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  • Null reference but it's not?

    - by Clint Davis
    This is related to my previous question but it is a different problem. I have two classes: Server and Database. Public Class Server Private _name As String Public Property Name() As String Get Return _name End Get Set(ByVal value As String) _name = value End Set End Property Private _databases As List(Of Database) Public Property Databases() As List(Of Database) Get Return _databases End Get Set(ByVal value As List(Of Database)) _databases = value End Set End Property Public Sub LoadTables() Dim db As New Database(Me) db.Name = "test" Databases.Add(db) End Sub End Class Public Class Database Private _server As Server Private _name As String Public Property Name() As String Get Return _name End Get Set(ByVal value As String) _name = value End Set End Property Public Property Server() As Server Get Return _server End Get Set(ByVal value As Server) _server = value End Set End Property Public Sub New(ByVal ser As Server) Server = ser End Sub End Class Fairly simple. I use like this: Dim s As New Server s.Name = "Test" s.LoadTables() The problem is in the LoadTables in the Server class. When it hits Databases.Add(db) it gives me a NullReference error (Object reference not set). I don't understand how it is getting that, all the objects are set. Any ideas? Thanks.

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  • Global State and Singletons Dependency injection

    - by Manu
    this is a problem i face lot of times when i am designing a new app i'll use a sample problem to explain this think i am writing simple game.so i want to hold a list of players. i have few options.. 1.use a static field in some class private static ArrayList<Player> players = new ArrayList<Integer>(); public Player getPlayer(int i){ return players.get(i); } but this a global state 2.or i can use a singleton class PlayerList{ private PlayerList instance; private PlayerList(){...} public PlayerList getInstance() { if(instance==null){ ... } return instance; } } but this is bad because it's a singleton 3.Dependency injection class Game { private PlayerList playerList; public Game(PlayerList list) { this.list = list; } public PlayerList getPlayerList() { return playerList; } } this seems good but it's not, if any object outside Game need to look at PlayerList (which is the usual case) i have to use one of the above methods to make the Game class available globally. so I just add another layer to the problem. didn't actually solve anything. what is the optimum solution ? (currently i use Singleton approach)

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  • How to enforce DB field size limit to related Java String?

    - by Sri Sankaran
    What is the correct way to defend against trying to store more text than can be accommodated in a VARCHAR2 database field? Say the PARTNER_ROLE field of the REGISTRATIONS table is declared as VARCHAR2(80). This field is mapped in the Registration class in Java as public class Registration { @Column(name=”PARTNER_ROLE” length=”80”) private String partnerRole; } However, the setPartnerRole() method allows the user to stuff a string of any length. The problem is encountered only when one subsequently tries to insert or update the REGISTRATIONS record. Oracle complains. What is the correct way to handle this situation?

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  • NodeJS + Express: res.redirect('back'); with params

    - by Ilya Rusanen
    I have register form on every page of my website. During registration some error may occur. After cathing error, I have to return user to previous page, showing some error tips. The problem is I dont know from which page user performs registration. That's why I use res.redirect('back');. However, I cant just redirect user back, I have to show him whats wrong. Thats why I have to pass some parameter. But res.redirect('back', (reg_error:'username')}) can not be used directly 'cause res.redirect() doesn't support parameters. How can I render prevous page with some parameter? Thanks!

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  • How to make paging start from 1 instead of 0 in ASP.NET MVC

    - by ssx
    I used the paging example of the Nerddinner tutorial. But I also wanted to add page Numbers, somehting like that: <<< 1 2 3 4 5 6 The code below works if i start my paging from 0, but not from 1. How can I fix this ? Here is my code: PaginatedList.cs public class PaginatedList<T> : List<T> { public int PageIndex { get; private set; } public int PageSize { get; private set; } public int TotalCount { get; private set; } public int TotalPages { get; private set; } public PaginatedList(IQueryable<T> source, int pageIndex, int pageSize) { PageIndex = pageIndex; PageSize = pageSize; TotalCount = source.Count(); TotalPages = (int) Math.Ceiling(TotalCount / (double)PageSize); this.AddRange(source.Skip(PageIndex * PageSize).Take(PageSize)); } public bool HasPreviousPage { get { return (PageIndex > 0); } } public bool HasNextPage { get { return (PageIndex+1 < TotalPages); } } } UserController.cs public ActionResult List(int? page) { const int pageSize = 20; IUserRepository userRepository = new UserRepository(); IQueryable<User> listUsers = userRepository.GetAll(); PaginatedList<User> paginatedUsers = new PaginatedList<User>(listUsers, page ?? 0, pageSize); return View(paginatedUsers); } List.cshtml @if (Model.HasPreviousPage) { @Html.RouteLink(" Previous ", "PaginatedUsers", new { page = (Model.PageIndex - 1) }) } @for (int i = 1; i <= Model.TotalPages; i++) { @Html.RouteLink(@i.ToString(), "PaginatedUsers", new { page = (@i ) }) } @if (Model.HasNextPage) { @Html.RouteLink(" Next ", "PaginatedUsers", new { page = (Model.PageIndex + 1) }) }

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  • Google Cloud Messaging

    - by atar
    I downloaded the GCM project from git and i was able to start the server (app engine for java) and also compile the client apk on the device. On startup the device successfully registers with the server and I can see the registration id when i go to http://myserverip:8080/_ah/admin/. The problem is when i hit the 'Send Message' button there is a message 'Single message queued for registration id ' and it doesn't do anything. Below is a screenshot of the error i noticed on the terminal. Am i missing something. Any help is appreciated. Thanks. .

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  • Something wrong on my very first LINQ to SQL c # code

    - by user334813
    using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; namespace Advanced_LinQ_Query { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private DataClasses1DataContext database = new DataClasses1DataContext(); private void Form1_Load(object sender, EventArgs e) { database.Log= Console.Out; comboBox.SelectedIndex=0; } private void titleBindingNavigatorSaveItem_Click(object sender, EventArgs e) { Validate(); titleBindingSource.EndEdit(); database.SubmitChanges(); comboBox.SelectedIndex=0; } private void comboBox_SelectedIndexChanged(object sender, EventArgs e) { switch (comboBox.SelectedIndex) { case 0: titleBindingSource.DataSource = from Title in database.Titles orderby Title.BookTitle select Title; break; case 1: titleBindingSource.DataSource = from Title in database.Titles where Title.Copyright == "2008" orderby Title.BookTitle select Title; break; case 2: titleBindingSource.DataSource = from Title in database.Titles where Title.BookTitle.EndsWith("How to Program") orderby Title.BookTitle select Title; break; } titleBindingSource.MoveFirst(); } } } no connection seems to built after debugging between Title table in my database (book.mdf) and titleBindingSource! Where is the problem?

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  • pass variable by reference within class? in php

    - by user151841
    I'm working on a hex color class where you can change the color values of any hex code color. In my example, I haven't finished the hex math, but it's not completely relevant to what I'm explaining here. Naively, I wanted to start to do something that I don't think can be done. I wanted to pass object properties in a method call. Is this possible? class rgb { private $r; private $b; private $g; public function __construct( $hexRgb ) { $this->r = substr($hexRgb, 0, 2 ); $this->g = substr($hexRgb, 2, 2 ); $this->b = substr($hexRgb, 4, 2 ); } private function add( & $color, $amount ) { $color += amount; // $color should be a class property, $this->r, etc. } public function addRed( $amount ) { self::add( $this->r, $amount ); } public function addGreen( $amount ) { self::add( $this->g, $amount ); } public function addBlue( $amount ) { self::add( $this->b, $amount ); } } If this is not possible in PHP, what is this called and in what languages is it possible? I know I could do something like public function add( $var, $amount ) { if ( $var == "r" ) { $this->r += $amount } else if ( $var == "g" ) { $this->g += $amount } ... } But I want to do it this cool way.

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  • Javascript object properties access functions in parent constructor?

    - by Bob Spryn
    So I'm using this pretty standard jquery plugin pattern whereby you can grab an api after applying the jquery function to a specific instance. This API is essentially a javascript object with a bunch of methods and data. So I wanted to essentially create some private internal methods for the object only to manipulate data etc, which just doesn't need to be available as part of the API. So I tried this: // API returned with new $.TranslationUI(options, container) $.TranslationUI = function (options, container) { // private function? function monkey(){ console.log("blah blah blah"); } // extend the default settings with the options object passed this.settings = $.extend({},$.TranslationUI.defaultSettings,options); // set a reference for the container dom element this.container = container; // call the init function this.init(); }; The problem I'm running into is that init can't call that function "monkey". I'm not understanding the explanation behind why it can't. Is it because init is a prototype method?($.TranslationUI's prototype is extended with a bunch of methods including init elsewhere in the code) $.extend($.TranslationUI, { prototype: { init : function(){ // doesn't work monkey(); // editing flag this.editing = false; // init event delegates here for // languagepicker $(this.settings.languageSelector, this.container).bind("click", {self: this}, this.selectLanguage); } } }); Any explanations would be helpful. Would love other thoughts on creating private methods with this model too. These particular functions don't HAVE to be in prototype, and I don't NEED private methods protected from being used externally, but I want to know how should I have that requirement in the future.

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  • Preserving the order of annotations

    - by Ragunath Jawahar
    When obtaining the list of fields using getFields() and getDeclaredFields(), the order of the fields in a Java class is undefined. I need this order in my validation library. Since the order is not preserved (though some claim that the order is preserved in JDK 6 and above but is not guaranteed across VMs). I cannot speculate on this because the order of annotations across fields is absolutely essential for the library. One way to get around this is to have an order or an index attribute in my Annotation. What worries me is that the code could become a bit cumbersome for maintaining in the following case. If the use wants to insert a new annotated field then, he might have to renumber all the other annotations in the class. I could have the order or index as a floating point number - float or double but , it wouldn't look good to have order such as 1, 1.5, 2, etc., What would be an elegant solution for this problem? Here is a example code so that you can get an idea about the problem: @Required @TextRule (minLength = 6, message = "You need at least 6 characters.") private EditText usernameEditText; @Password private EditText passwordEditText; @ConfirmPassword private EditText confirmPasswordEditText; @Email private EditText emailEditText;

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  • Is fetching data from database a get-method thing?

    - by theva
    I have a small class that I call Viewer. This class is supposed to view the proper layout of each page or something like that... I have a method called getFirstPage, when called the user of this method will get a setting value for which page is currently set as the first page. I have some code here, I think it works but I am not really shure that I have done it the right way: class Viewer { private $db; private $user; private $firstPage; function __construct($db, $user) { $this->db = $db; if(isset($user)) { $this->user = $user; } else { $this->user = 'default'; } } function getFistPage() { $std = $db->prepare("SELECT firstPage FROM settings WHERE user = ':user'"); $std->execute(array(':user' => $user)); $result = $std->fetch(); $this->firstPage = $result['firstPage']; return $this->firstPage; } } My get method is fetching the setting from databse (so far so good?). The problem is that then I have to use this get method to set the private variable firstPage. It seems like I should have a set method to do this, but I cannot really have a set method that just fetch some setting from database, right? Because the user of this object should be able to assume that there already is a setting defined in the object... How should I do that?

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  • Accessing Application Scoped Bean Causes NullPointerException

    - by user2946861
    What is an Application Scoped Bean? I understand it to be a bean which will exist for the life of the application, but that doesn't appear to be the correct interpretation. I have an application which creates an application scoped bean on startup (eager=true) and then a session bean that tries to access the application scoped bean's objects (which are also application scoped). But when I try to access the application scoped bean from the session scoped bean, I get a null pointer exception. Here's excerpts from my code: Application Scoped Bean: @ManagedBean(eager=true) @ApplicationScoped public class Bean1 implements Serializable{ private static final long serialVersionUID = 12345L; protected ArrayList<App> apps; // construct apps so they are available for the session scoped bean // do time consuming stuff... // getters + setters Session Scoped Bean: @ManagedBean @SessionScoped public class Bean2 implements Serializable{ private static final long serialVersionUID = 123L; @Inject private Bean1 bean1; private ArrayList<App> apps = bean1.getApps(); // null pointer exception What appears to be happening is, Bean1 is created, does it's stuff, then is destroyed before Bean2 can access it. I was hoping using application scoped would keep Bean1 around until the container was shutdown, or the application was killed, but this doesn't appear to be the case.

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  • How to send Message to all registered users with android gcm?

    - by FlyBy
    I am using android gcm to make push notifications for my users. Everything is working so fine. To send a notification I need the users registration id to identify him. It works. Now my problem is that I have some hundreds of users and I would like to inform them ALL about certain updates. Is there a way to send a notification to all users? Do I really have to push them all by their registration ids? On the server side I am using PHP and CURL as it is shown in many examples around here...

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  • Is the below thread pool implementation correct(C#3.0)

    - by Newbie
    Hi Experts, For the first time ever I have implemented thread pooling and I found it to be working. But I am not very sure about the way I have done is the appropriate way it is supposed to be. Would you people mind in spending some valuable time to check and let me know if my approach is correct or not? If you people find that the approach is incorrect , could you please help me out in writing the correct version. I have basicaly read How to use thread pool and based on what ever I have understood I have developed the below program as per my need public class Calculation { #region Private variable declaration ManualResetEvent[] factorManualResetEvent = null; #endregion public void Compute() { factorManualResetEvent = new ManualResetEvent[2]; for (int i = 0; i < 2; i++){ factorManualResetEvent[i] = new ManualResetEvent(false); ThreadPool.QueueUserWorkItem(ThreadPoolCallback, i);} //Wait for all the threads to complete WaitHandle.WaitAll(factorManualResetEvent); //Proceed with the next task(s) NEXT_TASK_TO_BE_EXECUTED(); } #region Private Methods // Wrapper method for use with thread pool. public void ThreadPoolCallback(Object threadContext) { int threadIndex = (int)threadContext; Method1(); Method2(); factorManualResetEvent[threadIndex].Set(); } private void Method1 () { //Code of method 1} private void Method2 () { //Code of method 2 } #endregion }

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  • Java PropertyChangeListener

    - by Laphroaig
    Hi, i'm trying to figure out how to listen a property change on another class. this is my code: class with the property to listen: public class ClassWithProperty { private PropertyChangeSupport changes = new PropertyChangeSupport(this); private int usersOnline; public int getUsersOnline() { return usersOnline; } public ClassWithProperty() { usersOnline = 0; while (usersOnline<10) { changes.firePropertyChange("usersOnline", usersOnline, usersOnline++); } } public void addPropertyChangeListener( PropertyChangeListener l) { changes.addPropertyChangeListener(l); } public void removePropertyChangeListener( PropertyChangeListener l) { changes.removePropertyChangeListener(l); } } class where i need to know when the property change: public class Main { private static ClassWithProperty test; public static void main(String[] args) { test = new ClassWithProperty(); test.addPropertyChangeListener(listen()); } private static PropertyChangeListener listen() { System.out.println(test.getUsersOnline()); return null; } } I have the event fired only the last time (usersOnline=10). Sorry if it can be a stupid question, i'm learning now java and can't find a solution.

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  • How can I bind the same dependency to many dependents in Ninject?

    - by Mike Bantegui
    Let's I have three interfaces: IFoo, IBar, IBaz. I also have the classes Foo, Bar, and Baz that are the respective implementations. In the implementations, each depends on the interface IContainer. So for the Foo (and similarly for Bar and Baz) the implementation might read: class Foo : IFoo { private readonly IDependency Dependency; public Foo(IDependency dependency) { Dependency = dependency; } public void Execute() { Console.WriteLine("I'm using {0}", Dependency.Name); } } Let's furthermore say I have a class Container which happens to contain instances of the IFoo, IBar and IBaz: class Container : IContainer { private readonly IFoo _Foo; private readonly IBar _Bar; private readonly IBaz _Baz; public Container(IFoo foo, IBar bar, IBaz baz) { _Foo = foo; _Bar = bar; _Baz = baz; } } In this scenario, I would like the implementation class Container to bind against IContainer with the constraint that the IDependency that gets injected into IFoo, IBar, and IBaz be the same for all three. In the manual way, I might implement it as: IDependency dependency = new Dependency(); IFoo foo = new Foo(dependency); IBar bar = new Bar(dependency); IBaz baz = new Baz(dependency); IContainer container = new Container(foo, bar, baz); How can I achieve this within Ninject? Note: I am not asking how to do nested dependencies. My question is how I can guarantee that a given dependency is the same among a collection of objects within a materialized service. To be extremely explicit, I understand that Ninject in it's standard form will generate code that is equivalent to the following: IContainer container = new Container(new Foo(new Dependency()), new Bar(new Dependency()), new Baz(new Dependency())); I would not like that behavior.

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  • Problem in thread pool implementation(C#3.0)

    - by Newbie
    Hi Experts, I have done the below thread pool program but the problem is that the WaitCallBackMethod(here ThreadPoolCallback) is getting called 2 times(which ideally should be called 1ce). what is the misktake I am making? public class Calculation { #region Private variable declaration ManualResetEvent[] factorManualResetEvent = null; #endregion public void Compute() { factorManualResetEvent = new ManualResetEvent[2]; for (int i = 0; i < 2; i++){ factorManualResetEvent[i] = new ManualResetEvent(false); ThreadPool.QueueUserWorkItem(ThreadPoolCallback, i);} //Wait for all the threads to complete WaitHandle.WaitAll(factorManualResetEvent); //Proceed with the next task(s) NEXT_TASK_TO_BE_EXECUTED(); } #region Private Methods // Wrapper method for use with thread pool. public void ThreadPoolCallback(Object threadContext) { int threadIndex = (int)threadContext; Method1(); Method2(); factorManualResetEvent[threadIndex].Set(); } private void Method1 () { //Code of method 1} private void Method2 () { //Code of method 2 } #endregion } I am using C#3.0 Thanks

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  • From Binary to Data Structures

    - by Cédric Menzi
    Table of Contents Introduction PE file format and COFF header COFF file header BaseCoffReader Byte4ByteCoffReader UnsafeCoffReader ManagedCoffReader Conclusion History This article is also available on CodeProject Introduction Sometimes, you want to parse well-formed binary data and bring it into your objects to do some dirty stuff with it. In the Windows world most data structures are stored in special binary format. Either we call a WinApi function or we want to read from special files like images, spool files, executables or may be the previously announced Outlook Personal Folders File. Most specifications for these files can be found on the MSDN Libarary: Open Specification In my example, we are going to get the COFF (Common Object File Format) file header from a PE (Portable Executable). The exact specification can be found here: PECOFF PE file format and COFF header Before we start we need to know how this file is formatted. The following figure shows an overview of the Microsoft PE executable format. Source: Microsoft Our goal is to get the PE header. As we can see, the image starts with a MS-DOS 2.0 header with is not important for us. From the documentation we can read "...After the MS DOS stub, at the file offset specified at offset 0x3c, is a 4-byte...". With this information we know our reader has to jump to location 0x3c and read the offset to the signature. The signature is always 4 bytes that ensures that the image is a PE file. The signature is: PE\0\0. To prove this we first seek to the offset 0x3c, read if the file consist the signature. So we need to declare some constants, because we do not want magic numbers.   private const int PeSignatureOffsetLocation = 0x3c; private const int PeSignatureSize = 4; private const string PeSignatureContent = "PE";   Then a method for moving the reader to the correct location to read the offset of signature. With this method we always move the underlining Stream of the BinaryReader to the start location of the PE signature.   private void SeekToPeSignature(BinaryReader br) { // seek to the offset for the PE signagure br.BaseStream.Seek(PeSignatureOffsetLocation, SeekOrigin.Begin); // read the offset int offsetToPeSig = br.ReadInt32(); // seek to the start of the PE signature br.BaseStream.Seek(offsetToPeSig, SeekOrigin.Begin); }   Now, we can check if it is a valid PE image by reading of the next 4 byte contains the content PE.   private bool IsValidPeSignature(BinaryReader br) { // read 4 bytes to get the PE signature byte[] peSigBytes = br.ReadBytes(PeSignatureSize); // convert it to a string and trim \0 at the end of the content string peContent = Encoding.Default.GetString(peSigBytes).TrimEnd('\0'); // check if PE is in the content return peContent.Equals(PeSignatureContent); }   With this basic functionality we have a good base reader class to try the different methods of parsing the COFF file header. COFF file header The COFF header has the following structure: Offset Size Field 0 2 Machine 2 2 NumberOfSections 4 4 TimeDateStamp 8 4 PointerToSymbolTable 12 4 NumberOfSymbols 16 2 SizeOfOptionalHeader 18 2 Characteristics If we translate this table to code, we get something like this:   [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)] public struct CoffHeader { public MachineType Machine; public ushort NumberOfSections; public uint TimeDateStamp; public uint PointerToSymbolTable; public uint NumberOfSymbols; public ushort SizeOfOptionalHeader; public Characteristic Characteristics; } BaseCoffReader All readers do the same thing, so we go to the patterns library in our head and see that Strategy pattern or Template method pattern is sticked out in the bookshelf. I have decided to take the template method pattern in this case, because the Parse() should handle the IO for all implementations and the concrete parsing should done in its derived classes.   public CoffHeader Parse() { using (var br = new BinaryReader(File.Open(_fileName, FileMode.Open, FileAccess.Read, FileShare.Read))) { SeekToPeSignature(br); if (!IsValidPeSignature(br)) { throw new BadImageFormatException(); } return ParseInternal(br); } } protected abstract CoffHeader ParseInternal(BinaryReader br);   First we open the BinaryReader, seek to the PE signature then we check if it contains a valid PE signature and rest is done by the derived implementations. Byte4ByteCoffReader The first solution is using the BinaryReader. It is the general way to get the data. We only need to know which order, which data-type and its size. If we read byte for byte we could comment out the first line in the CoffHeader structure, because we have control about the order of the member assignment.   protected override CoffHeader ParseInternal(BinaryReader br) { CoffHeader coff = new CoffHeader(); coff.Machine = (MachineType)br.ReadInt16(); coff.NumberOfSections = (ushort)br.ReadInt16(); coff.TimeDateStamp = br.ReadUInt32(); coff.PointerToSymbolTable = br.ReadUInt32(); coff.NumberOfSymbols = br.ReadUInt32(); coff.SizeOfOptionalHeader = (ushort)br.ReadInt16(); coff.Characteristics = (Characteristic)br.ReadInt16(); return coff; }   If the structure is as short as the COFF header here and the specification will never changed, there is probably no reason to change the strategy. But if a data-type will be changed, a new member will be added or ordering of member will be changed the maintenance costs of this method are very high. UnsafeCoffReader Another way to bring the data into this structure is using a "magically" unsafe trick. As above, we know the layout and order of the data structure. Now, we need the StructLayout attribute, because we have to ensure that the .NET Runtime allocates the structure in the same order as it is specified in the source code. We also need to enable "Allow unsafe code (/unsafe)" in the project's build properties. Then we need to add the following constructor to the CoffHeader structure.   [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)] public struct CoffHeader { public CoffHeader(byte[] data) { unsafe { fixed (byte* packet = &data[0]) { this = *(CoffHeader*)packet; } } } }   The "magic" trick is in the statement: this = *(CoffHeader*)packet;. What happens here? We have a fixed size of data somewhere in the memory and because a struct in C# is a value-type, the assignment operator = copies the whole data of the structure and not only the reference. To fill the structure with data, we need to pass the data as bytes into the CoffHeader structure. This can be achieved by reading the exact size of the structure from the PE file.   protected override CoffHeader ParseInternal(BinaryReader br) { return new CoffHeader(br.ReadBytes(Marshal.SizeOf(typeof(CoffHeader)))); }   This solution is the fastest way to parse the data and bring it into the structure, but it is unsafe and it could introduce some security and stability risks. ManagedCoffReader In this solution we are using the same approach of the structure assignment as above. But we need to replace the unsafe part in the constructor with the following managed part:   [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)] public struct CoffHeader { public CoffHeader(byte[] data) { IntPtr coffPtr = IntPtr.Zero; try { int size = Marshal.SizeOf(typeof(CoffHeader)); coffPtr = Marshal.AllocHGlobal(size); Marshal.Copy(data, 0, coffPtr, size); this = (CoffHeader)Marshal.PtrToStructure(coffPtr, typeof(CoffHeader)); } finally { Marshal.FreeHGlobal(coffPtr); } } }     Conclusion We saw that we can parse well-formed binary data to our data structures using different approaches. The first is probably the clearest way, because we know each member and its size and ordering and we have control about the reading the data for each member. But if add member or the structure is going change by some reason, we need to change the reader. The two other solutions use the approach of the structure assignment. In the unsafe implementation we need to compile the project with the /unsafe option. We increase the performance, but we get some security risks.

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  • Creating a dynamic proxy generator with c# – Part 2 – Interceptor Design

    - by SeanMcAlinden
    Creating a dynamic proxy generator – Part 1 – Creating the Assembly builder, Module builder and caching mechanism For the latest code go to http://rapidioc.codeplex.com/ Before getting too involved in generating the proxy, I thought it would be worth while going through the intended design, this is important as the next step is to start creating the constructors for the proxy. Each proxy derives from a specified type The proxy has a corresponding constructor for each of the base type constructors The proxy has overrides for all methods and properties marked as Virtual on the base type For each overridden method, there is also a private method whose sole job is to call the base method. For each overridden method, a delegate is created whose sole job is to call the private method that calls the base method. The following class diagram shows the main classes and interfaces involved in the interception process. I’ll go through each of them to explain their place in the overall proxy.   IProxy Interface The proxy implements the IProxy interface for the sole purpose of adding custom interceptors. This allows the created proxy interface to be cast as an IProxy and then simply add Interceptors by calling it’s AddInterceptor method. This is done internally within the proxy building process so the consumer of the API doesn’t need knowledge of this. IInterceptor Interface The IInterceptor interface has one method: Handle. The handle method accepts a IMethodInvocation parameter which contains methods and data for handling method interception. Multiple classes that implement this interface can be added to the proxy. Each method override in the proxy calls the handle method rather than simply calling the base method. How the proxy fully works will be explained in the next section MethodInvocation. IMethodInvocation Interface & MethodInvocation class The MethodInvocation will contain one main method and multiple helper properties. Continue Method The method Continue() has two functions hidden away from the consumer. When Continue is called, if there are multiple Interceptors, the next Interceptors Handle method is called. If all Interceptors Handle methods have been called, the Continue method then calls the base class method. Properties The MethodInvocation will contain multiple helper properties including at least the following: Method Name (Read Only) Method Arguments (Read and Write) Method Argument Types (Read Only) Method Result (Read and Write) – this property remains null if the method return type is void Target Object (Read Only) Return Type (Read Only) DefaultInterceptor class The DefaultInterceptor class is a simple class that implements the IInterceptor interface. Here is the code: DefaultInterceptor namespace Rapid.DynamicProxy.Interception {     /// <summary>     /// Default interceptor for the proxy.     /// </summary>     /// <typeparam name="TBase">The base type.</typeparam>     public class DefaultInterceptor<TBase> : IInterceptor<TBase> where TBase : class     {         /// <summary>         /// Handles the specified method invocation.         /// </summary>         /// <param name="methodInvocation">The method invocation.</param>         public void Handle(IMethodInvocation<TBase> methodInvocation)         {             methodInvocation.Continue();         }     } } This is automatically created in the proxy and is the first interceptor that each method override calls. It’s sole function is to ensure that if no interceptors have been added, the base method is still called. Custom Interceptor Example A consumer of the Rapid.DynamicProxy API could create an interceptor for logging when the FirstName property of the User class is set. Just for illustration, I have also wrapped a transaction around the methodInvocation.Coninue() method. This means that any overriden methods within the user class will run within a transaction scope. MyInterceptor public class MyInterceptor : IInterceptor<User<int, IRepository>> {     public void Handle(IMethodInvocation<User<int, IRepository>> methodInvocation)     {         if (methodInvocation.Name == "set_FirstName")         {             Logger.Log("First name seting to: " + methodInvocation.Arguments[0]);         }         using (TransactionScope scope = new TransactionScope())         {             methodInvocation.Continue();         }         if (methodInvocation.Name == "set_FirstName")         {             Logger.Log("First name has been set to: " + methodInvocation.Arguments[0]);         }     } } Overridden Method Example To show a taster of what the overridden methods on the proxy would look like, the setter method for the property FirstName used in the above example would look something similar to the following (this is not real code but will look similar): set_FirstName public override void set_FirstName(string value) {     set_FirstNameBaseMethodDelegate callBase =         new set_FirstNameBaseMethodDelegate(this.set_FirstNameProxyGetBaseMethod);     object[] arguments = new object[] { value };     IMethodInvocation<User<IRepository>> methodInvocation =         new MethodInvocation<User<IRepository>>(this, callBase, "set_FirstName", arguments, interceptors);          this.Interceptors[0].Handle(methodInvocation); } As you can see, a delegate instance is created which calls to a private method on the class, the private method calls the base method and would look like the following: calls base setter private void set_FirstNameProxyGetBaseMethod(string value) {     base.set_FirstName(value); } The delegate is invoked when methodInvocation.Continue() is called within an interceptor. The set_FirstName parameters are loaded into an object array. The current instance, delegate, method name and method arguments are passed into the methodInvocation constructor (there will be more data not illustrated here passed in when created including method info, return types, argument types etc.) The DefaultInterceptor’s Handle method is called with the methodInvocation instance as it’s parameter. Obviously methods can have return values, ref and out parameters etc. in these cases the generated method override body will be slightly different from above. I’ll go into more detail on these aspects as we build them. Conclusion I hope this has been useful, I can’t guarantee that the proxy will look exactly like the above, but at the moment, this is pretty much what I intend to do. Always worth downloading the code at http://rapidioc.codeplex.com/ to see the latest. There will also be some tests that you can debug through to help see what’s going on. Cheers, Sean.

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  • Custom Lookup Provider For NetBeans Platform CRUD Tutorial

    - by Geertjan
    For a long time I've been planning to rewrite the second part of the NetBeans Platform CRUD Application Tutorial to integrate the loosely coupled capabilities introduced in a seperate series of articles based on articles by Antonio Vieiro (a great series, by the way). Nothing like getting into the Lookup stuff right from the get go (rather than as an afterthought)! The question, of course, is how to integrate the loosely coupled capabilities in a logical way within that tutorial. Today I worked through the tutorial from scratch, up until the point where the prototype is completed, i.e., there's a JTextArea displaying data pulled from a database. That brought me to the place where I needed to be. In fact, as soon as the prototype is completed, i.e., the database connection has been shown to work, the whole story about Lookup.Provider and InstanceContent should be introduced, so that all the subsequent sections, i.e., everything within "Integrating CRUD Functionality" will be done by adding new capabilities to the Lookup.Provider. However, before I perform open heart surgery on that tutorial, I'd like to run the scenario by all those reading this blog who understand what I'm trying to do! (I.e., probably anyone who has read this far into this blog entry.) So, this is what I propose should happen and in this order: Point out the fact that right now the database access code is found directly within our TopComponent. Not good. Because you're mixing view code with data code and, ideally, the developers creating the user interface wouldn't need to know anything about the data access layer. Better to separate out the data access code into a separate class, within the CustomerLibrary module, i.e., far away from the module providing the user interface, with this content: public class CustomerDataAccess { public List<Customer> getAllCustomers() { return Persistence.createEntityManagerFactory("CustomerLibraryPU"). createEntityManager().createNamedQuery("Customer.findAll").getResultList(); } } Point out the fact that there is a concept of "Lookup" (which readers of the tutorial should know about since they should have followed the NetBeans Platform Quick Start), which is a registry into which objects can be published and to which other objects can be listening. In the same way as a TopComponent provides a Lookup, as demonstrated in the NetBeans Platform Quick Start, your own object can also provide a Lookup. So, therefore, let's provide a Lookup for Customer objects.  import org.openide.util.Lookup; import org.openide.util.lookup.AbstractLookup; import org.openide.util.lookup.InstanceContent; public class CustomerLookupProvider implements Lookup.Provider { private Lookup lookup; private InstanceContent instanceContent; public CustomerLookupProvider() { // Create an InstanceContent to hold capabilities... instanceContent = new InstanceContent(); // Create an AbstractLookup to expose the InstanceContent... lookup = new AbstractLookup(instanceContent); // Add a "Read" capability to the Lookup of the provider: //...to come... // Add a "Update" capability to the Lookup of the provider: //...to come... // Add a "Create" capability to the Lookup of the provider: //...to come... // Add a "Delete" capability to the Lookup of the provider: //...to come... } @Override public Lookup getLookup() { return lookup; } } Point out the fact that, in the same way as we can publish an object into the Lookup of a TopComponent, we can now also publish an object into the Lookup of our CustomerLookupProvider. Instead of publishing a String, as in the NetBeans Platform Quick Start, we'll publish an instance of our own type. And here is the type: public interface ReadCapability { public void read() throws Exception; } And here is an implementation of our type added to our Lookup: public class CustomerLookupProvider implements Lookup.Provider { private Set<Customer> customerSet; private Lookup lookup; private InstanceContent instanceContent; public CustomerLookupProvider() { customerSet = new HashSet<Customer>(); // Create an InstanceContent to hold capabilities... instanceContent = new InstanceContent(); // Create an AbstractLookup to expose the InstanceContent... lookup = new AbstractLookup(instanceContent); // Add a "Read" capability to the Lookup of the provider: instanceContent.add(new ReadCapability() { @Override public void read() throws Exception { ProgressHandle handle = ProgressHandleFactory.createHandle("Loading..."); handle.start(); customerSet.addAll(new CustomerDataAccess().getAllCustomers()); handle.finish(); } }); // Add a "Update" capability to the Lookup of the provider: //...to come... // Add a "Create" capability to the Lookup of the provider: //...to come... // Add a "Delete" capability to the Lookup of the provider: //...to come... } @Override public Lookup getLookup() { return lookup; } public Set<Customer> getCustomers() { return customerSet; } } Point out that we can now create a new instance of our Lookup (in some other module, so long as it has a dependency on the module providing the CustomerLookupProvider and the ReadCapability), retrieve the ReadCapability, and then do something with the customers that are returned, here in the rewritten constructor of the TopComponent, without needing to know anything about how the database access is actually achieved since that is hidden in the implementation of our type, above: public CustomerViewerTopComponent() { initComponents(); setName(Bundle.CTL_CustomerViewerTopComponent()); setToolTipText(Bundle.HINT_CustomerViewerTopComponent()); // EntityManager entityManager = Persistence.createEntityManagerFactory("CustomerLibraryPU").createEntityManager(); // Query query = entityManager.createNamedQuery("Customer.findAll"); // List<Customer> resultList = query.getResultList(); // for (Customer c : resultList) { // jTextArea1.append(c.getName() + " (" + c.getCity() + ")" + "\n"); // } CustomerLookupProvider lookup = new CustomerLookupProvider(); ReadCapability rc = lookup.getLookup().lookup(ReadCapability.class); try { rc.read(); for (Customer c : lookup.getCustomers()) { jTextArea1.append(c.getName() + " (" + c.getCity() + ")" + "\n"); } } catch (Exception ex) { Exceptions.printStackTrace(ex); } } Does the above make as much sense to others as it does to me, including the naming of the classes? Feedback would be appreciated! Then I'll integrate into the tutorial and do the same for the other sections, i.e., "Create", "Update", and "Delete". (By the way, of course, the tutorial ends up showing that, rather than using a JTextArea to display data, you can use Nodes and explorer views to do so.)

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  • Pluggable Rules for Entity Framework Code First

    - by Ricardo Peres
    Suppose you want a system that lets you plug custom validation rules on your Entity Framework context. The rules would control whether an entity can be saved, updated or deleted, and would be implemented in plain .NET. Yes, I know I already talked about plugable validation in Entity Framework Code First, but this is a different approach. An example API is in order, first, a ruleset, which will hold the collection of rules: 1: public interface IRuleset : IDisposable 2: { 3: void AddRule<T>(IRule<T> rule); 4: IEnumerable<IRule<T>> GetRules<T>(); 5: } Next, a rule: 1: public interface IRule<T> 2: { 3: Boolean CanSave(T entity, DbContext ctx); 4: Boolean CanUpdate(T entity, DbContext ctx); 5: Boolean CanDelete(T entity, DbContext ctx); 6: String Name 7: { 8: get; 9: } 10: } Let’s analyze what we have, starting with the ruleset: Only has methods for adding a rule, specific to an entity type, and to list all rules of this entity type; By implementing IDisposable, we allow it to be cancelled, by disposing of it when we no longer want its rules to be applied. A rule, on the other hand: Has discrete methods for checking if a given entity can be saved, updated or deleted, which receive as parameters the entity itself and a pointer to the DbContext to which the ruleset was applied; Has a name property for helping us identifying what failed. A ruleset really doesn’t need a public implementation, all we need is its interface. The private (internal) implementation might look like this: 1: sealed class Ruleset : IRuleset 2: { 3: private readonly IDictionary<Type, HashSet<Object>> rules = new Dictionary<Type, HashSet<Object>>(); 4: private ObjectContext octx = null; 5:  6: internal Ruleset(ObjectContext octx) 7: { 8: this.octx = octx; 9: } 10:  11: public void AddRule<T>(IRule<T> rule) 12: { 13: if (this.rules.ContainsKey(typeof(T)) == false) 14: { 15: this.rules[typeof(T)] = new HashSet<Object>(); 16: } 17:  18: this.rules[typeof(T)].Add(rule); 19: } 20:  21: public IEnumerable<IRule<T>> GetRules<T>() 22: { 23: if (this.rules.ContainsKey(typeof(T)) == true) 24: { 25: foreach (IRule<T> rule in this.rules[typeof(T)]) 26: { 27: yield return (rule); 28: } 29: } 30: } 31:  32: public void Dispose() 33: { 34: this.octx.SavingChanges -= RulesExtensions.OnSaving; 35: RulesExtensions.rulesets.Remove(this.octx); 36: this.octx = null; 37:  38: this.rules.Clear(); 39: } 40: } Basically, this implementation: Stores the ObjectContext of the DbContext to which it was created for, this is so that later we can remove the association; Has a collection - a set, actually, which does not allow duplication - of rules indexed by the real Type of an entity (because of proxying, an entity may be of a type that inherits from the class that we declared); Has generic methods for adding and enumerating rules of a given type; Has a Dispose method for cancelling the enforcement of the rules. A (really dumb) rule applied to Product might look like this: 1: class ProductRule : IRule<Product> 2: { 3: #region IRule<Product> Members 4:  5: public String Name 6: { 7: get 8: { 9: return ("Rule 1"); 10: } 11: } 12:  13: public Boolean CanSave(Product entity, DbContext ctx) 14: { 15: return (entity.Price > 10000); 16: } 17:  18: public Boolean CanUpdate(Product entity, DbContext ctx) 19: { 20: return (true); 21: } 22:  23: public Boolean CanDelete(Product entity, DbContext ctx) 24: { 25: return (true); 26: } 27:  28: #endregion 29: } The DbContext is there because we may need to check something else in the database before deciding whether to allow an operation or not. And here’s how to apply this mechanism to any DbContext, without requiring the usage of a subclass, by means of an extension method: 1: public static class RulesExtensions 2: { 3: private static readonly MethodInfo getRulesMethod = typeof(IRuleset).GetMethod("GetRules"); 4: internal static readonly IDictionary<ObjectContext, Tuple<IRuleset, DbContext>> rulesets = new Dictionary<ObjectContext, Tuple<IRuleset, DbContext>>(); 5:  6: private static Type GetRealType(Object entity) 7: { 8: return (entity.GetType().Assembly.IsDynamic == true ? entity.GetType().BaseType : entity.GetType()); 9: } 10:  11: internal static void OnSaving(Object sender, EventArgs e) 12: { 13: ObjectContext octx = sender as ObjectContext; 14: IRuleset ruleset = rulesets[octx].Item1; 15: DbContext ctx = rulesets[octx].Item2; 16:  17: foreach (ObjectStateEntry entry in octx.ObjectStateManager.GetObjectStateEntries(EntityState.Added)) 18: { 19: Object entity = entry.Entity; 20: Type realType = GetRealType(entity); 21:  22: foreach (dynamic rule in (getRulesMethod.MakeGenericMethod(realType).Invoke(ruleset, null) as IEnumerable)) 23: { 24: if (rule.CanSave(entity, ctx) == false) 25: { 26: throw (new Exception(String.Format("Cannot save entity {0} due to rule {1}", entity, rule.Name))); 27: } 28: } 29: } 30:  31: foreach (ObjectStateEntry entry in octx.ObjectStateManager.GetObjectStateEntries(EntityState.Deleted)) 32: { 33: Object entity = entry.Entity; 34: Type realType = GetRealType(entity); 35:  36: foreach (dynamic rule in (getRulesMethod.MakeGenericMethod(realType).Invoke(ruleset, null) as IEnumerable)) 37: { 38: if (rule.CanDelete(entity, ctx) == false) 39: { 40: throw (new Exception(String.Format("Cannot delete entity {0} due to rule {1}", entity, rule.Name))); 41: } 42: } 43: } 44:  45: foreach (ObjectStateEntry entry in octx.ObjectStateManager.GetObjectStateEntries(EntityState.Modified)) 46: { 47: Object entity = entry.Entity; 48: Type realType = GetRealType(entity); 49:  50: foreach (dynamic rule in (getRulesMethod.MakeGenericMethod(realType).Invoke(ruleset, null) as IEnumerable)) 51: { 52: if (rule.CanUpdate(entity, ctx) == false) 53: { 54: throw (new Exception(String.Format("Cannot update entity {0} due to rule {1}", entity, rule.Name))); 55: } 56: } 57: } 58: } 59:  60: public static IRuleset CreateRuleset(this DbContext context) 61: { 62: Tuple<IRuleset, DbContext> ruleset = null; 63: ObjectContext octx = (context as IObjectContextAdapter).ObjectContext; 64:  65: if (rulesets.TryGetValue(octx, out ruleset) == false) 66: { 67: ruleset = rulesets[octx] = new Tuple<IRuleset, DbContext>(new Ruleset(octx), context); 68: 69: octx.SavingChanges += OnSaving; 70: } 71:  72: return (ruleset.Item1); 73: } 74: } It relies on the SavingChanges event of the ObjectContext to intercept the saving operations before they are actually issued. Yes, it uses a bit of dynamic magic! Very handy, by the way! So, let’s put it all together: 1: using (MyContext ctx = new MyContext()) 2: { 3: IRuleset rules = ctx.CreateRuleset(); 4: rules.AddRule(new ProductRule()); 5:  6: ctx.Products.Add(new Product() { Name = "xyz", Price = 50000 }); 7:  8: ctx.SaveChanges(); //an exception is fired here 9:  10: //when we no longer need to apply the rules 11: rules.Dispose(); 12: } Feel free to use it and extend it any way you like, and do give me your feedback! As a final note, this can be easily changed to support plain old Entity Framework (not Code First, that is), if that is what you are using.

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  • OData &ndash; The easiest service I can create: now with updates

    - by Jon Dalberg
    The other day I created a simple NastyWord service exposed via OData. It was read-only and used an in-memory backing store for the words. Today I’ll modify it to use a file instead of a list and I’ll accept new nasty words by implementing IUpdatable directly. The first thing to do is enable the service to accept new entries. This is done at configuration time by adding the “WriteAppend” access rule: 1: public class NastyWords : DataService<NastyWordsDataSource> 2: { 3: // This method is called only once to initialize service-wide policies. 4: public static void InitializeService(DataServiceConfiguration config) 5: { 6: config.SetEntitySetAccessRule("*", EntitySetRights.AllRead | EntitySetRights.WriteAppend); 7: config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V2; 8: } 9: }   Next I placed a file, NastyWords.txt, in the “App_Data” folder and added a few *choice* words to start. This required one simple change to our NastyWordDataSource.cs file: 1: public NastyWordsDataSource() 2: { 3: UpdateFromSource(); 4: } 5:   6: private void UpdateFromSource() 7: { 8: var words = File.ReadAllLines(pathToFile); 9: NastyWords = (from w in words 10: select new NastyWord { Word = w }).AsQueryable(); 11: }   Nothing too shocking here, just reading each line from the NastyWords.txt file and exposing them. Next, I implemented IUpdatable which comes with a boat-load of methods. We don’t need all of them for now since we are only concerned with allowing new values. Here are the methods we must implement, all the others throw a NotImplementedException: 1: public object CreateResource(string containerName, string fullTypeName) 2: { 3: var nastyWord = new NastyWord(); 4: pendingUpdates.Add(nastyWord); 5: return nastyWord; 6: } 7:   8: public object ResolveResource(object resource) 9: { 10: return resource; 11: } 12:   13: public void SaveChanges() 14: { 15: var intersect = (from w in pendingUpdates 16: select w.Word).Intersect(from n in NastyWords 17: select n.Word); 18:   19: if (intersect.Count() > 0) 20: throw new DataServiceException(500, "duplicate entry"); 21:   22: var lines = from w in pendingUpdates 23: select w.Word; 24:   25: File.AppendAllLines(pathToFile, 26: lines, 27: Encoding.UTF8); 28:   29: pendingUpdates.Clear(); 30:   31: UpdateFromSource(); 32: } 33:   34: public void SetValue(object targetResource, string propertyName, object propertyValue) 35: { 36: targetResource.GetType().GetProperty(propertyName).SetValue(targetResource, propertyValue, null); 37: }   I use a simple list to contain the pending updates and only commit them when the “SaveChanges” method is called. Here’s the order these methods are called in our service during an insert: CreateResource – here we just instantiate a new NastyWord and stick a reference to it in our pending updates list. SetValue – this is where the “Word” property of the NastyWord instance is set. SaveChanges – get the list of pending updates, barfing on duplicates, write them to the file and clear our pending list. ResolveResource – the newly created resource will be returned directly here since we aren’t dealing with “handles” to objects but the actual objects themselves. Not too bad, eh? I didn’t find this documented anywhere but a little bit of digging in the OData spec and use of Fiddler made it pretty easy to figure out. Here is some client code which would add a new nasty word: 1: static void Main(string[] args) 2: { 3: var svc = new ServiceReference1.NastyWordsDataSource(new Uri("http://localhost.:60921/NastyWords.svc")); 4: svc.AddToNastyWords(new ServiceReference1.NastyWord() { Word = "shat" }); 5:   6: svc.SaveChanges(); 7: }   Here’s all of the code so far for to implement the service: 1: using System; 2: using System.Collections.Generic; 3: using System.Data.Services; 4: using System.Data.Services.Common; 5: using System.Linq; 6: using System.ServiceModel.Web; 7: using System.Web; 8: using System.IO; 9: using System.Text; 10:   11: namespace ONasty 12: { 13: [DataServiceKey("Word")] 14: public class NastyWord 15: { 16: public string Word { get; set; } 17: } 18:   19: public class NastyWordsDataSource : IUpdatable 20: { 21: private List<NastyWord> pendingUpdates = new List<NastyWord>(); 22: private string pathToFile = @"path to your\App_Data\NastyWords.txt"; 23:   24: public NastyWordsDataSource() 25: { 26: UpdateFromSource(); 27: } 28:   29: private void UpdateFromSource() 30: { 31: var words = File.ReadAllLines(pathToFile); 32: NastyWords = (from w in words 33: select new NastyWord { Word = w }).AsQueryable(); 34: } 35:   36: public IQueryable<NastyWord> NastyWords { get; private set; } 37:   38: public void AddReferenceToCollection(object targetResource, string propertyName, object resourceToBeAdded) 39: { 40: throw new NotImplementedException(); 41: } 42:   43: public void ClearChanges() 44: { 45: pendingUpdates.Clear(); 46: } 47:   48: public object CreateResource(string containerName, string fullTypeName) 49: { 50: var nastyWord = new NastyWord(); 51: pendingUpdates.Add(nastyWord); 52: return nastyWord; 53: } 54:   55: public void DeleteResource(object targetResource) 56: { 57: throw new NotImplementedException(); 58: } 59:   60: public object GetResource(IQueryable query, string fullTypeName) 61: { 62: throw new NotImplementedException(); 63: } 64:   65: public object GetValue(object targetResource, string propertyName) 66: { 67: throw new NotImplementedException(); 68: } 69:   70: public void RemoveReferenceFromCollection(object targetResource, string propertyName, object resourceToBeRemoved) 71: { 72: throw new NotImplementedException(); 73: } 74:   75: public object ResetResource(object resource) 76: { 77: throw new NotImplementedException(); 78: } 79:   80: public object ResolveResource(object resource) 81: { 82: return resource; 83: } 84:   85: public void SaveChanges() 86: { 87: var intersect = (from w in pendingUpdates 88: select w.Word).Intersect(from n in NastyWords 89: select n.Word); 90:   91: if (intersect.Count() > 0) 92: throw new DataServiceException(500, "duplicate entry"); 93:   94: var lines = from w in pendingUpdates 95: select w.Word; 96:   97: File.AppendAllLines(pathToFile, 98: lines, 99: Encoding.UTF8); 100:   101: pendingUpdates.Clear(); 102:   103: UpdateFromSource(); 104: } 105:   106: public void SetReference(object targetResource, string propertyName, object propertyValue) 107: { 108: throw new NotImplementedException(); 109: } 110:   111: public void SetValue(object targetResource, string propertyName, object propertyValue) 112: { 113: targetResource.GetType().GetProperty(propertyName).SetValue(targetResource, propertyValue, null); 114: } 115: } 116:   117: public class NastyWords : DataService<NastyWordsDataSource> 118: { 119: // This method is called only once to initialize service-wide policies. 120: public static void InitializeService(DataServiceConfiguration config) 121: { 122: config.SetEntitySetAccessRule("*", EntitySetRights.AllRead | EntitySetRights.WriteAppend); 123: config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V2; 124: } 125: } 126: } Next time we’ll allow removing nasty words. Enjoy!

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  • Hibernate/Spring: failed to lazily initialize - no session or session was closed

    - by Niko
    I know something similar has been asked already, but unfortunately I wasn't able to find a reliable answer - even with searching for over 2 days. The basic problem is the same as asked multiple time. I have a simple program with two POJOs Event and User - where a user can have multiple events. @Entity @Table public class Event { private Long id; private String name; private User user; @Column @Id @GeneratedValue public Long getId() {return id;} public void setId(Long id) { this.id = id; } @Column public String getName() {return name;} public void setName(String name) {this.name = name;} @ManyToOne @JoinColumn(name="user_id") public User getUser() {return user;} public void setUser(User user) {this.user = user;} } @Entity @Table public class User { private Long id; private String name; private List events; @Column @Id @GeneratedValue public Long getId() { return id; } public void setId(Long id) { this.id = id; } @Column public String getName() { return name; } public void setName(String name) { this.name = name; } @OneToMany(mappedBy="user", fetch=FetchType.LAZY) public List getEvents() { return events; } public void setEvents(List events) { this.events = events; } } Note: This is a sample project. I really want to use Lazy fetching here. I use spring and hibernate and have a simple basic-db.xml for loading: <?xml version="1.0" encoding="UTF-8"? <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd" <bean id="myDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close" scope="thread" <property name="driverClassName" value="com.mysql.jdbc.Driver" / <property name="url" value="jdbc:mysql://192.168.1.34:3306/hibernateTest" / <property name="username" value="root" / <property name="password" value="" / <aop:scoped-proxy/ </bean <bean class="org.springframework.beans.factory.config.CustomScopeConfigurer" <property name="scopes" <map <entry key="thread" <bean class="org.springframework.context.support.SimpleThreadScope" / </entry </map </property </bean <bean id="mySessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean" scope="thread" <property name="dataSource" ref="myDataSource" / <property name="annotatedClasses" <list <valuedata.model.User</value <valuedata.model.Event</value </list </property <property name="hibernateProperties" <props <prop key="hibernate.dialect"org.hibernate.dialect.MySQLDialect</prop <prop key="hibernate.show_sql"true</prop <prop key="hibernate.hbm2ddl.auto"create</prop </props </property <aop:scoped-proxy/ </bean <bean id="myUserDAO" class="data.dao.impl.UserDaoImpl" <property name="sessionFactory" ref="mySessionFactory" / </bean <bean id="myEventDAO" class="data.dao.impl.EventDaoImpl" <property name="sessionFactory" ref="mySessionFactory" / </bean </beans Note: I played around with the CustomScopeConfigurer and SimpleThreadScope, but that didnt change anything. I have a simple dao-impl (only pasting the userDao - the EventDao is pretty much the same - except with out the "listWith" function: public class UserDaoImpl implements UserDao{ private HibernateTemplate hibernateTemplate; public void setSessionFactory(SessionFactory sessionFactory) { this.hibernateTemplate = new HibernateTemplate(sessionFactory); } @SuppressWarnings("unchecked") @Override public List listUser() { return hibernateTemplate.find("from User"); } @Override public void saveUser(User user) { hibernateTemplate.saveOrUpdate(user); } @Override public List listUserWithEvent() { List users = hibernateTemplate.find("from User"); for (User user : users) { System.out.println("LIST : " + user.getName() + ":"); user.getEvents().size(); } return users; } } I am getting the org.hibernate.LazyInitializationException - failed to lazily initialize a collection of role: data.model.User.events, no session or session was closed at the line with user.getEvents().size(); And last but not least here is the Test class I use: public class HibernateTest { public static void main(String[] args) { ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("basic-db.xml"); UserDao udao = (UserDao) ac.getBean("myUserDAO"); EventDao edao = (EventDao) ac.getBean("myEventDAO"); System.out.println("New user..."); User user = new User(); user.setName("test"); Event event1 = new Event(); event1.setName("Birthday1"); event1.setUser(user); Event event2 = new Event(); event2.setName("Birthday2"); event2.setUser(user); udao.saveUser(user); edao.saveEvent(event1); edao.saveEvent(event2); List users = udao.listUserWithEvent(); System.out.println("Events for users"); for (User u : users) { System.out.println(u.getId() + ":" + u.getName() + " --"); for (Event e : u.getEvents()) { System.out.println("\t" + e.getId() + ":" + e.getName()); } } ((ConfigurableApplicationContext)ac).close(); } } and here is the Exception I get: 1621 [main] ERROR org.hibernate.LazyInitializationException - failed to lazily initialize a collection of role: data.model.User.events, no session or session was closed org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: data.model.User.events, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:380) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:372) at org.hibernate.collection.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:119) at org.hibernate.collection.PersistentBag.size(PersistentBag.java:248) at data.dao.impl.UserDaoImpl.listUserWithEvent(UserDaoImpl.java:38) at HibernateTest.main(HibernateTest.java:44) Exception in thread "main" org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: data.model.User.events, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:380) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:372) at org.hibernate.collection.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:119) at org.hibernate.collection.PersistentBag.size(PersistentBag.java:248) at data.dao.impl.UserDaoImpl.listUserWithEvent(UserDaoImpl.java:38) at HibernateTest.main(HibernateTest.java:44) Things I tried but did not work: assign a threadScope and using beanfactory (I used "request" or "thread" - no difference noticed): // scope stuff Scope threadScope = new SimpleThreadScope(); ConfigurableListableBeanFactory beanFactory = ac.getBeanFactory(); beanFactory.registerScope("request", threadScope); ac.refresh(); ... Setting up a transaction by getting the session object from the deo: ... Transaction tx = ((UserDaoImpl)udao).getSession().beginTransaction(); tx.begin(); users = udao.listUserWithEvent(); ... getting a transaction within the listUserWithEvent() public List listUserWithEvent() { SessionFactory sf = hibernateTemplate.getSessionFactory(); Session s = sf.openSession(); Transaction tx = s.beginTransaction(); tx.begin(); List users = hibernateTemplate.find("from User"); for (User user : users) { System.out.println("LIST : " + user.getName() + ":"); user.getEvents().size(); } tx.commit(); return users; } I am really out of ideas by now. Also, using the listUser or listEvent just work fine.

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  • Java: If vs. Switch

    - by _ande_turner_
    I have a piece of code with a) which I replaced with b) purely for legibility ... a) if ( WORD[ INDEX ] == 'A' ) branch = BRANCH.A; /* B through to Y */ if ( WORD[ INDEX ] == 'Z' ) branch = BRANCH.Z; b) switch ( WORD[ INDEX ] ) { case 'A' : branch = BRANCH.A; break; /* B through to Y */ case 'Z' : branch = BRANCH.Z; break; } ... will the switch version cascade through all the permutations or jump to a case ? EDIT: Some of the answers below regard alternative approaches to the approach above. I have included the following to provide context for its use. The reason I asked, the Question above, was because the speed of adding words empirically improved. This isn't production code by any means, and was hacked together quickly as a PoC. The following seems to be a confirmation of failure for a thought experiment. I may need a much bigger corpus of words than the one I am currently using though. The failure arises from the fact I did not account for the null references still requiring memory. ( doh ! ) public class Dictionary { private static Dictionary ROOT; private boolean terminus; private Dictionary A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z; private static Dictionary instantiate( final Dictionary DICTIONARY ) { return ( DICTIONARY == null ) ? new Dictionary() : DICTIONARY; } private Dictionary() { this.terminus = false; this.A = this.B = this.C = this.D = this.E = this.F = this.G = this.H = this.I = this.J = this.K = this.L = this.M = this.N = this.O = this.P = this.Q = this.R = this.S = this.T = this.U = this.V = this.W = this.X = this.Y = this.Z = null; } public static void add( final String...STRINGS ) { Dictionary.ROOT = Dictionary.instantiate( Dictionary.ROOT ); for ( final String STRING : STRINGS ) Dictionary.add( STRING.toUpperCase().toCharArray(), Dictionary.ROOT , 0, STRING.length() - 1 ); } private static void add( final char[] WORD, final Dictionary BRANCH, final int INDEX, final int INDEX_LIMIT ) { Dictionary branch = null; switch ( WORD[ INDEX ] ) { case 'A' : branch = BRANCH.A = Dictionary.instantiate( BRANCH.A ); break; case 'B' : branch = BRANCH.B = Dictionary.instantiate( BRANCH.B ); break; case 'C' : branch = BRANCH.C = Dictionary.instantiate( BRANCH.C ); break; case 'D' : branch = BRANCH.D = Dictionary.instantiate( BRANCH.D ); break; case 'E' : branch = BRANCH.E = Dictionary.instantiate( BRANCH.E ); break; case 'F' : branch = BRANCH.F = Dictionary.instantiate( BRANCH.F ); break; case 'G' : branch = BRANCH.G = Dictionary.instantiate( BRANCH.G ); break; case 'H' : branch = BRANCH.H = Dictionary.instantiate( BRANCH.H ); break; case 'I' : branch = BRANCH.I = Dictionary.instantiate( BRANCH.I ); break; case 'J' : branch = BRANCH.J = Dictionary.instantiate( BRANCH.J ); break; case 'K' : branch = BRANCH.K = Dictionary.instantiate( BRANCH.K ); break; case 'L' : branch = BRANCH.L = Dictionary.instantiate( BRANCH.L ); break; case 'M' : branch = BRANCH.M = Dictionary.instantiate( BRANCH.M ); break; case 'N' : branch = BRANCH.N = Dictionary.instantiate( BRANCH.N ); break; case 'O' : branch = BRANCH.O = Dictionary.instantiate( BRANCH.O ); break; case 'P' : branch = BRANCH.P = Dictionary.instantiate( BRANCH.P ); break; case 'Q' : branch = BRANCH.Q = Dictionary.instantiate( BRANCH.Q ); break; case 'R' : branch = BRANCH.R = Dictionary.instantiate( BRANCH.R ); break; case 'S' : branch = BRANCH.S = Dictionary.instantiate( BRANCH.S ); break; case 'T' : branch = BRANCH.T = Dictionary.instantiate( BRANCH.T ); break; case 'U' : branch = BRANCH.U = Dictionary.instantiate( BRANCH.U ); break; case 'V' : branch = BRANCH.V = Dictionary.instantiate( BRANCH.V ); break; case 'W' : branch = BRANCH.W = Dictionary.instantiate( BRANCH.W ); break; case 'X' : branch = BRANCH.X = Dictionary.instantiate( BRANCH.X ); break; case 'Y' : branch = BRANCH.Y = Dictionary.instantiate( BRANCH.Y ); break; case 'Z' : branch = BRANCH.Z = Dictionary.instantiate( BRANCH.Z ); break; } if ( INDEX == INDEX_LIMIT ) branch.terminus = true; else Dictionary.add( WORD, branch, INDEX + 1, INDEX_LIMIT ); } public static boolean is( final String STRING ) { Dictionary.ROOT = Dictionary.instantiate( Dictionary.ROOT ); return Dictionary.is( STRING.toUpperCase().toCharArray(), Dictionary.ROOT, 0, STRING.length() - 1 ); } private static boolean is( final char[] WORD, final Dictionary BRANCH, final int INDEX, final int INDEX_LIMIT ) { Dictionary branch = null; switch ( WORD[ INDEX ] ) { case 'A' : branch = BRANCH.A; break; case 'B' : branch = BRANCH.B; break; case 'C' : branch = BRANCH.C; break; case 'D' : branch = BRANCH.D; break; case 'E' : branch = BRANCH.E; break; case 'F' : branch = BRANCH.F; break; case 'G' : branch = BRANCH.G; break; case 'H' : branch = BRANCH.H; break; case 'I' : branch = BRANCH.I; break; case 'J' : branch = BRANCH.J; break; case 'K' : branch = BRANCH.K; break; case 'L' : branch = BRANCH.L; break; case 'M' : branch = BRANCH.M; break; case 'N' : branch = BRANCH.N; break; case 'O' : branch = BRANCH.O; break; case 'P' : branch = BRANCH.P; break; case 'Q' : branch = BRANCH.Q; break; case 'R' : branch = BRANCH.R; break; case 'S' : branch = BRANCH.S; break; case 'T' : branch = BRANCH.T; break; case 'U' : branch = BRANCH.U; break; case 'V' : branch = BRANCH.V; break; case 'W' : branch = BRANCH.W; break; case 'X' : branch = BRANCH.X; break; case 'Y' : branch = BRANCH.Y; break; case 'Z' : branch = BRANCH.Z; break; } if ( branch == null ) return false; if ( INDEX == INDEX_LIMIT ) return branch.terminus; else return Dictionary.is( WORD, branch, INDEX + 1, INDEX_LIMIT ); } }

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  • Array help Index out of range exeption was unhandled

    - by Michael Quiles
    I am trying to populate combo boxes from a text file using comma as a delimiter everything was working fine, but now when I debug I get the "Index out of range exeption was unhandled" warning. I guess I need a fresh pair of eyes to see where I went wrong, I commented on the line that gets the error //Fname = fields[1]; using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Drawing.Printing; using System.Linq; using System.Text; using System.Windows.Forms; using System.IO; namespace Sullivan_Payroll { public partial class xEmpForm : Form { bool complete = false; public xEmpForm() { InitializeComponent(); } private void xEmpForm_Resize(object sender, EventArgs e) { this.xCenterPanel.Left = Convert.ToInt16((this.Width - this.xCenterPanel.Width) / 2); this.xCenterPanel.Top = Convert.ToInt16((this.Height - this.xCenterPanel.Height) / 2); Refresh(); } private void exitToolStripMenuItem_Click(object sender, EventArgs e) { //Exits the application this.Close(); } private void xEmpForm_FormClosing(object sender, FormClosingEventArgs e) //use this on xtrip calculator { DialogResult Response; if (complete == true) { Application.Exit(); } else { Response = MessageBox.Show("Are you sure you want to Exit?", "Exit", MessageBoxButtons.YesNo, MessageBoxIcon.Question, MessageBoxDefaultButton.Button2); if (Response == DialogResult.No) { complete = false; e.Cancel = true; } else { complete = true; Application.Exit(); } } } private void xEmpForm_Load(object sender, EventArgs e) { //file sources string fileDept = "source\\Department.txt"; string fileSex = "source\\Sex.txt"; string fileStatus = "source\\Status.txt"; if (File.Exists(fileDept)) { using (System.IO.StreamReader sr = System.IO.File.OpenText(fileDept)) { string dept = ""; while ((dept = sr.ReadLine()) != null) { this.xDeptComboBox.Items.Add(dept); } } } else { MessageBox.Show("The Department file can not be found.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); } if (File.Exists(fileSex)) { using (System.IO.StreamReader sr = System.IO.File.OpenText(fileSex)) { string sex = ""; while ((sex = sr.ReadLine()) != null) { this.xSexComboBox.Items.Add(sex); } } } else { MessageBox.Show("The Sex file can not be found.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); } if (File.Exists(fileStatus)) { using (System.IO.StreamReader sr = System.IO.File.OpenText(fileStatus)) { string status = ""; while ((status = sr.ReadLine()) != null) { this.xStatusComboBox.Items.Add(status); } } } else { MessageBox.Show("The Status file can not be found.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); } } private void xFileSaveMenuItem_Click(object sender, EventArgs e) { { const string fileNew = "source\\New Staff.txt"; string recordIn; FileStream outFile = new FileStream(fileNew, FileMode.Create, FileAccess.Write); StreamWriter writer = new StreamWriter(outFile); for (int count = 0; count <= this.xEmployeeListBox.Items.Count - 1; count++) { this.xEmployeeListBox.SelectedIndex = count; recordIn = this.xEmployeeListBox.SelectedItem.ToString(); writer.WriteLine(recordIn); } writer.Close(); outFile.Close(); this.xDeptComboBox.SelectedIndex = -1; this.xStatusComboBox.SelectedIndex = -1; this.xSexComboBox.SelectedIndex = -1; MessageBox.Show("your file is saved"); } } private void xViewFacultyMenuItem_Click(object sender, EventArgs e) { const string fileStaff = "source\\Staff.txt"; const char DELIM = ','; string Lname, Fname, Depart, Stat, Sex, Salary, cDept, cStat, cSex; double Gtotal; string recordIn; string[] fields; cDept = this.xDeptComboBox.SelectedItem.ToString(); cStat = this.xStatusComboBox.SelectedItem.ToString(); cSex = this.xSexComboBox.SelectedItem.ToString(); FileStream inFile = new FileStream(fileStaff, FileMode.Open, FileAccess.Read); StreamReader reader = new StreamReader(inFile); recordIn = reader.ReadLine(); while (recordIn != null) { fields = recordIn.Split(DELIM); Lname = fields[0]; Fname = fields[1]; // this is where the error appears Depart = fields[2]; Stat = fields[3]; Sex = fields[4]; Salary = fields[5]; Fname = fields[1].TrimStart(null); Depart = fields[2].TrimStart(null); Stat = fields[3].TrimStart(null); Sex = fields[4].TrimStart(null); Salary = fields[5].TrimStart(null); Gtotal = double.Parse(Salary); if (Depart == cDept && cStat == Stat && cSex == Sex) { this.xEmployeeListBox.Items.Add(recordIn); } recordIn = reader.ReadLine(); } reader.Close(); inFile.Close(); if (this.xEmployeeListBox.Items.Count >= 1) { this.xFileSaveMenuItem.Enabled = true; this.xFilePrintMenuItem.Enabled = true; this.xEditClearMenuItem.Enabled = true; } else { this.xFileSaveMenuItem.Enabled = false; this.xFilePrintMenuItem.Enabled = false; this.xEditClearMenuItem.Enabled = false; MessageBox.Show("Records not found"); } } private void xEditClearMenuItem_Click(object sender, EventArgs e) { this.xEmployeeListBox.Items.Clear(); this.xDeptComboBox.SelectedIndex = -1; this.xStatusComboBox.SelectedIndex = -1; this.xSexComboBox.SelectedIndex = -1; this.xFileSaveMenuItem.Enabled = false; this.xFilePrintMenuItem.Enabled = false; this.xEditClearMenuItem.Enabled = false; } } } Source file -- Anderson, Kristen, Accounting, Assistant, Female, 43155 Ball, Robin, Accounting, Instructor, Female, 42723 Chin, Roger, Accounting, Full, Male,59281 Coats, William, Accounting, Assistant, Male, 45371 Doepke, Cheryl, Accounting, Full, Female, 52105 Downs, Clifton, Accounting, Associate, Male, 46887 Garafano, Karen, Finance, Associate, Female, 49000 Hill, Trevor, Management, Instructor, Male, 38590 Jackson, Carole, Accounting, Instructor, Female, 38781 Jacobson, Andrew, Management, Full, Male, 56281 Lewis, Karl, Management, Associate, Male, 48387 Mack, Kevin, Management, Assistant, Male, 45000 McKaye, Susan, Management, Instructor, Female, 43979 Nelsen, Beth, Finance, Full, Female, 52339 Nelson, Dale, Accounting, Full, Male, 54578 Palermo, Sheryl, Accounting, Associate, Female, 45617 Rais, Mary, Finance, Instructor, Female, 27000 Scheib, Earl, Management, Instructor, Male, 37389 Smith, Tom, Finance, Full, Male, 57167 Smythe, Janice, Management, Associate, Female, 46887 True, David, Accounting, Full, Male, 53181 Young, Jeff, Management, Assistant, Male, 43513

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