1.setSize(200, 200); frame1.setLocationRelativeTo(null); frame1.setVisible(true); } } class PaintClass11 extends MouseAdapter{ int xvar; int yvar; static PaintClass22 inst1 = new PaintClass22(); public PaintClass11(){ inst1.addMouseListener(this); inst1.addMouseMotionListener(this); } @Override public void mouseClicked(MouseEvent arg0) { // TODO Auto-generated method stub xvar = arg0.getX(); yvar = arg0.getY(); inst1.return_paint(xvar, yvar); } } class PaintClass22 extends JPanel{ private static int varx; private static int vary; public void return_paint(int input1, int input2){ varx = input1; vary = input2; repaint(varx,vary,10,10); } public void paintComponent(Graphics g){ super.paintComponents(g); g.setColor(Color.RED); g.fillRect(varx, vary, 10, 10); } }

Read the article

C++11 decltype requires instantiated object

- by snipes83

I was experimenting a little with the C++11 standard and came up with this problem: In C++11 you can use auto and decltype to automatically get return type for a function as, for example the begin() and end() functions below: #include <vector> template <typename T> class Container { private: std::vector<T> v; public: auto begin() -> decltype(v.begin()) { return v.begin(); }; auto end() -> decltype(v.end()) { return v.end(); }; }; My problem here is that I have to declare the private vector<T> v before the public declarations which is against my coding style. I would like to declare all my private members after my public members. You have to declare the vector before the function declaration because the expression in decltype is a call to vector member function begin() and requires an instance of the object. Is there a way around this?

Read the article

C#/.NET Little Wonders: The ConcurrentDictionary

- by James Michael Hare

Once again we consider some of the lesser known classes and keywords of C#. In this series of posts, we will discuss how the concurrent collections have been developed to help alleviate these multi-threading concerns. Last week’s post began with a general introduction and discussed the ConcurrentStack<T> and ConcurrentQueue<T>. Today's post discusses the ConcurrentDictionary<T> (originally I had intended to discuss ConcurrentBag this week as well, but ConcurrentDictionary had enough information to create a very full post on its own!). Finally next week, we shall close with a discussion of the ConcurrentBag<T> and BlockingCollection<T>. For more of the "Little Wonders" posts, see the index here. Recap As you'll recall from the previous post, the original collections were object-based containers that accomplished synchronization through a Synchronized member. While these were convenient because you didn't have to worry about writing your own synchronization logic, they were a bit too finely grained and if you needed to perform multiple operations under one lock, the automatic synchronization didn't buy much. With the advent of .NET 2.0, the original collections were succeeded by the generic collections which are fully type-safe, but eschew automatic synchronization. This cuts both ways in that you have a lot more control as a developer over when and how fine-grained you want to synchronize, but on the other hand if you just want simple synchronization it creates more work. With .NET 4.0, we get the best of both worlds in generic collections. A new breed of collections was born called the concurrent collections in the System.Collections.Concurrent namespace. These amazing collections are fine-tuned to have best overall performance for situations requiring concurrent access. They are not meant to replace the generic collections, but to simply be an alternative to creating your own locking mechanisms. Among those concurrent collections were the ConcurrentStack<T> and ConcurrentQueue<T> which provide classic LIFO and FIFO collections with a concurrent twist. As we saw, some of the traditional methods that required calls to be made in a certain order (like checking for not IsEmpty before calling Pop()) were replaced in favor of an umbrella operation that combined both under one lock (like TryPop()). Now, let's take a look at the next in our series of concurrent collections!For some excellent information on the performance of the concurrent collections and how they perform compared to a traditional brute-force locking strategy, see this wonderful whitepaper by the Microsoft Parallel Computing Platform team here. ConcurrentDictionary – the fully thread-safe dictionary The ConcurrentDictionary<TKey,TValue> is the thread-safe counterpart to the generic Dictionary<TKey, TValue> collection. Obviously, both are designed for quick – O(1) – lookups of data based on a key. If you think of algorithms where you need lightning fast lookups of data and don’t care whether the data is maintained in any particular ordering or not, the unsorted dictionaries are generally the best way to go. Note: as a side note, there are sorted implementations of IDictionary, namely SortedDictionary and SortedList which are stored as an ordered tree and a ordered list respectively. While these are not as fast as the non-sorted dictionaries – they are O(log2 n) – they are a great combination of both speed and ordering -- and still greatly outperform a linear search. Now, once again keep in mind that if all you need to do is load a collection once and then allow multi-threaded reading you do not need any locking. Examples of this tend to be situations where you load a lookup or translation table once at program start, then keep it in memory for read-only reference. In such cases locking is completely non-productive. However, most of the time when we need a concurrent dictionary we are interleaving both reads and updates. This is where the ConcurrentDictionary really shines! It achieves its thread-safety with no common lock to improve efficiency. It actually uses a series of locks to provide concurrent updates, and has lockless reads! This means that the ConcurrentDictionary gets even more efficient the higher the ratio of reads-to-writes you have. ConcurrentDictionary and Dictionary differences For the most part, the ConcurrentDictionary<TKey,TValue> behaves like it’s Dictionary<TKey,TValue> counterpart with a few differences. Some notable examples of which are: Add() does not exist in the concurrent dictionary. This means you must use TryAdd(), AddOrUpdate(), or GetOrAdd(). It also means that you can’t use a collection initializer with the concurrent dictionary. TryAdd() replaced Add() to attempt atomic, safe adds. Because Add() only succeeds if the item doesn’t already exist, we need an atomic operation to check if the item exists, and if not add it while still under an atomic lock. TryUpdate() was added to attempt atomic, safe updates. If we want to update an item, we must make sure it exists first and that the original value is what we expected it to be. If all these are true, we can update the item under one atomic step. TryRemove() was added to attempt atomic, safe removes. To safely attempt to remove a value we need to see if the key exists first, this checks for existence and removes under an atomic lock. AddOrUpdate() was added to attempt an thread-safe “upsert”. There are many times where you want to insert into a dictionary if the key doesn’t exist, or update the value if it does. This allows you to make a thread-safe add-or-update. GetOrAdd() was added to attempt an thread-safe query/insert. Sometimes, you want to query for whether an item exists in the cache, and if it doesn’t insert a starting value for it. This allows you to get the value if it exists and insert if not. Count, Keys, Values properties take a snapshot of the dictionary. Accessing these properties may interfere with add and update performance and should be used with caution. ToArray() returns a static snapshot of the dictionary. That is, the dictionary is locked, and then copied to an array as a O(n) operation. GetEnumerator() is thread-safe and efficient, but allows dirty reads. Because reads require no locking, you can safely iterate over the contents of the dictionary. The only downside is that, depending on timing, you may get dirty reads. Dirty reads during iteration The last point on GetEnumerator() bears some explanation. Picture a scenario in which you call GetEnumerator() (or iterate using a foreach, etc.) and then, during that iteration the dictionary gets updated. This may not sound like a big deal, but it can lead to inconsistent results if used incorrectly. The problem is that items you already iterated over that are updated a split second after don’t show the update, but items that you iterate over that were updated a split second before do show the update. Thus you may get a combination of items that are “stale” because you iterated before the update, and “fresh” because they were updated after GetEnumerator() but before the iteration reached them. Let’s illustrate with an example, let’s say you load up a concurrent dictionary like this: 1: // load up a dictionary. 2: var dictionary = new ConcurrentDictionary<string, int>(); 3: 4: dictionary["A"] = 1; 5: dictionary["B"] = 2; 6: dictionary["C"] = 3; 7: dictionary["D"] = 4; 8: dictionary["E"] = 5; 9: dictionary["F"] = 6; Then you have one task (using the wonderful TPL!) to iterate using dirty reads: 1: // attempt iteration in a separate thread 2: var iterationTask = new Task(() => 3: { 4: // iterates using a dirty read 5: foreach (var pair in dictionary) 6: { 7: Console.WriteLine(pair.Key + ":" + pair.Value); 8: } 9: }); And one task to attempt updates in a separate thread (probably): 1: // attempt updates in a separate thread 2: var updateTask = new Task(() => 3: { 4: // iterates, and updates the value by one 5: foreach (var pair in dictionary) 6: { 7: dictionary[pair.Key] = pair.Value + 1; 8: } 9: }); Now that we’ve done this, we can fire up both tasks and wait for them to complete: 1: // start both tasks 2: updateTask.Start(); 3: iterationTask.Start(); 4: 5: // wait for both to complete. 6: Task.WaitAll(updateTask, iterationTask); Now, if I you didn’t know about the dirty reads, you may have expected to see the iteration before the updates (such as A:1, B:2, C:3, D:4, E:5, F:6). However, because the reads are dirty, we will quite possibly get a combination of some updated, some original. My own run netted this result: 1: F:6 2: E:6 3: D:5 4: C:4 5: B:3 6: A:2 Note that, of course, iteration is not in order because ConcurrentDictionary, like Dictionary, is unordered. Also note that both E and F show the value 6. This is because the output task reached F before the update, but the updates for the rest of the items occurred before their output (probably because console output is very slow, comparatively). If we want to always guarantee that we will get a consistent snapshot to iterate over (that is, at the point we ask for it we see precisely what is in the dictionary and no subsequent updates during iteration), we should iterate over a call to ToArray() instead: 1: // attempt iteration in a separate thread 2: var iterationTask = new Task(() => 3: { 4: // iterates using a dirty read 5: foreach (var pair in dictionary.ToArray()) 6: { 7: Console.WriteLine(pair.Key + ":" + pair.Value); 8: } 9: }); The atomic Try…() methods As you can imagine TryAdd() and TryRemove() have few surprises. Both first check the existence of the item to determine if it can be added or removed based on whether or not the key currently exists in the dictionary: 1: // try add attempts an add and returns false if it already exists 2: if (dictionary.TryAdd("G", 7)) 3: Console.WriteLine("G did not exist, now inserted with 7"); 4: else 5: Console.WriteLine("G already existed, insert failed."); TryRemove() also has the virtue of returning the value portion of the removed entry matching the given key: 1: // attempt to remove the value, if it exists it is removed and the original is returned 2: int removedValue; 3: if (dictionary.TryRemove("C", out removedValue)) 4: Console.WriteLine("Removed C and its value was " + removedValue); 5: else 6: Console.WriteLine("C did not exist, remove failed."); Now TryUpdate() is an interesting creature. You might think from it’s name that TryUpdate() first checks for an item’s existence, and then updates if the item exists, otherwise it returns false. Well, note quite... It turns out when you call TryUpdate() on a concurrent dictionary, you pass it not only the new value you want it to have, but also the value you expected it to have before the update. If the item exists in the dictionary, and it has the value you expected, it will update it to the new value atomically and return true. If the item is not in the dictionary or does not have the value you expected, it is not modified and false is returned. 1: // attempt to update the value, if it exists and if it has the expected original value 2: if (dictionary.TryUpdate("G", 42, 7)) 3: Console.WriteLine("G existed and was 7, now it's 42."); 4: else 5: Console.WriteLine("G either didn't exist, or wasn't 7."); The composite Add methods The ConcurrentDictionary also has composite add methods that can be used to perform updates and gets, with an add if the item is not existing at the time of the update or get. The first of these, AddOrUpdate(), allows you to add a new item to the dictionary if it doesn’t exist, or update the existing item if it does. For example, let’s say you are creating a dictionary of counts of stock ticker symbols you’ve subscribed to from a market data feed: 1: public sealed class SubscriptionManager 2: { 3: private readonly ConcurrentDictionary<string, int> _subscriptions = new ConcurrentDictionary<string, int>(); 4: 5: // adds a new subscription, or increments the count of the existing one. 6: public void AddSubscription(string tickerKey) 7: { 8: // add a new subscription with count of 1, or update existing count by 1 if exists 9: var resultCount = _subscriptions.AddOrUpdate(tickerKey, 1, (symbol, count) => count + 1); 10: 11: // now check the result to see if we just incremented the count, or inserted first count 12: if (resultCount == 1) 13: { 14: // subscribe to symbol... 15: } 16: } 17: } Notice the update value factory Func delegate. If the key does not exist in the dictionary, the add value is used (in this case 1 representing the first subscription for this symbol), but if the key already exists, it passes the key and current value to the update delegate which computes the new value to be stored in the dictionary. The return result of this operation is the value used (in our case: 1 if added, existing value + 1 if updated). Likewise, the GetOrAdd() allows you to attempt to retrieve a value from the dictionary, and if the value does not currently exist in the dictionary it will insert a value. This can be handy in cases where perhaps you wish to cache data, and thus you would query the cache to see if the item exists, and if it doesn’t you would put the item into the cache for the first time: 1: public sealed class PriceCache 2: { 3: private readonly ConcurrentDictionary<string, double> _cache = new ConcurrentDictionary<string, double>(); 4: 5: // adds a new subscription, or increments the count of the existing one. 6: public double QueryPrice(string tickerKey) 7: { 8: // check for the price in the cache, if it doesn't exist it will call the delegate to create value. 9: return _cache.GetOrAdd(tickerKey, symbol => GetCurrentPrice(symbol)); 10: } 11: 12: private double GetCurrentPrice(string tickerKey) 13: { 14: // do code to calculate actual true price. 15: } 16: } There are other variations of these two methods which vary whether a value is provided or a factory delegate, but otherwise they work much the same. Oddities with the composite Add methods The AddOrUpdate() and GetOrAdd() methods are totally thread-safe, on this you may rely, but they are not atomic. It is important to note that the methods that use delegates execute those delegates outside of the lock. This was done intentionally so that a user delegate (of which the ConcurrentDictionary has no control of course) does not take too long and lock out other threads. This is not necessarily an issue, per se, but it is something you must consider in your design. The main thing to consider is that your delegate may get called to generate an item, but that item may not be the one returned! Consider this scenario: A calls GetOrAdd and sees that the key does not currently exist, so it calls the delegate. Now thread B also calls GetOrAdd and also sees that the key does not currently exist, and for whatever reason in this race condition it’s delegate completes first and it adds its new value to the dictionary. Now A is done and goes to get the lock, and now sees that the item now exists. In this case even though it called the delegate to create the item, it will pitch it because an item arrived between the time it attempted to create one and it attempted to add it. Let’s illustrate, assume this totally contrived example program which has a dictionary of char to int. And in this dictionary we want to store a char and it’s ordinal (that is, A = 1, B = 2, etc). So for our value generator, we will simply increment the previous value in a thread-safe way (perhaps using Interlocked): 1: public static class Program 2: { 3: private static int _nextNumber = 0; 4: 5: // the holder of the char to ordinal 6: private static ConcurrentDictionary<char, int> _dictionary 7: = new ConcurrentDictionary<char, int>(); 8: 9: // get the next id value 10: public static int NextId 11: { 12: get { return Interlocked.Increment(ref _nextNumber); } 13: } Then, we add a method that will perform our insert: 1: public static void Inserter() 2: { 3: for (int i = 0; i < 26; i++) 4: { 5: _dictionary.GetOrAdd((char)('A' + i), key => NextId); 6: } 7: } Finally, we run our test by starting two tasks to do this work and get the results… 1: public static void Main() 2: { 3: // 3 tasks attempting to get/insert 4: var tasks = new List<Task> 5: { 6: new Task(Inserter), 7: new Task(Inserter) 8: }; 9: 10: tasks.ForEach(t => t.Start()); 11: Task.WaitAll(tasks.ToArray()); 12: 13: foreach (var pair in _dictionary.OrderBy(p => p.Key)) 14: { 15: Console.WriteLine(pair.Key + ":" + pair.Value); 16: } 17: } If you run this with only one task, you get the expected A:1, B:2, ..., Z:26. But running this in parallel you will get something a bit more complex. My run netted these results: 1: A:1 2: B:3 3: C:4 4: D:5 5: E:6 6: F:7 7: G:8 8: H:9 9: I:10 10: J:11 11: K:12 12: L:13 13: M:14 14: N:15 15: O:16 16: P:17 17: Q:18 18: R:19 19: S:20 20: T:21 21: U:22 22: V:23 23: W:24 24: X:25 25: Y:26 26: Z:27 Notice that B is 3? This is most likely because both threads attempted to call GetOrAdd() at roughly the same time and both saw that B did not exist, thus they both called the generator and one thread got back 2 and the other got back 3. However, only one of those threads can get the lock at a time for the actual insert, and thus the one that generated the 3 won and the 3 was inserted and the 2 got discarded. This is why on these methods your factory delegates should be careful not to have any logic that would be unsafe if the value they generate will be pitched in favor of another item generated at roughly the same time. As such, it is probably a good idea to keep those generators as stateless as possible. Summary The ConcurrentDictionary is a very efficient and thread-safe version of the Dictionary generic collection. It has all the benefits of type-safety that it’s generic collection counterpart does, and in addition is extremely efficient especially when there are more reads than writes concurrently. Tweet Technorati Tags: C#, .NET, Concurrent Collections, Collections, Little Wonders, Black Rabbit Coder,James Michael Hare

Read the article

Using the ASP.NET Cache to cache data in a Model or Business Object layer, without a dependency on System.Web in the layer - Part One.

- by Rhames

ASP.NET applications can make use of the System.Web.Caching.Cache object to cache data and prevent repeated expensive calls to a database or other store. However, ideally an application should make use of caching at the point where data is retrieved from the database, which typically is inside a Business Objects or Model layer. One of the key features of using a UI pattern such as Model-View-Presenter (MVP) or Model-View-Controller (MVC) is that the Model and Presenter (or Controller) layers are developed without any knowledge of the UI layer. Introducing a dependency on System.Web into the Model layer would break this independence of the Model from the View. This article gives a solution to this problem, using dependency injection to inject the caching implementation into the Model layer at runtime. This allows caching to be used within the Model layer, without any knowledge of the actual caching mechanism that will be used. Create a sample application to use the caching solution Create a test SQL Server database This solution uses a SQL Server database with the same Sales data used in my previous post on calculating running totals. The advantage of using this data is that it gives nice slow queries that will exaggerate the effect of using caching! To create the data, first create a new SQL database called CacheSample. Next run the following script to create the Sale table and populate it: USE CacheSample GO CREATE TABLE Sale(DayCount smallint, Sales money) CREATE CLUSTERED INDEX ndx_DayCount ON Sale(DayCount) go INSERT Sale VALUES (1,120) INSERT Sale VALUES (2,60) INSERT Sale VALUES (3,125) INSERT Sale VALUES (4,40) DECLARE @DayCount smallint, @Sales money SET @DayCount = 5 SET @Sales = 10 WHILE @DayCount < 5000 BEGIN INSERT Sale VALUES (@DayCount,@Sales) SET @DayCount = @DayCount + 1 SET @Sales = @Sales + 15 END Next create a stored procedure to calculate the running total, and return a specified number of rows from the Sale table, using the following script: USE [CacheSample] GO SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO -- ============================================= -- Author: Robin -- Create date: -- Description: -- ============================================= CREATE PROCEDURE [dbo].[spGetRunningTotals] -- Add the parameters for the stored procedure here @HighestDayCount smallint = null AS BEGIN -- SET NOCOUNT ON added to prevent extra result sets from -- interfering with SELECT statements. SET NOCOUNT ON; IF @HighestDayCount IS NULL SELECT @HighestDayCount = MAX(DayCount) FROM dbo.Sale DECLARE @SaleTbl TABLE (DayCount smallint, Sales money, RunningTotal money) DECLARE @DayCount smallint, @Sales money, @RunningTotal money SET @RunningTotal = 0 SET @DayCount = 0 DECLARE rt_cursor CURSOR FOR SELECT DayCount, Sales FROM Sale ORDER BY DayCount OPEN rt_cursor FETCH NEXT FROM rt_cursor INTO @DayCount,@Sales WHILE @@FETCH_STATUS = 0 AND @DayCount <= @HighestDayCount BEGIN SET @RunningTotal = @RunningTotal + @Sales INSERT @SaleTbl VALUES (@DayCount,@Sales,@RunningTotal) FETCH NEXT FROM rt_cursor INTO @DayCount,@Sales END CLOSE rt_cursor DEALLOCATE rt_cursor SELECT DayCount, Sales, RunningTotal FROM @SaleTbl END GO Create the Sample ASP.NET application In Visual Studio create a new solution and add a class library project called CacheSample.BusinessObjects and an ASP.NET web application called CacheSample.UI. The CacheSample.BusinessObjects project will contain a single class to represent a Sale data item, with all the code to retrieve the sales from the database included in it for simplicity (normally I would at least have a separate Repository or other object that is responsible for retrieving data, and probably a data access layer as well, but for this sample I want to keep it simple). The C# code for the Sale class is shown below: using System; using System.Collections.Generic; using System.Data; using System.Data.SqlClient; namespace CacheSample.BusinessObjects { public class Sale { public Int16 DayCount { get; set; } public decimal Sales { get; set; } public decimal RunningTotal { get; set; } public static IEnumerable<Sale> GetSales(int? highestDayCount) { List<Sale> sales = new List<Sale>(); SqlParameter highestDayCountParameter = new SqlParameter("@HighestDayCount", SqlDbType.SmallInt); if (highestDayCount.HasValue) highestDayCountParameter.Value = highestDayCount; else highestDayCountParameter.Value = DBNull.Value; string connectionStr = System.Configuration.ConfigurationManager .ConnectionStrings["CacheSample"].ConnectionString; using(SqlConnection sqlConn = new SqlConnection(connectionStr)) using (SqlCommand sqlCmd = sqlConn.CreateCommand()) { sqlCmd.CommandText = "spGetRunningTotals"; sqlCmd.CommandType = CommandType.StoredProcedure; sqlCmd.Parameters.Add(highestDayCountParameter); sqlConn.Open(); using (SqlDataReader dr = sqlCmd.ExecuteReader()) { while (dr.Read()) { Sale newSale = new Sale(); newSale.DayCount = dr.GetInt16(0); newSale.Sales = dr.GetDecimal(1); newSale.RunningTotal = dr.GetDecimal(2); sales.Add(newSale); } } } return sales; } } } The static GetSale() method makes a call to the spGetRunningTotals stored procedure and then reads each row from the returned SqlDataReader into an instance of the Sale class, it then returns a List of the Sale objects, as IEnnumerable<Sale>. A reference to System.Configuration needs to be added to the CacheSample.BusinessObjects project so that the connection string can be read from the web.config file. In the CacheSample.UI ASP.NET project, create a single web page called ShowSales.aspx, and make this the default start up page. This page will contain a single button to call the GetSales() method and a label to display the results. The html mark up and the C# code behind are shown below: ShowSales.aspx <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="ShowSales.aspx.cs" Inherits="CacheSample.UI.ShowSales" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title>Cache Sample - Show All Sales</title> </head> <body> <form id="form1" runat="server"> <div> <asp:Button ID="btnTest1" runat="server" onclick="btnTest1_Click" Text="Get All Sales" />     <asp:Label ID="lblResults" runat="server"></asp:Label> </div> </form> </body> </html> ShowSales.aspx.cs using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; using CacheSample.BusinessObjects; namespace CacheSample.UI { public partial class ShowSales : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { } protected void btnTest1_Click(object sender, EventArgs e) { System.Diagnostics.Stopwatch stopWatch = new System.Diagnostics.Stopwatch(); stopWatch.Start(); var sales = Sale.GetSales(null); var lastSales = sales.Last(); stopWatch.Stop(); lblResults.Text = string.Format( "Count of Sales: {0}, Last DayCount: {1}, Total Sales: {2}. Query took {3} ms", sales.Count(), lastSales.DayCount, lastSales.RunningTotal, stopWatch.ElapsedMilliseconds); } } } Finally we need to add a connection string to the CacheSample SQL Server database, called CacheSample, to the web.config file: <?xmlversion="1.0"?> <configuration> <connectionStrings> <addname="CacheSample" connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;Initial Catalog=CacheSample" providerName="System.Data.SqlClient" /> </connectionStrings> <system.web> <compilationdebug="true"targetFramework="4.0" /> </system.web> </configuration> Run the application and click the button a few times to see how long each call to the database takes. On my system, each query takes about 450ms. Next I shall look at a solution to use the ASP.NET caching to cache the data returned by the query, so that subsequent requests to the GetSales() method are much faster. Adding Data Caching Support I am going to create my caching support in a separate project called CacheSample.Caching, so the next step is to add a class library to the solution. We shall be using the application configuration to define the implementation of our caching system, so we need a reference to System.Configuration adding to the project. ICacheProvider<T> Interface The first step in adding caching to our application is to define an interface, called ICacheProvider, in the CacheSample.Caching project, with methods to retrieve any data from the cache or to retrieve the data from the data source if it is not present in the cache. Dependency Injection will then be used to inject an implementation of this interface at runtime, allowing the users of the interface (i.e. the CacheSample.BusinessObjects project) to be completely unaware of how the caching is actually implemented. As data of any type maybe retrieved from the data source, it makes sense to use generics in the interface, with a generic type parameter defining the data type associated with a particular instance of the cache interface implementation. The C# code for the ICacheProvider interface is shown below: using System; using System.Collections.Generic; namespace CacheSample.Caching { public interface ICacheProvider { } public interface ICacheProvider<T> : ICacheProvider { T Fetch(string key, Func<T> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry); IEnumerable<T> Fetch(string key, Func<IEnumerable<T>> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry); } } The empty non-generic interface will be used as a type in a Dictionary generic collection later to store instances of the ICacheProvider<T> implementation for reuse, I prefer to use a base interface when doing this, as I think the alternative of using object makes for less clear code. The ICacheProvider<T> interface defines two overloaded Fetch methods, the difference between these is that one will return a single instance of the type T and the other will return an IEnumerable<T>, providing support for easy caching of collections of data items. Both methods will take a key parameter, which will uniquely identify the cached data, a delegate of type Func<T> or Func<IEnumerable<T>> which will provide the code to retrieve the data from the store if it is not present in the cache, and absolute or relative expiry policies to define when a cached item should expire. Note that at present there is no support for cache dependencies, but I shall be showing a method of adding this in part two of this article. CacheProviderFactory Class We need a mechanism of creating instances of our ICacheProvider<T> interface, using Dependency Injection to get the implementation of the interface. To do this we shall create a CacheProviderFactory static class in the CacheSample.Caching project. This factory will provide a generic static method called GetCacheProvider<T>(), which shall return instances of ICacheProvider<T>. We can then call this factory method with the relevant data type (for example the Sale class in the CacheSample.BusinessObject project) to get a instance of ICacheProvider for that type (e.g. call CacheProviderFactory.GetCacheProvider<Sale>() to get the ICacheProvider<Sale> implementation). The C# code for the CacheProviderFactory is shown below: using System; using System.Collections.Generic; using CacheSample.Caching.Configuration; namespace CacheSample.Caching { public static class CacheProviderFactory { private static Dictionary<Type, ICacheProvider> cacheProviders = new Dictionary<Type, ICacheProvider>(); private static object syncRoot = new object(); ///<summary> /// Factory method to create or retrieve an implementation of the /// ICacheProvider interface for type <typeparamref name="T"/>. ///</summary> ///<typeparam name="T"> /// The type that this cache provider instance will work with ///</typeparam> ///<returns>An instance of the implementation of ICacheProvider for type ///<typeparamref name="T"/>, as specified by the application /// configuration</returns> public static ICacheProvider<T> GetCacheProvider<T>() { ICacheProvider<T> cacheProvider = null; // Get the Type reference for the type parameter T Type typeOfT = typeof(T); // Lock the access to the cacheProviders dictionary // so multiple threads can work with it lock (syncRoot) { // First check if an instance of the ICacheProvider implementation // already exists in the cacheProviders dictionary for the type T if (cacheProviders.ContainsKey(typeOfT)) cacheProvider = (ICacheProvider<T>)cacheProviders[typeOfT]; else { // There is not already an instance of the ICacheProvider in // cacheProviders for the type T // so we need to create one // Get the Type reference for the application's implementation of // ICacheProvider from the configuration Type cacheProviderType = Type.GetType(CacheProviderConfigurationSection.Current. CacheProviderType); if (cacheProviderType != null) { // Now get a Type reference for the Cache Provider with the // type T generic parameter Type typeOfCacheProviderTypeForT = cacheProviderType.MakeGenericType(new Type[] { typeOfT }); if (typeOfCacheProviderTypeForT != null) { // Create the instance of the Cache Provider and add it to // the cacheProviders dictionary for future use cacheProvider = (ICacheProvider<T>)Activator. CreateInstance(typeOfCacheProviderTypeForT); cacheProviders.Add(typeOfT, cacheProvider); } } } } return cacheProvider; } } } As this code uses Activator.CreateInstance() to create instances of the ICacheProvider<T> implementation, which is a slow process, the factory class maintains a Dictionary of the previously created instances so that a cache provider needs to be created only once for each type. The type of the implementation of ICacheProvider<T> is read from a custom configuration section in the application configuration file, via the CacheProviderConfigurationSection class, which is described below. CacheProviderConfigurationSection Class The implementation of ICacheProvider<T> will be specified in a custom configuration section in the application’s configuration. To handle this create a folder in the CacheSample.Caching project called Configuration, and add a class called CacheProviderConfigurationSection to this folder. This class will extend the System.Configuration.ConfigurationSection class, and will contain a single string property called CacheProviderType. The C# code for this class is shown below: using System; using System.Configuration; namespace CacheSample.Caching.Configuration { internal class CacheProviderConfigurationSection : ConfigurationSection { public static CacheProviderConfigurationSection Current { get { return (CacheProviderConfigurationSection) ConfigurationManager.GetSection("cacheProvider"); } } [ConfigurationProperty("type", IsRequired=true)] public string CacheProviderType { get { return (string)this["type"]; } } } } Adding Data Caching to the Sales Class We now have enough code in place to add caching to the GetSales() method in the CacheSample.BusinessObjects.Sale class, even though we do not yet have an implementation of the ICacheProvider<T> interface. We need to add a reference to the CacheSample.Caching project to CacheSample.BusinessObjects so that we can use the ICacheProvider<T> interface within the GetSales() method. Once the reference is added, we can first create a unique string key based on the method name and the parameter value, so that the same cache key is used for repeated calls to the method with the same parameter values. Then we get an instance of the cache provider for the Sales type, using the CacheProviderFactory, and pass the existing code to retrieve the data from the database as the retrievalMethod delegate in a call to the Cache Provider Fetch() method. The C# code for the modified GetSales() method is shown below: public static IEnumerable<Sale> GetSales(int? highestDayCount) { string cacheKey = string.Format("CacheSample.BusinessObjects.GetSalesWithCache({0})", highestDayCount); return CacheSample.Caching.CacheProviderFactory. GetCacheProvider<Sale>().Fetch(cacheKey, delegate() { List<Sale> sales = new List<Sale>(); SqlParameter highestDayCountParameter = new SqlParameter("@HighestDayCount", SqlDbType.SmallInt); if (highestDayCount.HasValue) highestDayCountParameter.Value = highestDayCount; else highestDayCountParameter.Value = DBNull.Value; string connectionStr = System.Configuration.ConfigurationManager. ConnectionStrings["CacheSample"].ConnectionString; using (SqlConnection sqlConn = new SqlConnection(connectionStr)) using (SqlCommand sqlCmd = sqlConn.CreateCommand()) { sqlCmd.CommandText = "spGetRunningTotals"; sqlCmd.CommandType = CommandType.StoredProcedure; sqlCmd.Parameters.Add(highestDayCountParameter); sqlConn.Open(); using (SqlDataReader dr = sqlCmd.ExecuteReader()) { while (dr.Read()) { Sale newSale = new Sale(); newSale.DayCount = dr.GetInt16(0); newSale.Sales = dr.GetDecimal(1); newSale.RunningTotal = dr.GetDecimal(2); sales.Add(newSale); } } } return sales; }, null, new TimeSpan(0, 10, 0)); } This example passes the code to retrieve the Sales data from the database to the Cache Provider as an anonymous method, however it could also be written as a lambda. The main advantage of using an anonymous function (method or lambda) is that the code inside the anonymous function can access the parameters passed to the GetSales() method. Finally the absolute expiry is set to null, and the relative expiry set to 10 minutes, to indicate that the cache entry should be removed 10 minutes after the last request for the data. As the ICacheProvider<T> has a Fetch() method that returns IEnumerable<T>, we can simply return the results of the Fetch() method to the caller of the GetSales() method. This should be all that is needed for the GetSales() method to now retrieve data from a cache after the first time the data has be retrieved from the database. Implementing a ASP.NET Cache Provider The final step is to actually implement the ICacheProvider<T> interface, and add the implementation details to the web.config file for the dependency injection. The cache provider implementation needs to have access to System.Web. Therefore it could be placed in the CacheSample.UI project, or in its own project that has a reference to System.Web. Implementing the Cache Provider in a separate project is my favoured approach. Create a new project inside the solution called CacheSample.CacheProvider, and add references to System.Web and CacheSample.Caching to this project. Add a class to the project called AspNetCacheProvider. Make the class a generic class by adding the generic parameter <T> and indicate that the class implements ICacheProvider<T>. The C# code for the AspNetCacheProvider class is shown below: using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Caching; using CacheSample.Caching; namespace CacheSample.CacheProvider { public class AspNetCacheProvider<T> : ICacheProvider<T> { #region ICacheProvider<T> Members public T Fetch(string key, Func<T> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry) { return FetchAndCache<T>(key, retrieveData, absoluteExpiry, relativeExpiry); } public IEnumerable<T> Fetch(string key, Func<IEnumerable<T>> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry) { return FetchAndCache<IEnumerable<T>>(key, retrieveData, absoluteExpiry, relativeExpiry); } #endregion #region Helper Methods private U FetchAndCache<U>(string key, Func<U> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry) { U value; if (!TryGetValue<U>(key, out value)) { value = retrieveData(); if (!absoluteExpiry.HasValue) absoluteExpiry = Cache.NoAbsoluteExpiration; if (!relativeExpiry.HasValue) relativeExpiry = Cache.NoSlidingExpiration; HttpContext.Current.Cache.Insert(key, value, null, absoluteExpiry.Value, relativeExpiry.Value); } return value; } private bool TryGetValue<U>(string key, out U value) { object cachedValue = HttpContext.Current.Cache.Get(key); if (cachedValue == null) { value = default(U); return false; } else { try { value = (U)cachedValue; return true; } catch { value = default(U); return false; } } } #endregion } } The two interface Fetch() methods call a private method called FetchAndCache(). This method first checks for a element in the HttpContext.Current.Cache with the specified cache key, and if so tries to cast this to the specified type (either T or IEnumerable<T>). If the cached element is found, the FetchAndCache() method simply returns it. If it is not found in the cache, the method calls the retrievalMethod delegate to get the data from the data source, and then adds this to the HttpContext.Current.Cache. The final step is to add the AspNetCacheProvider class to the relevant custom configuration section in the CacheSample.UI.Web.Config file. To do this there needs to be a <configSections> element added as the first element in <configuration>. This will match a custom section called <cacheProvider> with the CacheProviderConfigurationSection. Then we add a <cacheProvider> element, with a type property set to the fully qualified assembly name of the AspNetCacheProvider class, as shown below: <?xmlversion="1.0"?> <configuration> <configSections> <sectionname="cacheProvider" type="CacheSample.Base.Configuration.CacheProviderConfigurationSection, CacheSample.Base" /> </configSections> <connectionStrings> <addname="CacheSample" connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;Initial Catalog=CacheSample" providerName="System.Data.SqlClient" /> </connectionStrings> <cacheProvidertype="CacheSample.CacheProvider.AspNetCacheProvider`1, CacheSample.CacheProvider, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"> </cacheProvider> <system.web> <compilationdebug="true"targetFramework="4.0" /> </system.web> </configuration> One point to note is that the fully qualified assembly name of the AspNetCacheProvider class includes the notation `1 after the class name, which indicates that it is a generic class with a single generic type parameter. The CacheSample.UI project needs to have references added to CacheSample.Caching and CacheSample.CacheProvider so that the actual application is aware of the relevant cache provider implementation. Conclusion After implementing this solution, you should have a working cache provider mechanism, that will allow the middle and data access layers to implement caching support when retrieving data, without any knowledge of the actually caching implementation. If the UI is not ASP.NET based, if for example it is Winforms or WPF, the implementation of ICacheProvider<T> would be written around whatever technology is available. It could even be a standalone caching system that takes full responsibility for adding and removing items from a global store. The next part of this article will show how this caching mechanism may be extended to provide support for cache dependencies, such as the System.Web.Caching.SqlCacheDependency. Another possible extension would be to cache the cache provider implementations instead of storing them in a static Dictionary in the CacheProviderFactory. This would prevent a build up of seldom used cache providers in the application memory, as they could be removed from the cache if not used often enough, although in reality there are probably unlikely to be vast numbers of cache provider implementation instances, as most applications do not have a massive number of business object or model types.

Read the article

C#/.NET Little Wonders: The Generic Func Delegates

- by James Michael Hare

Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Back in one of my three original “Little Wonders” Trilogy of posts, I had listed generic delegates as one of the Little Wonders of .NET. Later, someone posted a comment saying said that they would love more detail on the generic delegates and their uses, since my original entry just scratched the surface of them. Last week, I began our look at some of the handy generic delegates built into .NET with a description of delegates in general, and the Action family of delegates. For this week, I’ll launch into a look at the Func family of generic delegates and how they can be used to support generic, reusable algorithms and classes. Quick Delegate Recap Delegates are similar to function pointers in C++ in that they allow you to store a reference to a method. They can store references to either static or instance methods, and can actually be used to chain several methods together in one delegate. Delegates are very type-safe and can be satisfied with any standard method, anonymous method, or a lambda expression. They can also be null as well (refers to no method), so care should be taken to make sure that the delegate is not null before you invoke it. Delegates are defined using the keyword delegate, where the delegate’s type name is placed where you would typically place the method name: 1: // This delegate matches any method that takes string, returns nothing 2: public delegate void Log(string message); This delegate defines a delegate type named Log that can be used to store references to any method(s) that satisfies its signature (whether instance, static, lambda expression, etc.). Delegate instances then can be assigned zero (null) or more methods using the operator = which replaces the existing delegate chain, or by using the operator += which adds a method to the end of a delegate chain: 1: // creates a delegate instance named currentLogger defaulted to Console.WriteLine (static method) 2: Log currentLogger = Console.Out.WriteLine; 3: 4: // invokes the delegate, which writes to the console out 5: currentLogger("Hi Standard Out!"); 6: 7: // append a delegate to Console.Error.WriteLine to go to std error 8: currentLogger += Console.Error.WriteLine; 9: 10: // invokes the delegate chain and writes message to std out and std err 11: currentLogger("Hi Standard Out and Error!"); While delegates give us a lot of power, it can be cumbersome to re-create fairly standard delegate definitions repeatedly, for this purpose the generic delegates were introduced in various stages in .NET. These support various method types with particular signatures. Note: a caveat with generic delegates is that while they can support multiple parameters, they do not match methods that contains ref or out parameters. If you want to a delegate to represent methods that takes ref or out parameters, you will need to create a custom delegate. We’ve got the Func… delegates Just like it’s cousin, the Action delegate family, the Func delegate family gives us a lot of power to use generic delegates to make classes and algorithms more generic. Using them keeps us from having to define a new delegate type when need to make a class or algorithm generic. Remember that the point of the Action delegate family was to be able to perform an “action” on an item, with no return results. Thus Action delegates can be used to represent most methods that take 0 to 16 arguments but return void. You can assign a method The Func delegate family was introduced in .NET 3.5 with the advent of LINQ, and gives us the power to define a function that can be called on 0 to 16 arguments and returns a result. Thus, the main difference between Action and Func, from a delegate perspective, is that Actions return nothing, but Funcs return a result. The Func family of delegates have signatures as follows: Func<TResult> – matches a method that takes no arguments, and returns value of type TResult. Func<T, TResult> – matches a method that takes an argument of type T, and returns value of type TResult. Func<T1, T2, TResult> – matches a method that takes arguments of type T1 and T2, and returns value of type TResult. Func<T1, T2, …, TResult> – and so on up to 16 arguments, and returns value of type TResult. These are handy because they quickly allow you to be able to specify that a method or class you design will perform a function to produce a result as long as the method you specify meets the signature. For example, let’s say you were designing a generic aggregator, and you wanted to allow the user to define how the values will be aggregated into the result (i.e. Sum, Min, Max, etc…). To do this, we would ask the user of our class to pass in a method that would take the current total, the next value, and produce a new total. A class like this could look like: 1: public sealed class Aggregator<TValue, TResult> 2: { 3: // holds method that takes previous result, combines with next value, creates new result 4: private Func<TResult, TValue, TResult> _aggregationMethod; 5: 6: // gets or sets the current result of aggregation 7: public TResult Result { get; private set; } 8: 9: // construct the aggregator given the method to use to aggregate values 10: public Aggregator(Func<TResult, TValue, TResult> aggregationMethod = null) 11: { 12: if (aggregationMethod == null) throw new ArgumentNullException("aggregationMethod"); 13: 14: _aggregationMethod = aggregationMethod; 15: } 16: 17: // method to add next value 18: public void Aggregate(TValue nextValue) 19: { 20: // performs the aggregation method function on the current result and next and sets to current result 21: Result = _aggregationMethod(Result, nextValue); 22: } 23: } Of course, LINQ already has an Aggregate extension method, but that works on a sequence of IEnumerable<T>, whereas this is designed to work more with aggregating single results over time (such as keeping track of a max response time for a service). We could then use this generic aggregator to find the sum of a series of values over time, or the max of a series of values over time (among other things): 1: // creates an aggregator that adds the next to the total to sum the values 2: var sumAggregator = new Aggregator<int, int>((total, next) => total + next); 3: 4: // creates an aggregator (using static method) that returns the max of previous result and next 5: var maxAggregator = new Aggregator<int, int>(Math.Max); So, if we were timing the response time of a web method every time it was called, we could pass that response time to both of these aggregators to get an idea of the total time spent in that web method, and the max time spent in any one call to the web method: 1: // total will be 13 and max 13 2: int responseTime = 13; 3: sumAggregator.Aggregate(responseTime); 4: maxAggregator.Aggregate(responseTime); 5: 6: // total will be 20 and max still 13 7: responseTime = 7; 8: sumAggregator.Aggregate(responseTime); 9: maxAggregator.Aggregate(responseTime); 10: 11: // total will be 40 and max now 20 12: responseTime = 20; 13: sumAggregator.Aggregate(responseTime); 14: maxAggregator.Aggregate(responseTime); The Func delegate family is useful for making generic algorithms and classes, and in particular allows the caller of the method or user of the class to specify a function to be performed in order to generate a result. What is the result of a Func delegate chain? If you remember, we said earlier that you can assign multiple methods to a delegate by using the += operator to chain them. So how does this affect delegates such as Func that return a value, when applied to something like the code below? 1: Func<int, int, int> combo = null; 2: 3: // What if we wanted to aggregate the sum and max together? 4: combo += (total, next) => total + next; 5: combo += Math.Max; 6: 7: // what is the result? 8: var comboAggregator = new Aggregator<int, int>(combo); Well, in .NET if you chain multiple methods in a delegate, they will all get invoked, but the result of the delegate is the result of the last method invoked in the chain. Thus, this aggregator would always result in the Math.Max() result. The other chained method (the sum) gets executed first, but it’s result is thrown away: 1: // result is 13 2: int responseTime = 13; 3: comboAggregator.Aggregate(responseTime); 4: 5: // result is still 13 6: responseTime = 7; 7: comboAggregator.Aggregate(responseTime); 8: 9: // result is now 20 10: responseTime = 20; 11: comboAggregator.Aggregate(responseTime); So remember, you can chain multiple Func (or other delegates that return values) together, but if you do so you will only get the last executed result. Func delegates and co-variance/contra-variance in .NET 4.0 Just like the Action delegate, as of .NET 4.0, the Func delegate family is contra-variant on its arguments. In addition, it is co-variant on its return type. To support this, in .NET 4.0 the signatures of the Func delegates changed to: Func<out TResult> – matches a method that takes no arguments, and returns value of type TResult (or a more derived type). Func<in T, out TResult> – matches a method that takes an argument of type T (or a less derived type), and returns value of type TResult(or a more derived type). Func<in T1, in T2, out TResult> – matches a method that takes arguments of type T1 and T2 (or less derived types), and returns value of type TResult (or a more derived type). Func<in T1, in T2, …, out TResult> – and so on up to 16 arguments, and returns value of type TResult (or a more derived type). Notice the addition of the in and out keywords before each of the generic type placeholders. As we saw last week, the in keyword is used to specify that a generic type can be contra-variant -- it can match the given type or a type that is less derived. However, the out keyword, is used to specify that a generic type can be co-variant -- it can match the given type or a type that is more derived. On contra-variance, if you are saying you need an function that will accept a string, you can just as easily give it an function that accepts an object. In other words, if you say “give me an function that will process dogs”, I could pass you a method that will process any animal, because all dogs are animals. On the co-variance side, if you are saying you need a function that returns an object, you can just as easily pass it a function that returns a string because any string returned from the given method can be accepted by a delegate expecting an object result, since string is more derived. Once again, in other words, if you say “give me a method that creates an animal”, I can pass you a method that will create a dog, because all dogs are animals. It really all makes sense, you can pass a more specific thing to a less specific parameter, and you can return a more specific thing as a less specific result. In other words, pay attention to the direction the item travels (parameters go in, results come out). Keeping that in mind, you can always pass more specific things in and return more specific things out. For example, in the code below, we have a method that takes a Func<object> to generate an object, but we can pass it a Func<string> because the return type of object can obviously accept a return value of string as well: 1: // since Func<object> is co-variant, this will access Func<string>, etc... 2: public static string Sequence(int count, Func<object> generator) 3: { 4: var builder = new StringBuilder(); 5: 6: for (int i=0; i<count; i++) 7: { 8: object value = generator(); 9: builder.Append(value); 10: } 11: 12: return builder.ToString(); 13: } Even though the method above takes a Func<object>, we can pass a Func<string> because the TResult type placeholder is co-variant and accepts types that are more derived as well: 1: // delegate that's typed to return string. 2: Func<string> stringGenerator = () => DateTime.Now.ToString(); 3: 4: // This will work in .NET 4.0, but not in previous versions 5: Sequence(100, stringGenerator); Previous versions of .NET implemented some forms of co-variance and contra-variance before, but .NET 4.0 goes one step further and allows you to pass or assign an Func<A, BResult> to a Func<Y, ZResult> as long as A is less derived (or same) as Y, and BResult is more derived (or same) as ZResult. Sidebar: The Func and the Predicate A method that takes one argument and returns a bool is generally thought of as a predicate. Predicates are used to examine an item and determine whether that item satisfies a particular condition. Predicates are typically unary, but you may also have binary and other predicates as well. Predicates are often used to filter results, such as in the LINQ Where() extension method: 1: var numbers = new[] { 1, 2, 4, 13, 8, 10, 27 }; 2: 3: // call Where() using a predicate which determines if the number is even 4: var evens = numbers.Where(num => num % 2 == 0); As of .NET 3.5, predicates are typically represented as Func<T, bool> where T is the type of the item to examine. Previous to .NET 3.5, there was a Predicate<T> type that tended to be used (which we’ll discuss next week) and is still supported, but most developers recommend using Func<T, bool> now, as it prevents confusion with overloads that accept unary predicates and binary predicates, etc.: 1: // this seems more confusing as an overload set, because of Predicate vs Func 2: public static SomeMethod(Predicate<int> unaryPredicate) { } 3: public static SomeMethod(Func<int, int, bool> binaryPredicate) { } 4: 5: // this seems more consistent as an overload set, since just uses Func 6: public static SomeMethod(Func<int, bool> unaryPredicate) { } 7: public static SomeMethod(Func<int, int, bool> binaryPredicate) { } Also, even though Predicate<T> and Func<T, bool> match the same signatures, they are separate types! Thus you cannot assign a Predicate<T> instance to a Func<T, bool> instance and vice versa: 1: // the same method, lambda expression, etc can be assigned to both 2: Predicate<int> isEven = i => (i % 2) == 0; 3: Func<int, bool> alsoIsEven = i => (i % 2) == 0; 4: 5: // but the delegate instances cannot be directly assigned, strongly typed! 6: // ERROR: cannot convert type... 7: isEven = alsoIsEven; 8: 9: // however, you can assign by wrapping in a new instance: 10: isEven = new Predicate<int>(alsoIsEven); 11: alsoIsEven = new Func<int, bool>(isEven); So, the general advice that seems to come from most developers is that Predicate<T> is still supported, but we should use Func<T, bool> for consistency in .NET 3.5 and above. Sidebar: Func as a Generator for Unit Testing One area of difficulty in unit testing can be unit testing code that is based on time of day. We’d still want to unit test our code to make sure the logic is accurate, but we don’t want the results of our unit tests to be dependent on the time they are run. One way (of many) around this is to create an internal generator that will produce the “current” time of day. This would default to returning result from DateTime.Now (or some other method), but we could inject specific times for our unit testing. Generators are typically methods that return (generate) a value for use in a class/method. For example, say we are creating a CacheItem<T> class that represents an item in the cache, and we want to make sure the item shows as expired if the age is more than 30 seconds. Such a class could look like: 1: // responsible for maintaining an item of type T in the cache 2: public sealed class CacheItem<T> 3: { 4: // helper method that returns the current time 5: private static Func<DateTime> _timeGenerator = () => DateTime.Now; 6: 7: // allows internal access to the time generator 8: internal static Func<DateTime> TimeGenerator 9: { 10: get { return _timeGenerator; } 11: set { _timeGenerator = value; } 12: } 13: 14: // time the item was cached 15: public DateTime CachedTime { get; private set; } 16: 17: // the item cached 18: public T Value { get; private set; } 19: 20: // item is expired if older than 30 seconds 21: public bool IsExpired 22: { 23: get { return _timeGenerator() - CachedTime > TimeSpan.FromSeconds(30.0); } 24: } 25: 26: // creates the new cached item, setting cached time to "current" time 27: public CacheItem(T value) 28: { 29: Value = value; 30: CachedTime = _timeGenerator(); 31: } 32: } Then, we can use this construct to unit test our CacheItem<T> without any time dependencies: 1: var baseTime = DateTime.Now; 2: 3: // start with current time stored above (so doesn't drift) 4: CacheItem<int>.TimeGenerator = () => baseTime; 5: 6: var target = new CacheItem<int>(13); 7: 8: // now add 15 seconds, should still be non-expired 9: CacheItem<int>.TimeGenerator = () => baseTime.AddSeconds(15); 10: 11: Assert.IsFalse(target.IsExpired); 12: 13: // now add 31 seconds, should now be expired 14: CacheItem<int>.TimeGenerator = () => baseTime.AddSeconds(31); 15: 16: Assert.IsTrue(target.IsExpired); Now we can unit test for 1 second before, 1 second after, 1 millisecond before, 1 day after, etc. Func delegates can be a handy tool for this type of value generation to support more testable code. Summary Generic delegates give us a lot of power to make truly generic algorithms and classes. The Func family of delegates is a great way to be able to specify functions to calculate a result based on 0-16 arguments. Stay tuned in the weeks that follow for other generic delegates in the .NET Framework! Tweet Technorati Tags: .NET, C#, CSharp, Little Wonders, Generics, Func, Delegates

Read the article

Mulit-tenant ASP.NET MVC – Controllers

- by zowens

Part I – Introduction Part II – Foundation The time has come to talk about controllers in a multi-tenant ASP.NET MVC architecture. This is actually the most critical design decision you will make when dealing with multi-tenancy with MVC. In my design, I took into account the design goals I mentioned in the introduction about inversion of control and what a tenant is to my design. Be aware that this is only one way to achieve multi-tenant controllers. The Premise MvcEx (which is a sample written by Rob Ashton) utilizes dynamic controllers. Essentially a controller is “dynamic” in that multiple action results can be placed in different “controllers” with the same name. This approach is a bit too complicated for my design. I wanted to stick with plain old inheritance when dealing with controllers. The basic premise of my controller design is that my main host defines a set of universal controllers. It is the responsibility of the tenant to decide if the tenant would like to utilize these core controllers. This can be done either by straight usage of the controller or inheritance for extension of the functionality defined by the controller. The controller is resolved by a StructureMap container that is attached to the tenant, as discussed in Part II. Controller Resolution I have been thinking about two different ways to resolve controllers with StructureMap. One way is to use named instances. This is a really easy way to simply pull the controller right out of the container without a lot of fuss. I ultimately chose not to use this approach. The reason for this decision is to ensure that the controllers are named properly. If a controller has a different named instance that the controller type, then the resolution has a significant disconnect and there are no guarantees. The final approach, the one utilized by the sample, is to simply pull all controller types and correlate the type with a controller name. This has a bit of a application start performance disadvantage, but is significantly more approachable for maintainability. For example, if I wanted to go back and add a “ControllerName” attribute, I would just have to change the ControllerFactory to suit my needs. The Code The container factory that I have built is actually pretty simple. That’s really all we need. The most significant method is the GetControllersFor method. This method makes the model from the Container and determines all the concrete types for IController. The thing you might notice is that this doesn’t depend on tenants, but rather containers. You could easily use this controller factory for an application that doesn’t utilize multi-tenancy. public class ContainerControllerFactory : IControllerFactory { private readonly ThreadSafeDictionary<IContainer, IDictionary<string, Type>> typeCache; public ContainerControllerFactory(IContainerResolver resolver) { Ensure.Argument.NotNull(resolver, "resolver"); this.ContainerResolver = resolver; this.typeCache = new ThreadSafeDictionary<IContainer, IDictionary<string, Type>>(); } public IContainerResolver ContainerResolver { get; private set; } public virtual IController CreateController(RequestContext requestContext, string controllerName) { var controllerType = this.GetControllerType(requestContext, controllerName); if (controllerType == null) return null; var controller = this.ContainerResolver.Resolve(requestContext).GetInstance(controllerType) as IController; // ensure the action invoker is a ContainerControllerActionInvoker if (controller != null && controller is Controller && !((controller as Controller).ActionInvoker is ContainerControllerActionInvoker)) (controller as Controller).ActionInvoker = new ContainerControllerActionInvoker(this.ContainerResolver); return controller; } public void ReleaseController(IController controller) { if (controller != null && controller is IDisposable) ((IDisposable)controller).Dispose(); } internal static IEnumerable<Type> GetControllersFor(IContainer container) { Ensure.Argument.NotNull(container); return container.Model.InstancesOf<IController>().Select(x => x.ConcreteType).Distinct(); } protected virtual Type GetControllerType(RequestContext requestContext, string controllerName) { Ensure.Argument.NotNull(requestContext, "requestContext"); Ensure.Argument.NotNullOrEmpty(controllerName, "controllerName"); var container = this.ContainerResolver.Resolve(requestContext); var typeDictionary = this.typeCache.GetOrAdd(container, () => GetControllersFor(container).ToDictionary(x => ControllerFriendlyName(x.Name))); Type found = null; if (typeDictionary.TryGetValue(ControllerFriendlyName(controllerName), out found)) return found; return null; } private static string ControllerFriendlyName(string value) { return (value ?? string.Empty).ToLowerInvariant().Without("controller"); } } One thing to note about my implementation is that we do not use namespaces that can be utilized in the default ASP.NET MVC controller factory. This is something that I don’t use and have no desire to implement and test. The reason I am not using namespaces in this situation is because each tenant has its own namespaces and the routing would not make sense in this case. Because we are using IoC, dependencies are automatically injected into the constructor. For example, a tenant container could implement it’s own IRepository and a controller could be defined in the “main” project. The IRepository from the tenant would be injected into the main project’s controller. This is quite a useful feature. Again, the source code is on GitHub here. Up Next Up next is the view resolution. This is a complicated issue, so be prepared. I hope that you have found this series useful. If you have any questions about my implementation so far, send me an email or DM me on Twitter. I have had a lot of great conversations about multi-tenancy so far and I greatly appreciate the feedback!

Read the article

Integrating WIF with WCF Data Services

- by cibrax

A time ago I discussed how a custom REST Starter kit interceptor could be used to parse a SAML token in the Http Authorization header and wrap that into a ClaimsPrincipal that the WCF services could use. The thing is that code was initially created for Geneva framework, so it got deprecated quickly. I recently needed that piece of code for one of projects where I am currently working on so I decided to update it for WIF. As this interceptor can be injected in any host for WCF REST services, also represents an excellent solution for integrating claim-based security into WCF Data Services (previously known as ADO.NET Data Services). The interceptor basically expects a SAML token in the Authorization header. If a token is found, it is parsed and a new ClaimsPrincipal is initialized and injected in the WCF authorization context. public class SamlAuthenticationInterceptor : RequestInterceptor { SecurityTokenHandlerCollection handlers; public SamlAuthenticationInterceptor() : base(false) { this.handlers = FederatedAuthentication.ServiceConfiguration.SecurityTokenHandlers; } public override void ProcessRequest(ref RequestContext requestContext) { SecurityToken token = ExtractCredentials(requestContext.RequestMessage); if (token != null) { ClaimsIdentityCollection claims = handlers.ValidateToken(token); var principal = new ClaimsPrincipal(claims); InitializeSecurityContext(requestContext.RequestMessage, principal); } else { DenyAccess(ref requestContext); } } private void DenyAccess(ref RequestContext requestContext) { Message reply = Message.CreateMessage(MessageVersion.None, null); HttpResponseMessageProperty responseProperty = new HttpResponseMessageProperty() { StatusCode = HttpStatusCode.Unauthorized }; responseProperty.Headers.Add("WWW-Authenticate", String.Format("Basic realm=\"{0}\"", "")); reply.Properties[HttpResponseMessageProperty.Name] = responseProperty; requestContext.Reply(reply); requestContext = null; } private SecurityToken ExtractCredentials(Message requestMessage) { HttpRequestMessageProperty request = (HttpRequestMessageProperty) requestMessage.Properties[HttpRequestMessageProperty.Name]; string authHeader = request.Headers["Authorization"]; if (authHeader != null && authHeader.Contains("<saml")) { XmlTextReader xmlReader = new XmlTextReader(new StringReader(authHeader)); var col = SecurityTokenHandlerCollection.CreateDefaultSecurityTokenHandlerCollection(); SecurityToken token = col.ReadToken(xmlReader); return token; } return null; } private void InitializeSecurityContext(Message request, IPrincipal principal) { List<IAuthorizationPolicy> policies = new List<IAuthorizationPolicy>(); policies.Add(new PrincipalAuthorizationPolicy(principal)); ServiceSecurityContext securityContext = new ServiceSecurityContext(policies.AsReadOnly()); if (request.Properties.Security != null) { request.Properties.Security.ServiceSecurityContext = securityContext; } else { request.Properties.Security = new SecurityMessageProperty() { ServiceSecurityContext = securityContext }; } } class PrincipalAuthorizationPolicy : IAuthorizationPolicy { string id = Guid.NewGuid().ToString(); IPrincipal user; public PrincipalAuthorizationPolicy(IPrincipal user) { this.user = user; } public ClaimSet Issuer { get { return ClaimSet.System; } } public string Id { get { return this.id; } } public bool Evaluate(EvaluationContext evaluationContext, ref object state) { evaluationContext.AddClaimSet(this, new DefaultClaimSet(System.IdentityModel.Claims.Claim.CreateNameClaim(user.Identity.Name))); evaluationContext.Properties["Identities"] = new List<IIdentity>(new IIdentity[] { user.Identity }); evaluationContext.Properties["Principal"] = user; return true; } } A WCF Data Service, as any other WCF Service, contains a service host where this interceptor can be injected. The following code illustrates how that can be done in the “svc” file. <%@ ServiceHost Language="C#" Debug="true" Service="ContactsDataService" Factory="AppServiceHostFactory" %> using System; using System.ServiceModel; using System.ServiceModel.Activation; using Microsoft.ServiceModel.Web; class AppServiceHostFactory : ServiceHostFactory { protected override ServiceHost CreateServiceHost(Type serviceType, Uri[] baseAddresses) { WebServiceHost2 result = new WebServiceHost2(serviceType, true, baseAddresses); result.Interceptors.Add(new SamlAuthenticationInterceptor()); return result; } } WCF Data Services includes an specific WCF host of out the box (DataServiceHost). However, the service is not affected at all if you replace it with a custom one as I am doing in the code above (WebServiceHost2 is part of the REST Starter kit). Finally, the client application needs to pass the SAML token somehow to the data service. In case you are using any Http client library for consuming the data service, that’s easy to do, you only need to include the SAML token as part of the “Authorization” header. If you are using the auto-generated data service proxy, a little piece of code is needed to inject a SAML token into the DataServiceContext instance. That class provides an event “SendingRequest” that any client application can leverage to include custom code that modified the Http request before it is sent to the service. So, you can easily create an extension method for the DataServiceContext that negotiates the SAML token with an existing STS, and adds that token as part of the “Authorization” header. public static class DataServiceContextExtensions { public static void ConfigureFederatedCredentials(this DataServiceContext context, string baseStsAddress, string realm) { string address = string.Format(STSAddressFormat, baseStsAddress, realm); string token = NegotiateSecurityToken(address); context.SendingRequest += (source, args) => { args.RequestHeaders.Add("Authorization", token); }; } private string NegotiateSecurityToken(string address) { } } I left the NegociateSecurityToken method empty for this extension as it depends pretty much on how you are negotiating tokens from an existing STS. In case you want to end-to-end REST solution that involves an Http endpoint for the STS, you should definitely take a look at the Thinktecture starter STS project in codeplex.

Read the article

Physics in my game confused after restructuring the Game loop

- by Julian Assange

Hello! I'm on my way with making a game in Java. Now I have some trouble with an interpolation based game loop in my calculations. Before I used that system the calculation of a falling object was like this: Delta based system private static final float SPEED_OF_GRAVITY = 500.0f; @Override public void update(float timeDeltaSeconds, Object parentObject) { parentObject.y = parentObject.y + (parentObject.yVelocity * timeDeltaSeconds); parentObject.yVelocity -= SPEED_OF_GRAVITY * timeDeltaSeconds; ...... What you see here is that I used that delta value from previous frame to the current frame to calculate the physics. Now I switched and implement a interpolation based system and I actually left the current system where I used delta to calculate my physics. However, with the interpolation system the delta time is removed - but now are my calculations screwed up and I've tried the whole day to solve this: Interpolation based system private static final float SPEED_OF_GRAVITY = 500.0f; @Override public void update(Object parentObject) { parentObject.y = parentObject.y + (parentObject.yVelocity); parentObject.yVelocity -= SPEED_OF_GRAVITY; ...... I'm totally clueless - how should this be solved? The rendering part is solved with a simple prediction method. With the delta system I could see my object be smoothly rendered to the screen, but with this interpolation/prediction method the object just appear sticky for one second and then it's gone. The core of this game loop is actually from here deWiTTERS Game Loop, where I trying to implement the last solution he describes. Shortly - my physics are in a mess and this need to be solved. Any ideas? Thanks in advance!

Read the article

Free cloud web service development

- by hyde

I am looking for a free (as in beer) combination of services, for learning "cloud SW development" and very small scale private use (say, a private streamlined web shopping&todo list with simple auth). The combination should include the full set of needed services: DVCS service (like github) A cloud service to run the backend code A suitable data storage service (preferably not SQL), accessed by the backend (if not included in the backend service) A web service, serving the web pages seen by user, to access the backend functionality A "cloud IDE" (ideally one, two is ok too) for both backend and HTML/javascript coding If (backend) deployment uses some CI, then that Other points: Backend programming language can be anything, except VB or PHP Everything has to be in the cloud, nothing permanent on a local PC (graphics is not part of the question) Looking for ready-to-use service combination, not a virtual server where I can set anything up myself I don't care if service insists on displaying ads in the user web UI "Cheap" and "free trial" are ok too, if "free" does not exist As per example use case, storage, CPU and bandwidth quota requirements are negligible Google finds several services of course, all requiring at least registration before testing, so I'm looking for a known-good combination, so ideal answer starts with "I use this service combo: ...", contains links to services and brief description and personal experiences.

Read the article

[MINI HOW-TO] How To Use Bcc (Blind Carbon Copy) in Outlook 2010

- by Mysticgeek

If you want to send an email to a contact or several contacts, you might want to keep some of the recipient email addresses private using the Bcc (Blind Carbon Copy) Field. Here’s how to do it in Outlook 2010. It’s not enabled by default, but adding it as a field for all future emails is a simple process. Launch Outlook and under the Home tab click on the New E-mail button. When the new mail window opens click on the Options tab and in the Show Fields column select Bcc. The Bcc field will appear and you can then put the contacts in there who you want to receive the mail secretly or don’t want to show a certain email address. Now anytime you compose a message, the Bcc field is included. For more on the Bcc field check out the blog post from Mysticgeek – Keep Your Email Contacts Private. Similar Articles Productive Geek Tips How To Switch Back to Outlook 2007 After the 2010 Beta EndsOpen Different Outlook Features in Separate Windows to Improve ProductivityThursday’s Pre-Holiday Lazy Links RoundupCreate an Email Template in Outlook 2003Change Outlook Startup Folder TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Follow Finder Finds You Twitter Users To Follow Combine MP3 Files Easily QuicklyCode Provides Cheatsheets & Other Programming Stuff Download Free MP3s from Amazon Awe inspiring, inter-galactic theme (Win 7) Case Study – How to Optimize Popular Wordpress Sites

Read the article

EU Research for ICT - Call 7 - biggest ever at € 780 million

- by trond-arne.undheim

Under the Digital Agenda for Europe, the Commission has committed to maintaining the pace of a 20% yearly increase of the annual ICT R&D budget at least until 2013. The EU's flagship policy programme calls for doubling of annual public spending on ICT R&D by 2020 and to leverage an equivalent increase in private spending to achieve the goals of Europe's 2020 strategy for jobs and growth. Call 7 is one of the biggest calls ever launched for information and communications technology (ICT) research proposals under the EU's research framework programmes. It will result in project funding of € 780 million in 2011. This funding will advance research on the future internet, robotics, smart and embedded systems, photonics, ICT for energy efficiency, health and well-being in an ageing society, and more. The €780 million call for proposals is part of the biggest ever annual Work Programme under the EU's 7th Framework Programme for Research. Almost €1.2 billion has been budgeted for 2011. €220 million were made available already in July 2010 for public private partnerships focusing on ICT for smart cars, green buildings, sustainable factories and the future internet. Universities, research centres, SMEs, large companies and other organisations in Europe and beyond are eligible to apply for project funding under ICT Call 7. Proposals can be submitted until 18 January 2011, after which they will be evaluated by independent panels of experts for selection on the basis of their quality. Background: Digital Agenda: European Commission announces €780 million boost for strategic ICT research. Call text: ICT Call 7 Deadline: 18/01/2011.

Read the article

A Nondeterministic Engine written in VB.NET 2010

- by neil chen

When I'm reading SICP (Structure and Interpretation of Computer Programs) recently, I'm very interested in the concept of an "Nondeterministic Algorithm". According to wikipedia: In computer science, a nondeterministic algorithm is an algorithm with one or more choice points where multiple different continuations are possible, without any specification of which one will be taken. For example, here is an puzzle came from the SICP: Baker, Cooper, Fletcher, Miller, and Smith live on different floors of an apartment housethat contains only five floors. Baker does not live on the top floor. Cooper does not live onthe bottom floor. Fletcher does not live on either the top or the bottom floor. Miller lives ona higher floor than does Cooper. Smith does not live on a floor adjacent to Fletcher's.Fletcher does not live on a floor adjacent to Cooper's. Where does everyone live? After reading this I decided to build a simple nondeterministic calculation engine with .NET. The rough idea is that we can use an iterator to track each set of possible values of the parameters, and then we implement some logic inside the engine to automate the statemachine, so that we can try one combination of the values, then test it, and then move to the next. We also used a backtracking algorithm to go back when we are running out of choices at some point. Following is the core code of the engine itself: Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/--Public Class NonDeterministicEngine Private _paramDict As New List(Of Tuple(Of String, IEnumerator)) 'Private _predicateDict As New List(Of Tuple(Of Func(Of Object, Boolean), IEnumerable(Of String))) Private _predicateDict As New List(Of Tuple(Of Object, IList(Of String))) Public Sub AddParam(ByVal name As String, ByVal values As IEnumerable) _paramDict.Add(New Tuple(Of String, IEnumerator)(name, values.GetEnumerator())) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(1, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(2, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Object, Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(3, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Object, Object, Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(4, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Object, Object, Object, Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(5, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Object, Object, Object, Object, Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(6, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Object, Object, Object, Object, Object, Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(7, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Object, Object, Object, Object, Object, Object, Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(8, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Sub CheckParamCount(ByVal count As Integer, ByVal paramNames As IList(Of String)) If paramNames.Count <> count Then Throw New Exception("Parameter count does not match.") End If End Sub Public Property IterationOver As Boolean Private _firstTime As Boolean = True Public ReadOnly Property Current As Dictionary(Of String, Object) Get If IterationOver Then Return Nothing Else Dim _nextResult = New Dictionary(Of String, Object) For Each item In _paramDict Dim iter = item.Item2 _nextResult.Add(item.Item1, iter.Current) Next Return _nextResult End If End Get End Property Function MoveNext() As Boolean If IterationOver Then Return False End If If _firstTime Then For Each item In _paramDict Dim iter = item.Item2 iter.MoveNext() Next _firstTime = False Return True Else Dim canMoveNext = False Dim iterIndex = _paramDict.Count - 1 canMoveNext = _paramDict(iterIndex).Item2.MoveNext If canMoveNext Then Return True End If Do While Not canMoveNext iterIndex = iterIndex - 1 If iterIndex = -1 Then Return False IterationOver = True End If canMoveNext = _paramDict(iterIndex).Item2.MoveNext If canMoveNext Then For i = iterIndex + 1 To _paramDict.Count - 1 Dim iter = _paramDict(i).Item2 iter.Reset() iter.MoveNext() Next Return True End If Loop End If End Function Function GetNextResult() As Dictionary(Of String, Object) While MoveNext() Dim result = Current If Satisfy(result) Then Return result End If End While Return Nothing End Function Function Satisfy(ByVal result As Dictionary(Of String, Object)) As Boolean For Each item In _predicateDict Dim pred = item.Item1 Select Case item.Item2.Count Case 1 Dim p1 = DirectCast(pred, Func(Of Object, Boolean)) Dim v1 = result(item.Item2(0)) If Not p1(v1) Then Return False End If Case 2 Dim p2 = DirectCast(pred, Func(Of Object, Object, Boolean)) Dim v1 = result(item.Item2(0)) Dim v2 = result(item.Item2(1)) If Not p2(v1, v2) Then Return False End If Case 3 Dim p3 = DirectCast(pred, Func(Of Object, Object, Object, Boolean)) Dim v1 = result(item.Item2(0)) Dim v2 = result(item.Item2(1)) Dim v3 = result(item.Item2(2)) If Not p3(v1, v2, v3) Then Return False End If Case 4 Dim p4 = DirectCast(pred, Func(Of Object, Object, Object, Object, Boolean)) Dim v1 = result(item.Item2(0)) Dim v2 = result(item.Item2(1)) Dim v3 = result(item.Item2(2)) Dim v4 = result(item.Item2(3)) If Not p4(v1, v2, v3, v4) Then Return False End If Case 5 Dim p5 = DirectCast(pred, Func(Of Object, Object, Object, Object, Object, Boolean)) Dim v1 = result(item.Item2(0)) Dim v2 = result(item.Item2(1)) Dim v3 = result(item.Item2(2)) Dim v4 = result(item.Item2(3)) Dim v5 = result(item.Item2(4)) If Not p5(v1, v2, v3, v4, v5) Then Return False End If Case 6 Dim p6 = DirectCast(pred, Func(Of Object, Object, Object, Object, Object, Object, Boolean)) Dim v1 = result(item.Item2(0)) Dim v2 = result(item.Item2(1)) Dim v3 = result(item.Item2(2)) Dim v4 = result(item.Item2(3)) Dim v5 = result(item.Item2(4)) Dim v6 = result(item.Item2(5)) If Not p6(v1, v2, v3, v4, v5, v6) Then Return False End If Case 7 Dim p7 = DirectCast(pred, Func(Of Object, Object, Object, Object, Object, Object, Object, Boolean)) Dim v1 = result(item.Item2(0)) Dim v2 = result(item.Item2(1)) Dim v3 = result(item.Item2(2)) Dim v4 = result(item.Item2(3)) Dim v5 = result(item.Item2(4)) Dim v6 = result(item.Item2(5)) Dim v7 = result(item.Item2(6)) If Not p7(v1, v2, v3, v4, v5, v6, v7) Then Return False End If Case 8 Dim p8 = DirectCast(pred, Func(Of Object, Object, Object, Object, Object, Object, Object, Object, Boolean)) Dim v1 = result(item.Item2(0)) Dim v2 = result(item.Item2(1)) Dim v3 = result(item.Item2(2)) Dim v4 = result(item.Item2(3)) Dim v5 = result(item.Item2(4)) Dim v6 = result(item.Item2(5)) Dim v7 = result(item.Item2(6)) Dim v8 = result(item.Item2(7)) If Not p8(v1, v2, v3, v4, v5, v6, v7, v8) Then Return False End If Case Else Throw New NotSupportedException End Select Next Return True End FunctionEnd Class And now we can use the engine to solve the problem we mentioned above: Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/--Sub Test2() Dim engine = New NonDeterministicEngine() engine.AddParam("baker", {1, 2, 3, 4, 5}) engine.AddParam("cooper", {1, 2, 3, 4, 5}) engine.AddParam("fletcher", {1, 2, 3, 4, 5}) engine.AddParam("miller", {1, 2, 3, 4, 5}) engine.AddParam("smith", {1, 2, 3, 4, 5}) engine.AddRequire(Function(baker) As Boolean Return baker <> 5 End Function, {"baker"}) engine.AddRequire(Function(cooper) As Boolean Return cooper <> 1 End Function, {"cooper"}) engine.AddRequire(Function(fletcher) As Boolean Return fletcher <> 1 And fletcher <> 5 End Function, {"fletcher"}) engine.AddRequire(Function(miller, cooper) As Boolean 'Return miller = cooper + 1 Return miller > cooper End Function, {"miller", "cooper"}) engine.AddRequire(Function(smith, fletcher) As Boolean Return smith <> fletcher + 1 And smith <> fletcher - 1 End Function, {"smith", "fletcher"}) engine.AddRequire(Function(fletcher, cooper) As Boolean Return fletcher <> cooper + 1 And fletcher <> cooper - 1 End Function, {"fletcher", "cooper"}) engine.AddRequire(Function(a, b, c, d, e) As Boolean Return a <> b And a <> c And a <> d And a <> e And b <> c And b <> d And b <> e And c <> d And c <> e And d <> e End Function, {"baker", "cooper", "fletcher", "miller", "smith"}) Dim result = engine.GetNextResult() While Not result Is Nothing Console.WriteLine(String.Format("baker: {0}, cooper: {1}, fletcher: {2}, miller: {3}, smith: {4}", result("baker"), result("cooper"), result("fletcher"), result("miller"), result("smith"))) result = engine.GetNextResult() End While Console.WriteLine("Calculation ended.")End Sub Also, this engine can solve the classic 8 queens puzzle and find out all 92 results for me. Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/--Sub Test3() ' The 8-Queens problem. Dim engine = New NonDeterministicEngine() ' Let's assume that a - h represents the queens in row 1 to 8, then we just need to find out the column number for each of them. engine.AddParam("a", {1, 2, 3, 4, 5, 6, 7, 8}) engine.AddParam("b", {1, 2, 3, 4, 5, 6, 7, 8}) engine.AddParam("c", {1, 2, 3, 4, 5, 6, 7, 8}) engine.AddParam("d", {1, 2, 3, 4, 5, 6, 7, 8}) engine.AddParam("e", {1, 2, 3, 4, 5, 6, 7, 8}) engine.AddParam("f", {1, 2, 3, 4, 5, 6, 7, 8}) engine.AddParam("g", {1, 2, 3, 4, 5, 6, 7, 8}) engine.AddParam("h", {1, 2, 3, 4, 5, 6, 7, 8}) Dim NotInTheSameDiagonalLine = Function(cols As IList) As Boolean For i = 0 To cols.Count - 2 For j = i + 1 To cols.Count - 1 If j - i = Math.Abs(cols(j) - cols(i)) Then Return False End If Next Next Return True End Function engine.AddRequire(Function(a, b, c, d, e, f, g, h) As Boolean Return a <> b AndAlso a <> c AndAlso a <> d AndAlso a <> e AndAlso a <> f AndAlso a <> g AndAlso a <> h AndAlso b <> c AndAlso b <> d AndAlso b <> e AndAlso b <> f AndAlso b <> g AndAlso b <> h AndAlso c <> d AndAlso c <> e AndAlso c <> f AndAlso c <> g AndAlso c <> h AndAlso d <> e AndAlso d <> f AndAlso d <> g AndAlso d <> h AndAlso e <> f AndAlso e <> g AndAlso e <> h AndAlso f <> g AndAlso f <> h AndAlso g <> h AndAlso NotInTheSameDiagonalLine({a, b, c, d, e, f, g, h}) End Function, {"a", "b", "c", "d", "e", "f", "g", "h"}) Dim result = engine.GetNextResult() While Not result Is Nothing Console.WriteLine("(1,{0}), (2,{1}), (3,{2}), (4,{3}), (5,{4}), (6,{5}), (7,{6}), (8,{7})", result("a"), result("b"), result("c"), result("d"), result("e"), result("f"), result("g"), result("h")) result = engine.GetNextResult() End While Console.WriteLine("Calculation ended.")End Sub (Chinese version of the post: http://www.cnblogs.com/RChen/archive/2010/05/17/1737587.html) Cheers,

Read the article

Anti-Forgery Request Recipes For ASP.NET MVC And AJAX

- by Dixin

Background To secure websites from cross-site request forgery (CSRF, or XSRF) attack, ASP.NET MVC provides an excellent mechanism: The server prints tokens to cookie and inside the form; When the form is submitted to server, token in cookie and token inside the form are sent in the HTTP request; Server validates the tokens. To print tokens to browser, just invoke HtmlHelper.AntiForgeryToken():<% using (Html.BeginForm()) { %> <%: this.Html.AntiForgeryToken(Constants.AntiForgeryTokenSalt)%> <%-- Other fields. --%> <input type="submit" value="Submit" /> <% } %> This invocation generates a token then writes inside the form:<form action="..." method="post"> <input name="__RequestVerificationToken" type="hidden" value="J56khgCvbE3bVcsCSZkNVuH9Cclm9SSIT/ywruFsXEgmV8CL2eW5C/gGsQUf/YuP" />  <input type="submit" value="Submit" /> </form> and also writes into the cookie: __RequestVerificationToken_Lw__= J56khgCvbE3bVcsCSZkNVuH9Cclm9SSIT/ywruFsXEgmV8CL2eW5C/gGsQUf/YuP When the above form is submitted, they are both sent to server. In the server side, [ValidateAntiForgeryToken] attribute is used to specify the controllers or actions to validate them:[HttpPost] [ValidateAntiForgeryToken(Salt = Constants.AntiForgeryTokenSalt)] public ActionResult Action(/* ... */) { // ... } This is very productive for form scenarios. But recently, when resolving security vulnerabilities for Web products, some problems are encountered. Specify validation on controller (not on each action) The server side problem is, It is expected to declare [ValidateAntiForgeryToken] on controller, but actually it has be to declared on each POST actions. Because POST actions are usually much more then controllers, the work would be a little crazy. Problem Usually a controller contains actions for HTTP GET and actions for HTTP POST requests, and usually validations are expected for HTTP POST requests. So, if the [ValidateAntiForgeryToken] is declared on the controller, the HTTP GET requests become invalid:[ValidateAntiForgeryToken(Salt = Constants.AntiForgeryTokenSalt)] public class SomeController : Controller // One [ValidateAntiForgeryToken] attribute. { [HttpGet] public ActionResult Index() // Index() cannot work. { // ... } [HttpPost] public ActionResult PostAction1(/* ... */) { // ... } [HttpPost] public ActionResult PostAction2(/* ... */) { // ... } // ... } If browser sends an HTTP GET request by clicking a link: http://Site/Some/Index, validation definitely fails, because no token is provided. So the result is, [ValidateAntiForgeryToken] attribute must be distributed to each POST action:public class SomeController : Controller // Many [ValidateAntiForgeryToken] attributes. { [HttpGet] public ActionResult Index() // Works. { // ... } [HttpPost] [ValidateAntiForgeryToken(Salt = Constants.AntiForgeryTokenSalt)] public ActionResult PostAction1(/* ... */) { // ... } [HttpPost] [ValidateAntiForgeryToken(Salt = Constants.AntiForgeryTokenSalt)] public ActionResult PostAction2(/* ... */) { // ... } // ... } This is a little bit crazy, because one application can have a lot of POST actions. Solution To avoid a large number of [ValidateAntiForgeryToken] attributes (one for each POST action), the following ValidateAntiForgeryTokenWrapperAttribute wrapper class can be helpful, where HTTP verbs can be specified:[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)] public class ValidateAntiForgeryTokenWrapperAttribute : FilterAttribute, IAuthorizationFilter { private readonly ValidateAntiForgeryTokenAttribute _validator; private readonly AcceptVerbsAttribute _verbs; public ValidateAntiForgeryTokenWrapperAttribute(HttpVerbs verbs) : this(verbs, null) { } public ValidateAntiForgeryTokenWrapperAttribute(HttpVerbs verbs, string salt) { this._verbs = new AcceptVerbsAttribute(verbs); this._validator = new ValidateAntiForgeryTokenAttribute() { Salt = salt }; } public void OnAuthorization(AuthorizationContext filterContext) { string httpMethodOverride = filterContext.HttpContext.Request.GetHttpMethodOverride(); if (this._verbs.Verbs.Contains(httpMethodOverride, StringComparer.OrdinalIgnoreCase)) { this._validator.OnAuthorization(filterContext); } } } When this attribute is declared on controller, only HTTP requests with the specified verbs are validated:[ValidateAntiForgeryTokenWrapper(HttpVerbs.Post, Constants.AntiForgeryTokenSalt)] public class SomeController : Controller { // GET actions are not affected. // Only HTTP POST requests are validated. } Now one single attribute on controller turns on validation for all POST actions. Maybe it would be nice if HTTP verbs can be specified on the built-in [ValidateAntiForgeryToken] attribute, which is easy to implemented. Specify Non-constant salt in runtime By default, the salt should be a compile time constant, so it can be used for the [ValidateAntiForgeryToken] or [ValidateAntiForgeryTokenWrapper] attribute. Problem One Web product might be sold to many clients. If a constant salt is evaluated in compile time, after the product is built and deployed to many clients, they all have the same salt. Of course, clients do not like this. Even some clients might want to specify a custom salt in configuration. In these scenarios, salt is required to be a runtime value. Solution In the above [ValidateAntiForgeryToken] and [ValidateAntiForgeryTokenWrapper] attribute, the salt is passed through constructor. So one solution is to remove this parameter:public class ValidateAntiForgeryTokenWrapperAttribute : FilterAttribute, IAuthorizationFilter { public ValidateAntiForgeryTokenWrapperAttribute(HttpVerbs verbs) { this._verbs = new AcceptVerbsAttribute(verbs); this._validator = new ValidateAntiForgeryTokenAttribute() { Salt = AntiForgeryToken.Value }; } // Other members. } But here the injected dependency becomes a hard dependency. So the other solution is moving validation code into controller to work around the limitation of attributes:public abstract class AntiForgeryControllerBase : Controller { private readonly ValidateAntiForgeryTokenAttribute _validator; private readonly AcceptVerbsAttribute _verbs; protected AntiForgeryControllerBase(HttpVerbs verbs, string salt) { this._verbs = new AcceptVerbsAttribute(verbs); this._validator = new ValidateAntiForgeryTokenAttribute() { Salt = salt }; } protected override void OnAuthorization(AuthorizationContext filterContext) { base.OnAuthorization(filterContext); string httpMethodOverride = filterContext.HttpContext.Request.GetHttpMethodOverride(); if (this._verbs.Verbs.Contains(httpMethodOverride, StringComparer.OrdinalIgnoreCase)) { this._validator.OnAuthorization(filterContext); } } } Then make controller classes inheriting from this AntiForgeryControllerBase class. Now the salt is no long required to be a compile time constant. Submit token via AJAX For browser side, once server side turns on anti-forgery validation for HTTP POST, all AJAX POST requests will fail by default. Problem In AJAX scenarios, the HTTP POST request is not sent by form. Take jQuery as an example:$.post(url, { productName: "Tofu", categoryId: 1 // Token is not posted. }, callback); This kind of AJAX POST requests will always be invalid, because server side code cannot see the token in the posted data. Solution Basically, the tokens must be printed to browser then sent back to server. So first of all, HtmlHelper.AntiForgeryToken() need to be called somewhere. Now the browser has token in both HTML and cookie. Then jQuery must find the printed token in the HTML, and append token to the data before sending:$.post(url, { productName: "Tofu", categoryId: 1, __RequestVerificationToken: getToken() // Token is posted. }, callback); To be reusable, this can be encapsulated into a tiny jQuery plugin:/// <reference path="jquery-1.4.2.js" /> (function ($) { $.getAntiForgeryToken = function (tokenWindow, appPath) { // HtmlHelper.AntiForgeryToken() must be invoked to print the token. tokenWindow = tokenWindow && typeof tokenWindow === typeof window ? tokenWindow : window; appPath = appPath && typeof appPath === "string" ? "_" + appPath.toString() : ""; // The name attribute is either __RequestVerificationToken, // or __RequestVerificationToken_{appPath}. tokenName = "__RequestVerificationToken" + appPath; // Finds the <input type="hidden" name={tokenName} value="..." /> from the specified. // var inputElements = $("input[type='hidden'][name='__RequestVerificationToken" + appPath + "']"); var inputElements = tokenWindow.document.getElementsByTagName("input"); for (var i = 0; i < inputElements.length; i++) { var inputElement = inputElements[i]; if (inputElement.type === "hidden" && inputElement.name === tokenName) { return { name: tokenName, value: inputElement.value }; } } return null; }; $.appendAntiForgeryToken = function (data, token) { // Converts data if not already a string. if (data && typeof data !== "string") { data = $.param(data); } // Gets token from current window by default. token = token ? token : $.getAntiForgeryToken(); // $.getAntiForgeryToken(window). data = data ? data + "&" : ""; // If token exists, appends {token.name}={token.value} to data. return token ? data + encodeURIComponent(token.name) + "=" + encodeURIComponent(token.value) : data; }; // Wraps $.post(url, data, callback, type). $.postAntiForgery = function (url, data, callback, type) { return $.post(url, $.appendAntiForgeryToken(data), callback, type); }; // Wraps $.ajax(settings). $.ajaxAntiForgery = function (settings) { settings.data = $.appendAntiForgeryToken(settings.data); return $.ajax(settings); }; })(jQuery); In most of the scenarios, it is Ok to just replace $.post() invocation with $.postAntiForgery(), and replace $.ajax() with $.ajaxAntiForgery():$.postAntiForgery(url, { productName: "Tofu", categoryId: 1 }, callback); // Token is posted. There might be some scenarios of custom token, where $.appendAntiForgeryToken() is useful:data = $.appendAntiForgeryToken(data, token); // Token is already in data. No need to invoke $.postAntiForgery(). $.post(url, data, callback); And there are scenarios that the token is not in the current window. For example, an HTTP POST request can be sent by an iframe, while the token is in the parent window. Here, token's container window can be specified for $.getAntiForgeryToken():data = $.appendAntiForgeryToken(data, $.getAntiForgeryToken(window.parent)); // Token is already in data. No need to invoke $.postAntiForgery(). $.post(url, data, callback); If you have better solution, please do tell me.

Read the article

Passing multiple simple POST Values to ASP.NET Web API

- by Rick Strahl

A few weeks backs I posted a blog post about what does and doesn't work with ASP.NET Web API when it comes to POSTing data to a Web API controller. One of the features that doesn't work out of the box - somewhat unexpectedly - is the ability to map POST form variables to simple parameters of a Web API method. For example imagine you have this form and you want to post this data to a Web API end point like this via AJAX: <form> Name: <input type="name" name="name" value="Rick" /> Value: <input type="value" name="value" value="12" /> Entered: <input type="entered" name="entered" value="12/01/2011" /> <input type="button" id="btnSend" value="Send" /> </form> <script type="text/javascript"> $("#btnSend").click( function() { $.post("samples/PostMultipleSimpleValues?action=kazam", $("form").serialize(), function (result) { alert(result); }); }); </script> or you might do this more explicitly by creating a simple client map and specifying the POST values directly by hand:$.post("samples/PostMultipleSimpleValues?action=kazam", { name: "Rick", value: 1, entered: "12/01/2012" }, $("form").serialize(), function (result) { alert(result); }); On the wire this generates a simple POST request with Url Encoded values in the content:POST /AspNetWebApi/samples/PostMultipleSimpleValues?action=kazam HTTP/1.1 Host: localhost User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:15.0) Gecko/20100101 Firefox/15.0.1 Accept: application/json Connection: keep-alive Content-Type: application/x-www-form-urlencoded; charset=UTF-8 X-Requested-With: XMLHttpRequest Referer: http://localhost/AspNetWebApi/FormPostTest.html Content-Length: 41 Pragma: no-cache Cache-Control: no-cachename=Rick&value=12&entered=12%2F10%2F2011 Seems simple enough, right? We are basically posting 3 form variables and 1 query string value to the server. Unfortunately Web API can't handle request out of the box. If I create a method like this:[HttpPost] public string PostMultipleSimpleValues(string name, int value, DateTime entered, string action = null) { return string.Format("Name: {0}, Value: {1}, Date: {2}, Action: {3}", name, value, entered, action); }You'll find that you get an HTTP 404 error and { "Message": "No HTTP resource was found that matches the request URI…"} Yes, it's possible to pass multiple POST parameters of course, but Web API expects you to use Model Binding for this - mapping the post parameters to a strongly typed .NET object, not to single parameters. Alternately you can also accept a FormDataCollection parameter on your API method to get a name value collection of all POSTed values. If you're using JSON only, using the dynamic JObject/JValue objects might also work. ModelBinding is fine in many use cases, but can quickly become overkill if you only need to pass a couple of simple parameters to many methods. Especially in applications with many, many AJAX callbacks the 'parameter mapping type' per method signature can lead to serious class pollution in a project very quickly. Simple POST variables are also commonly used in AJAX applications to pass data to the server, even in many complex public APIs. So this is not an uncommon use case, and - maybe more so a behavior that I would have expected Web API to support natively. The question "Why aren't my POST parameters mapping to Web API method parameters" is already a frequent one… So this is something that I think is fairly important, but unfortunately missing in the base Web API installation. Creating a Custom Parameter Binder Luckily Web API is greatly extensible and there's a way to create a custom Parameter Binding to provide this functionality! Although this solution took me a long while to find and then only with the help of some folks Microsoft (thanks Hong Mei!!!), it's not difficult to hook up in your own projects. It requires one small class and a GlobalConfiguration hookup. Web API parameter bindings allow you to intercept processing of individual parameters - they deal with mapping parameters to the signature as well as converting the parameters to the actual values that are returned. Here's the implementation of the SimplePostVariableParameterBinding class:public class SimplePostVariableParameterBinding : HttpParameterBinding { private const string MultipleBodyParameters = "MultipleBodyParameters"; public SimplePostVariableParameterBinding(HttpParameterDescriptor descriptor) : base(descriptor) { } /// <summary> /// Check for simple binding parameters in POST data. Bind POST /// data as well as query string data /// </summary> public override Task ExecuteBindingAsync(ModelMetadataProvider metadataProvider, HttpActionContext actionContext, CancellationToken cancellationToken) { // Body can only be read once, so read and cache it NameValueCollection col = TryReadBody(actionContext.Request); string stringValue = null; if (col != null) stringValue = col[Descriptor.ParameterName]; // try reading query string if we have no POST/PUT match if (stringValue == null) { var query = actionContext.Request.GetQueryNameValuePairs(); if (query != null) { var matches = query.Where(kv => kv.Key.ToLower() == Descriptor.ParameterName.ToLower()); if (matches.Count() > 0) stringValue = matches.First().Value; } } object value = StringToType(stringValue); // Set the binding result here SetValue(actionContext, value); // now, we can return a completed task with no result TaskCompletionSource<AsyncVoid> tcs = new TaskCompletionSource<AsyncVoid>(); tcs.SetResult(default(AsyncVoid)); return tcs.Task; } private object StringToType(string stringValue) { object value = null; if (stringValue == null) value = null; else if (Descriptor.ParameterType == typeof(string)) value = stringValue; else if (Descriptor.ParameterType == typeof(int)) value = int.Parse(stringValue, CultureInfo.CurrentCulture); else if (Descriptor.ParameterType == typeof(Int32)) value = Int32.Parse(stringValue, CultureInfo.CurrentCulture); else if (Descriptor.ParameterType == typeof(Int64)) value = Int64.Parse(stringValue, CultureInfo.CurrentCulture); else if (Descriptor.ParameterType == typeof(decimal)) value = decimal.Parse(stringValue, CultureInfo.CurrentCulture); else if (Descriptor.ParameterType == typeof(double)) value = double.Parse(stringValue, CultureInfo.CurrentCulture); else if (Descriptor.ParameterType == typeof(DateTime)) value = DateTime.Parse(stringValue, CultureInfo.CurrentCulture); else if (Descriptor.ParameterType == typeof(bool)) { value = false; if (stringValue == "true" || stringValue == "on" || stringValue == "1") value = true; } else value = stringValue; return value; } /// <summary> /// Read and cache the request body /// </summary> /// <param name="request"></param> /// <returns></returns> private NameValueCollection TryReadBody(HttpRequestMessage request) { object result = null; // try to read out of cache first if (!request.Properties.TryGetValue(MultipleBodyParameters, out result)) { // parsing the string like firstname=Hongmei&lastname=Ge result = request.Content.ReadAsFormDataAsync().Result; request.Properties.Add(MultipleBodyParameters, result); } return result as NameValueCollection; } private struct AsyncVoid { } } The ExecuteBindingAsync method is fired for each parameter that is mapped and sent for conversion. This custom binding is fired only if the incoming parameter is a simple type (that gets defined later when I hook up the binding), so this binding never fires on complex types or if the first type is not a simple type. For the first parameter of a request the Binding first reads the request body into a NameValueCollection and caches that in the request.Properties collection. The request body can only be read once, so the first parameter request reads it and then caches it. Subsequent parameters then use the cached POST value collection. Once the form collection is available the value of the parameter is read, and the value is translated into the target type requested by the Descriptor. SetValue writes out the value to be mapped. Once you have the ParameterBinding in place, the binding has to be assigned. This is done along with all other Web API configuration tasks at application startup in global.asax's Application_Start:GlobalConfiguration.Configuration.ParameterBindingRules .Insert(0, (HttpParameterDescriptor descriptor) => { var supportedMethods = descriptor.ActionDescriptor.SupportedHttpMethods; // Only apply this binder on POST and PUT operations if (supportedMethods.Contains(HttpMethod.Post) || supportedMethods.Contains(HttpMethod.Put)) { var supportedTypes = new Type[] { typeof(string), typeof(int), typeof(decimal), typeof(double), typeof(bool), typeof(DateTime) }; if (supportedTypes.Where(typ => typ == descriptor.ParameterType).Count() > 0) return new SimplePostVariableParameterBinding(descriptor); } // let the default bindings do their work return null; }); The ParameterBindingRules.Insert method takes a delegate that checks which type of requests it should handle. The logic here checks whether the request is POST or PUT and whether the parameter type is a simple type that is supported. Web API calls this delegate once for each method signature it tries to map and the delegate returns null to indicate it's not handling this parameter, or it returns a new parameter binding instance - in this case the SimplePostVariableParameterBinding. Once the parameter binding and this hook up code is in place, you can now pass simple POST values to methods with simple parameters. The examples I showed above should now work in addition to the standard bindings. Summary Clearly this is not easy to discover. I spent quite a bit of time digging through the Web API source trying to figure this out on my own without much luck. It took Hong Mei at Micrsoft to provide a base example as I asked around so I can't take credit for this solution :-). But once you know where to look, Web API is brilliantly extensible to make it relatively easy to customize the parameter behavior. I'm very stoked that this got resolved - in the last two months I've had two customers with projects that decided not to use Web API in AJAX heavy SPA applications because this POST variable mapping wasn't available. This might actually change their mind to still switch back and take advantage of the many great features in Web API. I too frequently use plain POST variables for communicating with server AJAX handlers and while I could have worked around this (with untyped JObject or the Form collection mostly), having proper POST to parameter mapping makes things much easier. I said this in my last post on POST data and say it again here: I think POST to method parameter mapping should have been shipped in the box with Web API, because without knowing about this limitation the expectation is that simple POST variables map to parameters just like query string values do. I hope Microsoft considers including this type of functionality natively in the next version of Web API natively or at least as a built-in HttpParameterBinding that can be just added. This is especially true, since this binding doesn't affect existing bindings. Resources SimplePostVariableParameterBinding Source on GitHub Global.asax hookup source Mapping URL Encoded Post Values in ASP.NET Web API© Rick Strahl, West Wind Technologies, 2005-2012Posted in Web Api AJAX Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

Read the article

TOTD #166: Using NoSQL database in your Java EE 6 Applications on GlassFish - MongoDB for now!

- by arungupta

The Java EE 6 platform includes Java Persistence API to work with RDBMS. The JPA specification defines a comprehensive API that includes, but not restricted to, how a database table can be mapped to a POJO and vice versa, provides mechanisms how a PersistenceContext can be injected in a @Stateless bean and then be used for performing different operations on the database table and write typesafe queries. There are several well known advantages of RDBMS but the NoSQL movement has gained traction over past couple of years. The NoSQL databases are not intended to be a replacement for the mainstream RDBMS. As Philosophy of NoSQL explains, NoSQL database was designed for casual use where all the features typically provided by an RDBMS are not required. The name "NoSQL" is more of a category of databases that is more known for what it is not rather than what it is. The basic principles of NoSQL database are: No need to have a pre-defined schema and that makes them a schema-less database. Addition of new properties to existing objects is easy and does not require ALTER TABLE. The unstructured data gives flexibility to change the format of data any time without downtime or reduced service levels. Also there are no joins happening on the server because there is no structure and thus no relation between them. Scalability and performance is more important than the entire set of functionality typically provided by an RDBMS. This set of databases provide eventual consistency and/or transactions restricted to single items but more focus on CRUD. Not be restricted to SQL to access the information stored in the backing database. Designed to scale-out (horizontal) instead of scale-up (vertical). This is important knowing that databases, and everything else as well, is moving into the cloud. RBDMS can scale-out using sharding but requires complex management and not for the faint of heart. Unlike RBDMS which require a separate caching tier, most of the NoSQL databases comes with integrated caching. Designed for less management and simpler data models lead to lower administration as well. There are primarily three types of NoSQL databases: Key-Value stores (e.g. Cassandra and Riak) Document databases (MongoDB or CouchDB) Graph databases (Neo4J) You may think NoSQL is panacea but as I mentioned above they are not meant to replace the mainstream databases and here is why: RDBMS have been around for many years, very stable, and functionally rich. This is something CIOs and CTOs can bet their money on without much worry. There is a reason 98% of Fortune 100 companies run Oracle :-) NoSQL is cutting edge, brings excitement to developers, but enterprises are cautious about them. Commercial databases like Oracle are well supported by the backing enterprises in terms of providing support resources on a global scale. There is a full ecosystem built around these commercial databases providing training, performance tuning, architecture guidance, and everything else. NoSQL is fairly new and typically backed by a single company not able to meet the scale of these big enterprises. NoSQL databases are good for CRUDing operations but business intelligence is extremely important for enterprises to stay competitive. RDBMS provide extensive tooling to generate this data but that was not the original intention of NoSQL databases and is lacking in that area. Generating any meaningful information other than CRUDing require extensive programming. Not suited for complex transactions such as banking systems or other highly transactional applications requiring 2-phase commit. SQL cannot be used with NoSQL databases and writing simple queries can be involving. Enough talking, lets take a look at some code. This blog has published multiple blogs on how to access a RDBMS using JPA in a Java EE 6 application. This Tip Of The Day (TOTD) will show you can use MongoDB (a document-oriented database) with a typical 3-tier Java EE 6 application. Lets get started! The complete source code of this project can be downloaded here. Download MongoDB for your platform from here (1.8.2 as of this writing) and start the server as: arun@ArunUbuntu:~/tools/mongodb-linux-x86_64-1.8.2/bin$./mongod./mongod --help for help and startup optionsSun Jun 26 20:41:11 [initandlisten] MongoDB starting : pid=11210port=27017 dbpath=/data/db/ 64-bit Sun Jun 26 20:41:11 [initandlisten] db version v1.8.2, pdfile version4.5Sun Jun 26 20:41:11 [initandlisten] git version:433bbaa14aaba6860da15bd4de8edf600f56501bSun Jun 26 20:41:11 [initandlisten] build sys info: Linuxbs-linux64.10gen.cc 2.6.21.7-2.ec2.v1.2.fc8xen #1 SMP Fri Nov 2017:48:28 EST 2009 x86_64 BOOST_LIB_VERSION=1_41Sun Jun 26 20:41:11 [initandlisten] waiting for connections on port 27017Sun Jun 26 20:41:11 [websvr] web admin interface listening on port 28017 The default directory for the database is /data/db and needs to be created as: sudo mkdir -p /data/db/sudo chown `id -u` /data/db You can specify a different directory using "--dbpath" option. Refer to Quickstart for your specific platform. Using NetBeans, create a Java EE 6 project and make sure to enable CDI and add JavaServer Faces framework. Download MongoDB Java Driver (2.6.3 of this writing) and add it to the project library by selecting "Properties", "LIbraries", "Add Library...", creating a new library by specifying the location of the JAR file, and adding the library to the created project. Edit the generated "index.xhtml" such that it looks like: <h1>Add a new movie</h1><h:form> Name: <h:inputText value="#{movie.name}" size="20"/><br/> Year: <h:inputText value="#{movie.year}" size="6"/><br/> Language: <h:inputText value="#{movie.language}" size="20"/><br/> <h:commandButton actionListener="#{movieSessionBean.createMovie}" action="show" title="Add" value="submit"/></h:form> This page has a simple HTML form with three text boxes and a submit button. The text boxes take name, year, and language of a movie and the submit button invokes the "createMovie" method of "movieSessionBean" and then render "show.xhtml". Create "show.xhtml" ("New" -> "Other..." -> "Other" -> "XHTML File") such that it looks like: <head> <title><h1>List of movies</h1></title> </head> <body> <h:form> <h:dataTable value="#{movieSessionBean.movies}" var="m" > <h:column><f:facet name="header">Name</f:facet>#{m.name}</h:column> <h:column><f:facet name="header">Year</f:facet>#{m.year}</h:column> <h:column><f:facet name="header">Language</f:facet>#{m.language}</h:column> </h:dataTable> </h:form> This page shows the name, year, and language of all movies stored in the database so far. The list of movies is returned by "movieSessionBean.movies" property. Now create the "Movie" class such that it looks like: import com.mongodb.BasicDBObject;import com.mongodb.BasicDBObject;import com.mongodb.DBObject;import javax.enterprise.inject.Model;import javax.validation.constraints.Size;/** * @author arun */@Modelpublic class Movie { @Size(min=1, max=20) private String name; @Size(min=1, max=20) private String language; private int year; // getters and setters for "name", "year", "language" public BasicDBObject toDBObject() { BasicDBObject doc = new BasicDBObject(); doc.put("name", name); doc.put("year", year); doc.put("language", language); return doc; } public static Movie fromDBObject(DBObject doc) { Movie m = new Movie(); m.name = (String)doc.get("name"); m.year = (int)doc.get("year"); m.language = (String)doc.get("language"); return m; } @Override public String toString() { return name + ", " + year + ", " + language; }} Other than the usual boilerplate code, the key methods here are "toDBObject" and "fromDBObject". These methods provide a conversion from "Movie" -> "DBObject" and vice versa. The "DBObject" is a MongoDB class that comes as part of the mongo-2.6.3.jar file and which we added to our project earlier. The complete javadoc for 2.6.3 can be seen here. Notice, this class also uses Bean Validation constraints and will be honored by the JSF layer. Finally, create "MovieSessionBean" stateless EJB with all the business logic such that it looks like: package org.glassfish.samples;import com.mongodb.BasicDBObject;import com.mongodb.DB;import com.mongodb.DBCollection;import com.mongodb.DBCursor;import com.mongodb.DBObject;import com.mongodb.Mongo;import java.net.UnknownHostException;import java.util.ArrayList;import java.util.List;import javax.annotation.PostConstruct;import javax.ejb.Stateless;import javax.inject.Inject;import javax.inject.Named;/** * @author arun */@Stateless@Namedpublic class MovieSessionBean { @Inject Movie movie; DBCollection movieColl; @PostConstruct private void initDB() throws UnknownHostException { Mongo m = new Mongo(); DB db = m.getDB("movieDB"); movieColl = db.getCollection("movies"); if (movieColl == null) { movieColl = db.createCollection("movies", null); } } public void createMovie() { BasicDBObject doc = movie.toDBObject(); movieColl.insert(doc); } public List<Movie> getMovies() { List<Movie> movies = new ArrayList(); DBCursor cur = movieColl.find(); System.out.println("getMovies: Found " + cur.size() + " movie(s)"); for (DBObject dbo : cur.toArray()) { movies.add(Movie.fromDBObject(dbo)); } return movies; }} The database is initialized in @PostConstruct. Instead of a working with a database table, NoSQL databases work with a schema-less document. The "Movie" class is the document in our case and stored in the collection "movies". The collection allows us to perform query functions on all movies. The "getMovies" method invokes "find" method on the collection which is equivalent to the SQL query "select * from movies" and then returns a List<Movie>. Also notice that there is no "persistence.xml" in the project. Right-click and run the project to see the output as: Enter some values in the text box and click on enter to see the result as: If you reached here then you've successfully used MongoDB in your Java EE 6 application, congratulations! Some food for thought and further play ... SQL to MongoDB mapping shows mapping between traditional SQL -> Mongo query language. Tutorial shows fun things you can do with MongoDB. Try the interactive online shell The cookbook provides common ways of using MongoDB In terms of this project, here are some tasks that can be tried: Encapsulate database management in a JPA persistence provider. Is it even worth it because the capabilities are going to be very different ? MongoDB uses "BSonObject" class for JSON representation, add @XmlRootElement on a POJO and how a compatible JSON representation can be generated. This will make the fromXXX and toXXX methods redundant.

Read the article

TOTD #166: Using NoSQL database in your Java EE 6 Applications on GlassFish - MongoDB for now!

- by arungupta

The Java EE 6 platform includes Java Persistence API to work with RDBMS. The JPA specification defines a comprehensive API that includes, but not restricted to, how a database table can be mapped to a POJO and vice versa, provides mechanisms how a PersistenceContext can be injected in a @Stateless bean and then be used for performing different operations on the database table and write typesafe queries. There are several well known advantages of RDBMS but the NoSQL movement has gained traction over past couple of years. The NoSQL databases are not intended to be a replacement for the mainstream RDBMS. As Philosophy of NoSQL explains, NoSQL database was designed for casual use where all the features typically provided by an RDBMS are not required. The name "NoSQL" is more of a category of databases that is more known for what it is not rather than what it is. The basic principles of NoSQL database are: No need to have a pre-defined schema and that makes them a schema-less database. Addition of new properties to existing objects is easy and does not require ALTER TABLE. The unstructured data gives flexibility to change the format of data any time without downtime or reduced service levels. Also there are no joins happening on the server because there is no structure and thus no relation between them. Scalability and performance is more important than the entire set of functionality typically provided by an RDBMS. This set of databases provide eventual consistency and/or transactions restricted to single items but more focus on CRUD. Not be restricted to SQL to access the information stored in the backing database. Designed to scale-out (horizontal) instead of scale-up (vertical). This is important knowing that databases, and everything else as well, is moving into the cloud. RBDMS can scale-out using sharding but requires complex management and not for the faint of heart. Unlike RBDMS which require a separate caching tier, most of the NoSQL databases comes with integrated caching. Designed for less management and simpler data models lead to lower administration as well. There are primarily three types of NoSQL databases: Key-Value stores (e.g. Cassandra and Riak) Document databases (MongoDB or CouchDB) Graph databases (Neo4J) You may think NoSQL is panacea but as I mentioned above they are not meant to replace the mainstream databases and here is why: RDBMS have been around for many years, very stable, and functionally rich. This is something CIOs and CTOs can bet their money on without much worry. There is a reason 98% of Fortune 100 companies run Oracle :-) NoSQL is cutting edge, brings excitement to developers, but enterprises are cautious about them. Commercial databases like Oracle are well supported by the backing enterprises in terms of providing support resources on a global scale. There is a full ecosystem built around these commercial databases providing training, performance tuning, architecture guidance, and everything else. NoSQL is fairly new and typically backed by a single company not able to meet the scale of these big enterprises. NoSQL databases are good for CRUDing operations but business intelligence is extremely important for enterprises to stay competitive. RDBMS provide extensive tooling to generate this data but that was not the original intention of NoSQL databases and is lacking in that area. Generating any meaningful information other than CRUDing require extensive programming. Not suited for complex transactions such as banking systems or other highly transactional applications requiring 2-phase commit. SQL cannot be used with NoSQL databases and writing simple queries can be involving. Enough talking, lets take a look at some code. This blog has published multiple blogs on how to access a RDBMS using JPA in a Java EE 6 application. This Tip Of The Day (TOTD) will show you can use MongoDB (a document-oriented database) with a typical 3-tier Java EE 6 application. Lets get started! The complete source code of this project can be downloaded here. Download MongoDB for your platform from here (1.8.2 as of this writing) and start the server as: arun@ArunUbuntu:~/tools/mongodb-linux-x86_64-1.8.2/bin$./mongod./mongod --help for help and startup optionsSun Jun 26 20:41:11 [initandlisten] MongoDB starting : pid=11210port=27017 dbpath=/data/db/ 64-bit Sun Jun 26 20:41:11 [initandlisten] db version v1.8.2, pdfile version4.5Sun Jun 26 20:41:11 [initandlisten] git version:433bbaa14aaba6860da15bd4de8edf600f56501bSun Jun 26 20:41:11 [initandlisten] build sys info: Linuxbs-linux64.10gen.cc 2.6.21.7-2.ec2.v1.2.fc8xen #1 SMP Fri Nov 2017:48:28 EST 2009 x86_64 BOOST_LIB_VERSION=1_41Sun Jun 26 20:41:11 [initandlisten] waiting for connections on port 27017Sun Jun 26 20:41:11 [websvr] web admin interface listening on port 28017 The default directory for the database is /data/db and needs to be created as: sudo mkdir -p /data/db/sudo chown `id -u` /data/db You can specify a different directory using "--dbpath" option. Refer to Quickstart for your specific platform. Using NetBeans, create a Java EE 6 project and make sure to enable CDI and add JavaServer Faces framework. Download MongoDB Java Driver (2.6.3 of this writing) and add it to the project library by selecting "Properties", "LIbraries", "Add Library...", creating a new library by specifying the location of the JAR file, and adding the library to the created project. Edit the generated "index.xhtml" such that it looks like: <h1>Add a new movie</h1><h:form> Name: <h:inputText value="#{movie.name}" size="20"/><br/> Year: <h:inputText value="#{movie.year}" size="6"/><br/> Language: <h:inputText value="#{movie.language}" size="20"/><br/> <h:commandButton actionListener="#{movieSessionBean.createMovie}" action="show" title="Add" value="submit"/></h:form> This page has a simple HTML form with three text boxes and a submit button. The text boxes take name, year, and language of a movie and the submit button invokes the "createMovie" method of "movieSessionBean" and then render "show.xhtml". Create "show.xhtml" ("New" -> "Other..." -> "Other" -> "XHTML File") such that it looks like: <head> <title><h1>List of movies</h1></title> </head> <body> <h:form> <h:dataTable value="#{movieSessionBean.movies}" var="m" > <h:column><f:facet name="header">Name</f:facet>#{m.name}</h:column> <h:column><f:facet name="header">Year</f:facet>#{m.year}</h:column> <h:column><f:facet name="header">Language</f:facet>#{m.language}</h:column> </h:dataTable> </h:form> This page shows the name, year, and language of all movies stored in the database so far. The list of movies is returned by "movieSessionBean.movies" property. Now create the "Movie" class such that it looks like: import com.mongodb.BasicDBObject;import com.mongodb.BasicDBObject;import com.mongodb.DBObject;import javax.enterprise.inject.Model;import javax.validation.constraints.Size;/** * @author arun */@Modelpublic class Movie { @Size(min=1, max=20) private String name; @Size(min=1, max=20) private String language; private int year; // getters and setters for "name", "year", "language" public BasicDBObject toDBObject() { BasicDBObject doc = new BasicDBObject(); doc.put("name", name); doc.put("year", year); doc.put("language", language); return doc; } public static Movie fromDBObject(DBObject doc) { Movie m = new Movie(); m.name = (String)doc.get("name"); m.year = (int)doc.get("year"); m.language = (String)doc.get("language"); return m; } @Override public String toString() { return name + ", " + year + ", " + language; }} Other than the usual boilerplate code, the key methods here are "toDBObject" and "fromDBObject". These methods provide a conversion from "Movie" -> "DBObject" and vice versa. The "DBObject" is a MongoDB class that comes as part of the mongo-2.6.3.jar file and which we added to our project earlier. The complete javadoc for 2.6.3 can be seen here. Notice, this class also uses Bean Validation constraints and will be honored by the JSF layer. Finally, create "MovieSessionBean" stateless EJB with all the business logic such that it looks like: package org.glassfish.samples;import com.mongodb.BasicDBObject;import com.mongodb.DB;import com.mongodb.DBCollection;import com.mongodb.DBCursor;import com.mongodb.DBObject;import com.mongodb.Mongo;import java.net.UnknownHostException;import java.util.ArrayList;import java.util.List;import javax.annotation.PostConstruct;import javax.ejb.Stateless;import javax.inject.Inject;import javax.inject.Named;/** * @author arun */@Stateless@Namedpublic class MovieSessionBean { @Inject Movie movie; DBCollection movieColl; @PostConstruct private void initDB() throws UnknownHostException { Mongo m = new Mongo(); DB db = m.getDB("movieDB"); movieColl = db.getCollection("movies"); if (movieColl == null) { movieColl = db.createCollection("movies", null); } } public void createMovie() { BasicDBObject doc = movie.toDBObject(); movieColl.insert(doc); } public List<Movie> getMovies() { List<Movie> movies = new ArrayList(); DBCursor cur = movieColl.find(); System.out.println("getMovies: Found " + cur.size() + " movie(s)"); for (DBObject dbo : cur.toArray()) { movies.add(Movie.fromDBObject(dbo)); } return movies; }} The database is initialized in @PostConstruct. Instead of a working with a database table, NoSQL databases work with a schema-less document. The "Movie" class is the document in our case and stored in the collection "movies". The collection allows us to perform query functions on all movies. The "getMovies" method invokes "find" method on the collection which is equivalent to the SQL query "select * from movies" and then returns a List<Movie>. Also notice that there is no "persistence.xml" in the project. Right-click and run the project to see the output as: Enter some values in the text box and click on enter to see the result as: If you reached here then you've successfully used MongoDB in your Java EE 6 application, congratulations! Some food for thought and further play ... SQL to MongoDB mapping shows mapping between traditional SQL -> Mongo query language. Tutorial shows fun things you can do with MongoDB. Try the interactive online shell The cookbook provides common ways of using MongoDB In terms of this project, here are some tasks that can be tried: Encapsulate database management in a JPA persistence provider. Is it even worth it because the capabilities are going to be very different ? MongoDB uses "BSonObject" class for JSON representation, add @XmlRootElement on a POJO and how a compatible JSON representation can be generated. This will make the fromXXX and toXXX methods redundant.

Read the article

//TODO: Test this thoroughly!!!!!!

- by Edward Boyle

I just ran into an ugly sight in my code: //TODO: Test this thoroughly!!!!!! private void ... I would very much like to go back in time and ask the past me what I meant, why did I add that TODO:? …And then, smack the s%#t out of him. No matter how much testing I do of this code I will always wonder if the past me found something. Was it actually that code or was it a calling method that may bring unwanted results. The fact that I find absolutely nothing wrong with the code makes it that much more haunting. The moral of the story; when you find something wrong and need to test it thoroughly, stay up another hour testing it. The clarity in your head at that moment, on that issue, at that specific moment in time, would take hours worth of commenting to justify not finishing it now. Maybe what I meant was: // TODO: Test this thoroughly!!!!!! // All seems fine but test it just in case, not to worry. private void ... Doubt it. -I’m screwed.

Read the article

ISA forms authentication problems after installing moss sp2

- by user22215

Guys I have a problem that's flared back up after installing WSS and MOSS service pack 2. The problem centers around the users being prompted to enter credentials when interacting with office documents. This problem came up before and I was able to go into ISA server and configure a persistent cookie on the web listener. As we all know when configuring a cookie you have two options use only on private computers or use on all computers. If I select use on all computers I can't even log in to Sharepoint from the forms page however if I select use only on private computer I'm able to log in and also I don't get prompted when opening office documents. So I would like to ask has something changed with Sharepoint service pack 2 because that’s the only change that’s been made to my environment.

Read the article

CYGWin and sshd. Accepts authentication, but won't connect

- by timramich

Everything I find relating to this is the "ssh-exchange-identification:" error. This doesn't happen for me. I get two lines: Connection to localhost closed by remote host. Connection to localhost closed. ssh -v localhost spits out: OpenSSH_5.8p1, OpenSSL 0.9.8r 8 Feb 2011 debug1: Reading configuration data /etc/ssh_config debug1: Connecting to localhost [::1] port 22. debug1: Connection established. debug1: identity file /home/tim/.ssh/id_rsa type -1 debug1: identity file /home/tim/.ssh/id_rsa-cert type -1 debug1: identity file /home/tim/.ssh/id_dsa type -1 debug1: identity file /home/tim/.ssh/id_dsa-cert type -1 debug1: identity file /home/tim/.ssh/id_ecdsa type -1 debug1: identity file /home/tim/.ssh/id_ecdsa-cert type -1 debug1: Remote protocol version 2.0, remote software version OpenSSH_5.8 debug1: match: OpenSSH_5.8 pat OpenSSH* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_5.8 debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: server->client aes128-ctr hmac-md5 none debug1: kex: client->server aes128-ctr hmac-md5 none debug1: sending SSH2_MSG_KEX_ECDH_INIT debug1: expecting SSH2_MSG_KEX_ECDH_REPLY debug1: Server host key: ECDSA 64:e3:27:90:ef:48:93:21:38:ea:9b:0e:0b:07:b0:2a debug1: Host 'localhost' is known and matches the ECDSA host key. debug1: Found key in /home/tim/.ssh/known_hosts:1 debug1: ssh_ecdsa_verify: signature correct debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug1: SSH2_MSG_NEWKEYS received debug1: Roaming not allowed by server debug1: SSH2_MSG_SERVICE_REQUEST sent debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey,password,keyboard-interactive debug1: Next authentication method: publickey debug1: Trying private key: /home/tim/.ssh/id_rsa debug1: Trying private key: /home/tim/.ssh/id_dsa debug1: Trying private key: /home/tim/.ssh/id_ecdsa debug1: Next authentication method: keyboard-interactive debug1: Authentications that can continue: publickey,password,keyboard-interactive debug1: Next authentication method: password tim@localhost's password: debug1: Authentication succeeded (password). Authenticated to localhost ([::1]:22). debug1: channel 0: new [client-session] debug1: Requesting [email protected] debug1: Entering interactive session. debug1: channel 0: free: client-session, nchannels 1 Connection to localhost closed by remote host. Connection to localhost closed. Transferred: sent 2008, received 1376 bytes, in 0.0 seconds Bytes per second: sent 64774.0, received 44387.0 debug1: Exit status -1 I'm really at wit's end here because I couldn't get Windows' remote shell to even work. I'm so sick of using VNC just to get to a shell. Plus Windows' shell sucks because there is nothing like screen. Thanks

Read the article

How to find the average color of an image.

- by Edward Boyle

Years ago I was the lead developer of a large Scrapbook Web Site. One of the things I implemented was to allow shoppers to find Scrapbook papers and embellishments of like colors (“more like this color”). Below is the base algorithm I wrote to extract the color from an image. It worked out pretty well. I took the returned values and stored them in an associated table for the products. Yet another algorithm was used to SELECT near matches. This algorithm has turned out to be very handy for me. I have used it for borders and subtle outlined text overlays. I am sure you will find more creative uses for it. Enjoy… private Color GetColor(Bitmap bmp) { int r = 0; int g = 0; int b = 0; Color mColor = System.Drawing.Color.White; for (int i = 1; i < bmp.Width; i++) { for (int x = 1; x < bmp.Height; x++) { mColor = bmp.GetPixel(i, x); r += mColor.R; g += mColor.G; b += mColor.B; } } r = (r / (bmp.Height * bmp.Width)); g = (g / (bmp.Height * bmp.Width)); b = (b / (bmp.Height * bmp.Width)); return System.Drawing.Color.FromArgb(r, g, b); } You could also get the RGB values by passing in the RGB by ref private Color GetColor(ref int r, ref int g, ref int b, Bitmap bmp) but that is a bit much as you can simply get it from the return value: mReturnedColor.R; mReturnedColor.G; mReturnedColor.B;

Read the article

Uploading and Importing CSV file to SQL Server in ASP.NET WebForms

- by Vincent Maverick Durano

Few weeks ago I was working with a small internal project that involves importing CSV file to Sql Server database and thought I'd share the simple implementation that I did on the project. In this post I will demonstrate how to upload and import CSV file to SQL Server database. As some may have already know, importing CSV file to SQL Server is easy and simple but difficulties arise when the CSV file contains, many columns with different data types. Basically, the provider cannot differentiate data types between the columns or the rows, blindly it will consider them as a data type based on first few rows and leave all the data which does not match the data type. To overcome this problem, I used schema.ini file to define the data type of the CSV file and allow the provider to read that and recognize the exact data types of each column. Now what is schema.ini? Taken from the documentation: The Schema.ini is a information file, used to define the data structure and format of each column that contains data in the CSV file. If schema.ini file exists in the directory, Microsoft.Jet.OLEDB provider automatically reads it and recognizes the data type information of each column in the CSV file. Thus, the provider intelligently avoids the misinterpretation of data types before inserting the data into the database. For more information see: http://msdn.microsoft.com/en-us/library/ms709353%28VS.85%29.aspx Points to remember before creating schema.ini: 1. The schema information file, must always named as 'schema.ini'. 2. The schema.ini file must be kept in the same directory where the CSV file exists. 3. The schema.ini file must be created before reading the CSV file. 4. The first line of the schema.ini, must the name of the CSV file, followed by the properties of the CSV file, and then the properties of the each column in the CSV file. Here's an example of how the schema looked like: [Employee.csv] ColNameHeader=False Format=CSVDelimited DateTimeFormat=dd-MMM-yyyy Col1=EmployeeID Long Col2=EmployeeFirstName Text Width 100 Col3=EmployeeLastName Text Width 50 Col4=EmployeeEmailAddress Text Width 50 To get started lets's go a head and create a simple blank database. Just for the purpose of this demo I created a database called TestDB. After creating the database then lets go a head and fire up Visual Studio and then create a new WebApplication project. Under the root application create a folder called UploadedCSVFiles and then place the schema.ini on that folder. The uploaded CSV files will be stored in this folder after the user imports the file. Now add a WebForm in the project and set up the HTML mark up and add one (1) FileUpload control one(1)Button and three (3) Label controls. After that we can now proceed with the codes for uploading and importing the CSV file to SQL Server database. Here are the full code blocks below: 1: using System; 2: using System.Data; 3: using System.Data.SqlClient; 4: using System.Data.OleDb; 5: using System.IO; 6: using System.Text; 7: 8: namespace WebApplication1 9: { 10: public partial class CSVToSQLImporting : System.Web.UI.Page 11: { 12: private string GetConnectionString() 13: { 14: return System.Configuration.ConfigurationManager.ConnectionStrings["DBConnectionString"].ConnectionString; 15: } 16: private void CreateDatabaseTable(DataTable dt, string tableName) 17: { 18: 19: string sqlQuery = string.Empty; 20: string sqlDBType = string.Empty; 21: string dataType = string.Empty; 22: int maxLength = 0; 23: StringBuilder sb = new StringBuilder(); 24: 25: sb.AppendFormat(string.Format("CREATE TABLE {0} (", tableName)); 26: 27: for (int i = 0; i < dt.Columns.Count; i++) 28: { 29: dataType = dt.Columns[i].DataType.ToString(); 30: if (dataType == "System.Int32") 31: { 32: sqlDBType = "INT"; 33: } 34: else if (dataType == "System.String") 35: { 36: sqlDBType = "NVARCHAR"; 37: maxLength = dt.Columns[i].MaxLength; 38: } 39: 40: if (maxLength > 0) 41: { 42: sb.AppendFormat(string.Format(" {0} {1} ({2}), ", dt.Columns[i].ColumnName, sqlDBType, maxLength)); 43: } 44: else 45: { 46: sb.AppendFormat(string.Format(" {0} {1}, ", dt.Columns[i].ColumnName, sqlDBType)); 47: } 48: } 49: 50: sqlQuery = sb.ToString(); 51: sqlQuery = sqlQuery.Trim().TrimEnd(','); 52: sqlQuery = sqlQuery + " )"; 53: 54: using (SqlConnection sqlConn = new SqlConnection(GetConnectionString())) 55: { 56: sqlConn.Open(); 57: SqlCommand sqlCmd = new SqlCommand(sqlQuery, sqlConn); 58: sqlCmd.ExecuteNonQuery(); 59: sqlConn.Close(); 60: } 61: 62: } 63: private void LoadDataToDatabase(string tableName, string fileFullPath, string delimeter) 64: { 65: string sqlQuery = string.Empty; 66: StringBuilder sb = new StringBuilder(); 67: 68: sb.AppendFormat(string.Format("BULK INSERT {0} ", tableName)); 69: sb.AppendFormat(string.Format(" FROM '{0}'", fileFullPath)); 70: sb.AppendFormat(string.Format(" WITH ( FIELDTERMINATOR = '{0}' , ROWTERMINATOR = '\n' )", delimeter)); 71: 72: sqlQuery = sb.ToString(); 73: 74: using (SqlConnection sqlConn = new SqlConnection(GetConnectionString())) 75: { 76: sqlConn.Open(); 77: SqlCommand sqlCmd = new SqlCommand(sqlQuery, sqlConn); 78: sqlCmd.ExecuteNonQuery(); 79: sqlConn.Close(); 80: } 81: } 82: protected void Page_Load(object sender, EventArgs e) 83: { 84: 85: } 86: protected void BTNImport_Click(object sender, EventArgs e) 87: { 88: if (FileUpload1.HasFile) 89: { 90: FileInfo fileInfo = new FileInfo(FileUpload1.PostedFile.FileName); 91: if (fileInfo.Name.Contains(".csv")) 92: { 93: 94: string fileName = fileInfo.Name.Replace(".csv", "").ToString(); 95: string csvFilePath = Server.MapPath("UploadedCSVFiles") + "\\" + fileInfo.Name; 96: 97: //Save the CSV file in the Server inside 'MyCSVFolder' 98: FileUpload1.SaveAs(csvFilePath); 99: 100: //Fetch the location of CSV file 101: string filePath = Server.MapPath("UploadedCSVFiles") + "\\"; 102: string strSql = "SELECT * FROM [" + fileInfo.Name + "]"; 103: string strCSVConnString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + filePath + ";" + "Extended Properties='text;HDR=YES;'"; 104: 105: // load the data from CSV to DataTable 106: 107: OleDbDataAdapter adapter = new OleDbDataAdapter(strSql, strCSVConnString); 108: DataTable dtCSV = new DataTable(); 109: DataTable dtSchema = new DataTable(); 110: 111: adapter.FillSchema(dtCSV, SchemaType.Mapped); 112: adapter.Fill(dtCSV); 113: 114: if (dtCSV.Rows.Count > 0) 115: { 116: CreateDatabaseTable(dtCSV, fileName); 117: Label2.Text = string.Format("The table ({0}) has been successfully created to the database.", fileName); 118: 119: string fileFullPath = filePath + fileInfo.Name; 120: LoadDataToDatabase(fileName, fileFullPath, ","); 121: 122: Label1.Text = string.Format("({0}) records has been loaded to the table {1}.", dtCSV.Rows.Count, fileName); 123: } 124: else 125: { 126: LBLError.Text = "File is empty."; 127: } 128: } 129: else 130: { 131: LBLError.Text = "Unable to recognize file."; 132: } 133: 134: } 135: } 136: } 137: } The code above consists of three (3) private methods which are the GetConnectionString(), CreateDatabaseTable() and LoadDataToDatabase(). The GetConnectionString() is a method that returns a string. This method basically gets the connection string that is configured in the web.config file. The CreateDatabaseTable() is method that accepts two (2) parameters which are the DataTable and the filename. As the method name already suggested, this method automatically create a Table to the database based on the source DataTable and the filename of the CSV file. The LoadDataToDatabase() is a method that accepts three (3) parameters which are the tableName, fileFullPath and delimeter value. This method is where the actual saving or importing of data from CSV to SQL server happend. The codes at BTNImport_Click event handles the uploading of CSV file to the specified location and at the same time this is where the CreateDatabaseTable() and LoadDataToDatabase() are being called. If you notice I also added some basic trappings and validations within that event. Now to test the importing utility then let's create a simple data in a CSV format. Just for the simplicity of this demo let's create a CSV file and name it as "Employee" and add some data on it. Here's an example below: 1,VMS,Durano,[email protected] 2,Jennifer,Cortes,[email protected] 3,Xhaiden,Durano,[email protected] 4,Angel,Santos,[email protected] 5,Kier,Binks,[email protected] 6,Erika,Bird,[email protected] 7,Vianne,Durano,[email protected] 8,Lilibeth,Tree,[email protected] 9,Bon,Bolger,[email protected] 10,Brian,Jones,[email protected] Now save the newly created CSV file in some location in your hard drive. Okay let's run the application and browse the CSV file that we have just created. Take a look at the sample screen shots below: After browsing the CSV file. After clicking the Import Button Now if we look at the database that we have created earlier you'll notice that the Employee table is created with the imported data on it. See below screen shot. That's it! I hope someone find this post useful! Technorati Tags: ASP.NET,CSV,SQL,C#,ADO.NET

Read the article

Oracle @ AIIM Conference

- by [email protected]

Oracle will be at the AIIM Conference and Exposition next week in Philadelphia. On the opening morning, Robert Shimp, Group Vice President, Global Technology Business Unit, of Oracle Corporation, will moderate an executive keynote panel. Mr. Shimp will lead four Oracle customer executives through a lively discussion of how innovative organizations are driving the integration of content management with their core business processes on Tuesday April 20th at 8:45 AM. Our panelists are: CINDY BIXLER, CIO, Embry Riddle Aeronautical University TOM SHOWALTER, Managing Director, JP Morgan Chase IRFAN MOTIWALA, Vice President, Moody's Investors Service MIT MONICA CROCKER, CRM, PMP, Corporate Records Manager, Land O'Lakes For more information on our panelists, click here. Oracle will be in booth #2113 at the AIIM Expo. Come by and enter the daily raffle to win a Netbook! Oracle and Oracle partners will demonstrate solutions that increase productivity, reduce costs and ensure compliance for business processes such as accounts payable, human resource onboarding, marketing campaigns, sales management, large scale diagrams for facilities and manufacturing, case management, and others Oracle products including Oracle Universal Content Management, Oracle Imaging and Process Management, Oracle Universal Records Management, Oracle WebCenter, Oracle AutoVue, and Oracle Secure Enterprise Search will be demonstrated in the booth. Oracle will host a private event at The Field House Sports Bar - see your Oracle representative for more details Oracle customers can meet in private meeting rooms with their Oracle representatives Key Sessions Besides the opening morning keynote panel, Oracle will have a number of other sessions at the conference. Oracle Content Management will be featured in the session G08 - A Passage to Improving Healthcare: Enhancing EMR with Electronic Records Wednesday April 21st 2:25PM-3:10PM Kristina Parma of Oracle partner ImageSource will deliver this session, along with Pam Doyle of Fujitsu and Nancy Gladish of Swedish Medical Center. Kristina will also be in the Oracle booth to talk about this solution. On Tuesday April 20th at 4:05 PM Ajay Gandhi of Oracle will deliver a session entitled Harnessing SharePoint Content for Enterprise Processes in PeopleSoft, Siebel, E-Business Suite and JD Edwards Tuesday April 20th 1:15PM-1:45PM - Bringing Content Management to Your AP, HR, Sales and Marketing Processes - Application Showcase Theater (on the AIIM Expo Floor - Booth 1549 Wednesday April 21st 12:30PM-1:00PM - Embed and Edit Content Anywhere - Application Showcase Theater (on the AIIM Expo Floor - Booth 1549 For more information, see the AIIM Expo page on the Oracle website.

Read the article

Ground Control by David Baum

- by JuergenKress

As cloud computing moves out of the early-adopter phase, organizations are carefully evaluating how to get to the cloud. They are examining standard methods for developing, integrating, deploying, and scaling their cloud applications, and after weighing their choices, they are choosing to develop and deploy cloud applications based on Oracle Cloud Application Foundation, part of Oracle Fusion Middleware. Oracle WebLogic Server is the flagship software product of Oracle Cloud Application Foundation. Oracle WebLogic Server is optimized to run on Oracle Exalogic Elastic Cloud, the integrated hardware and software platform for the Oracle Cloud Application Foundation family. Many companies, including Reliance Commercial Finance, are adopting this middleware infrastructure to enable private cloud computing and its convenient, on-demand access to a shared pool of configurable computing resources. “Cloud computing has become an extremely critical design factor for us,” says Shashi Kumar Ravulapaty, senior vice president and chief technology officer at Reliance Commercial Finance. “It’s one of our main focus areas. Oracle Exalogic, especially in combination with Oracle WebLogic, is a perfect fit for rapidly provisioning capacity in a private cloud infrastructure.” Reliance Commercial Finance provides loans to tens of thousands of customers throughout India. With more than 1,500 employees accessing the company’s core business applications every day, the company was having trouble processing more than 6,000 daily transactions with its legacy infrastructure, especially at the end of each month when hundreds of concurrent users need to access the company’s loan processing and approval applications. Read the complete article here. WebLogic Partner Community For regular information become a member in the WebLogic Partner Community please visit: http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Wiki Technorati Tags: WebLogic,WebLogic Community,Oracle,OPN,Jürgen Kress

Search Results

Search found 15432 results on 618 pages for 'private inheritance'.

Page 183/618 | < Previous Page | 179 180 181 182 183 184 185 186 187 188 189 190 | Next Page >

- by rkb

- by BlueBeast

- by Alex

- by snipes83

- by James Michael Hare

- by Rhames

- by James Michael Hare

- by zowens

- by cibrax

- by Julian Assange

- by hyde

- by Mysticgeek

- by trond-arne.undheim

- by neil chen

- by Dixin

- by Rick Strahl

- by arungupta

- by arungupta

- by Edward Boyle

- by user22215

- by timramich

- by Edward Boyle

- by Vincent Maverick Durano

- by [email protected]

- by JuergenKress

< Previous Page | 179 180 181 182 183 184 185 186 187 188 189 190 | Next Page >