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• java web templates across multiple WAR files

  - by Casey

  I have a multi WAR web application that was designed badly. There is a single WAR that is responsible for handling some authorization against a database and defines a standard web page using a jsp taglib. The main WAR basically checks the privileges of the user and than based on that, displays links to the context path of the other deployed WARS. Each of the other deployed WARs includes this custom tag lib. I am working on redesigning this application, and one of the nice things that I want to retain is that we have other project teams that have developed these WAR modules that "plug into" our current system to take advantage of other things we have to offer. I am not entirely sure how to handle the page templates though. I need a templating system that would be easy enough to use across multiple wars (I was thinking of jsp fragments??). I really only need to define a consistent header and main navigation section. Whatever else is displayed on the page is up to the individual web project. Any suggestions? I hope that this is clear, if not I can elaborate more.

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• Can tomcat perform ssl redirection by filtering host alias?

  - by Stephen

  Hi, We have a tomcat server (6.0.20) running one web application behind two urls, e.g. www.foo and secure.foo This is configured in the server.xml as one host with a single alias: <Host name="www.foo" appBase="webapps"> <Context docBase="foo" path=""></Context> <Alias>secure.foo</Alias> </Host> Ideally we'd like any requests to secure.foo on port 80 to be automatically redirected to use ssl. However, I can only find instructions for redirecting based on the path after the hostname, so I could add a /* security constraint but then this would apply to both urls. Does anyone know if it's possible to apply the redirection by filtering on hostname requested? (We've already got the ssl connector, certificate, etc. working ok). I know we could do it by sticking an apache server in front of tomcat and handling the redirection there, but I'm curious to know if tomcat can do this on its own. Thanks

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• Linux apache developing configuration

  - by Jeffrey Vandenborne

  Recenly reinstalled my system, and came to a point where I need apache and php. I've been searching a long time, but I can't figure out how to configure apache the best way for a developer computer. The plan is simple, I want to install apache 2 + mysql server so I can develop some php website. I don't want to install lamp though, just the apache2, php5 and mysql. The problem that I've been looking an answer for is the permissions on the /var/www/ folder. I've tried making it my folder using the chown command, followed by a chmod -R 755 /var/www. Most things work then, but fwrite for example won't work, because I need to give write permissions to everyone, unless I change my global umask to 000 I'm not sure what I can do. In short: I want to install apache2, php5, mysql-server without using lamp, but configured in a way so I can open up netbeans, start a project with root in /var/www/, and run every single function without permission faults. Does anyone have experiences or workarounds to this? Extra: OS: Ubuntu 10.04 ARCH: x86_64

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• ASP.Net event only being raised every other time?

  - by eftpotrm

  I have an ASP.Net web user control which represents a single entry in a list. To allow users to reorder the items, each item has buttons to move the item up or down the list. Clicking on one of these raises an event to the parent page, which then shuffles the items in the placeholder control. Code fragments from the list entry: Public Event UpClicked As System.EventHandler Protected Sub btnUp_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnUp.Click RaiseEvent UpClicked(Me, New EventArgs()) End Sub And the parent container: rem (within the code to add an individual item to the placeholder) AddHandler l_oItem.UpClicked, AddressOf UpClicked Protected Sub UpClicked(ByVal sender As Object, ByVal e As EventArgs) MoveItem(DirectCast(sender, ScriptListItem), -1) End Sub It originally looked in testing like every other time the value for sender (verified by its properties) that reaches UpClicked is of an adjacent ListItem, not the one I've just clicked on - the first click is always wrong, then the second for the correct control. At present, testing appears to show that the button's click event is just being ignored every other time through. Breakpoints on the click events within the control simply aren't being hit, though the events are definitely being established. Why?

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• Javascript, IE, Strings, and Performance problems

  - by Infinity

  Hey guys, So we have this product, and it's really slow in IE. We've already applied a lot of the practices advised by the IE guys themselves (like this, and this), and try to sacrifice clean code for performance in the critical parts like DOM manipulation. However, as you can see in this IE profiler screenshot.. Just "String" is the biggest offender. Almost 750ms of exclusive time. Does this mean IE is spending 750ms just instantiating Strings? I also read this stuff on the Opera dev blog: A build script can remove whitespace, comments, replace strings with Array lookups (to avoid MSIE creating a string object for every single instance of a string — even in conditions) But no more info regarding this. Anyone can clarify? It seems like IE has to create a full String instance every time you have " " in your code, which could explain this, but I don't know what the array lookup optimization would look like. BTW- we don't really do much of string concatenation anywhere in the code. The library we use is MooTools 1.2.4 Any suggestions will be appreciated! Thx

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• SQL Compact performance on device

  - by Ben M

  My SQL Compact database is very simple, with just three tables and a single index on one of the tables (the table with 200k rows; the other two have less than a hundred each). The first time the .sdf file is used by my Compact Framework application on the target Windows Mobile device, the system hangs for well over a minute while "something" is done to the database: when deployed, the DB is 17 megabytes, and after this first usage, it balloons to 24 megs. All subsequent usage is pretty fast, so I'm assuming there's some sort of initialization / index building going on during this first usage. I'd rather not subject the user to this delay, so I'm wondering what this initialization process is and whether it can be performed before deployment. For now, I've copied the "initialized" database back to my desktop for use in the setup project, but I'd really like to have a better answer / solution. I've tried "full compact / repair" in the VS Database Properties dialog, but this made no difference. Any ideas? For the record, I should add that the database is only read from by the device application -- no modifications are made by that code.

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• Merge n files using a C program

  - by Amal

  I am writing a download Accelerator. So I download a file from the webserver into n parts. Now I want to merge the files into 1 single file. So I use the following code. And the file names are in the correct order. But the output file I am getting is different from the original download file. Can you tell me where could the error be ?C int cbd_merge_files(const char** filenames, int n, const char* final_filename) { FILE* fp = fopen(final_filename, "wb"); if (fp == NULL) return 1; char buffer[4097]; for (int i = 0; i < n; ++i) { const char* fname = filenames[i]; FILE* fp_read = fopen(fname, "rb"); if (fp_read == NULL) return 1; int n; while ((n = fread(buffer, sizeof(char), 4096, fp_read))) { int k = fwrite(buffer, sizeof(char), n, fp); if (!k) return 1; } fclose(fp_read); } fclose(fp); return 0; }

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• When using Direct3D, how much math is being done on the CPU?

  - by zirgen

  Context: I'm just starting out. I'm not even touching the Direct3D 11 API, and instead looking at understanding the pipeline, etc. From looking at documentation and information floating around the web, it seems like some calculations are being handled by the application. That, is, instead of simply presenting matrices to multiply to the GPU, the calculations are being done by a math library that operates on the CPU. I don't have any particular resources to point to, although I guess I can point to the XNA Math Library or the samples shipped in the February DX SDK. When you see code like mViewProj = mView * mProj;, that projection is being calculated on the CPU. Or am I wrong? If you were writing a program, where you can have 10 cubes on the screen, where you can move or rotate cubes, as well as viewpoint, what calculations would you do on the CPU? I think I would store the geometry for the a single cube, and then transform matrices representing the actual instances. And then it seems I would use the XNA math library, or another of my choosing, to transform each cube in model space. Then get the coordinates in world space. Then push the information to the GPU. That's quite a bit of calculation on the CPU. Am I wrong? Am I reaching conclusions based on too little information and understanding? What terms should I Google for, if the answer is STFW? Or if I am right, why aren't these calculations being pushed to the GPU as well?

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• How to differentiate between exceptions i can show the user, and ones i can't?

  - by Ian Boyd

  i have some business logic that traps some logically invalid situations, e.g. trying to reverse a transaction that was already reversed. In this case the correct action is to inform the user: Transaction already reversed or Cannot reverse a reversing transaction or You do not have permission to reverse transactions or This transaction is on a session that has already been closed or This transaction is too old to be reversed The question is, how do i communicate these exceptional cases back to the calling code, so they can show the user? Do i create a separate exception for each case: catch (ETransactionAlreadyReversedException) MessageBox.Show('Transaction already reversed') catch (EReversingAReversingTransactionException) MessageBox.Show('Cannot reverse a reversing transaction') catch (ENoPermissionToReverseTranasctionException) MessageBox.Show('You do not have permission to reverse transactions') catch (ECannotReverseTransactionOnAlredyClosedSessionException) MessageBox.Show('This transaction is on a session that has already been closed') catch (ECannotReverseTooOldTransactionException) MessageBox.Show('This transaction is too old to be reversed') Downside for this is that when there's a new logical case to show the user: Tranasctions created by NSL cannot be reversed i don't simply show the user a message, and instead it leaks out as an unhandled excpetion, when really it should be handled with another MessageBox. The alternative is to create a single exception class: `EReverseTransactionException` With the understanding that any exception of this type is a logical check, that should be handled with a message box: catch (EReverseTransactionException) But it's still understood that any other exceptions, ones that involve, for example, an memory ECC parity error, continue unhandled. In other words, i don't convert all errors that can be thrown by the ReverseTransaction() method into EReverseTransactionException, only ones that are logically invalid cause of the user.

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• Does Interlocked guarantee visibility to other threads in C# or do I still have to use volatile?

  - by Lirik

  I've been reading the answer to a similar question, but I'm still a little confused... Abel had a great answer, but this is the part that I'm unsure about: ...declaring a variable volatile makes it volatile for every single access. It is impossible to force this behavior any other way, hence volatile cannot be replaced with Interlocked. This is needed in scenarios where other libraries, interfaces or hardware can access your variable and update it anytime, or need the most recent version. Does Interlocked guarantee visibility of the atomic operation to all threads, or do I still have to use the volatile keyword on the value in order to guarantee visibility of the change? Here is my example: public class CountDownLatch { private volatile int m_remain; // <--- do I need the volatile keyword there since I'm using Interlocked? private EventWaitHandle m_event; public CountDownLatch (int count) { Reset(count); } public void Reset(int count) { if (count < 0) throw new ArgumentOutOfRangeException(); m_remain = count; m_event = new ManualResetEvent(false); if (m_remain == 0) { m_event.Set(); } } public void Signal() { // The last thread to signal also sets the event. if (Interlocked.Decrement(ref m_remain) == 0) m_event.Set(); } public void Wait() { m_event.WaitOne(); } }

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• WPF Event Handler in Another Class

  - by Nathan Tornquist

  I have built a series of event handlers for some custom WPF controls. The event handles format the text displayed when the user enters or leaves a textbox based on the type of data contained (Phone number, zip code, monetary value, etc.) Right now I have all of the events locally in the C# code directly attached to the xaml. Because I have developed a could controls, this means that the logic is repeated a lot, and if I want to change the program-wide functionality I would have to make changes everywhere the event code is located. I am sure there is a way to put all of my event handlers in a single class. Can anyone help point me in the correct direction? I saw this article: Event Handler located in different class than MainWindow But I'm not sure if it directly relates to what I'm doing. I would rather make small changes to the existing logic that I have, as it works, then rewrite everything into commands. I would essentially like to something like this if possible: LostFocus="ExpandedTextBoxEvents.TextBox_LostFocus" It is easy enough to do something like this: private void TextBoxCurrencyGotFocus(object sender, RoutedEventArgs e) { ExpandedTextBoxEvents.TextBoxCurrencyGotFocus(sender, e); } private void TextBoxCurrencyLostFocus(object sender, RoutedEventArgs e) { ExpandedTextBoxEvents.TextBoxCurrencyLostFocus(sender, e); } But that is less elegant.

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• Defining and using controller methods in ember.js

  - by OriginalEXE

  first of all, I am total noob when it comes to OOP in JS, this is new to me so treat me like a noob. I am building my first ember.js application and I am stuck (not the first time but I would get unstuck by myself, this is a tough one though). I have two models: forms entries Entries is of course in (one to many) relationship to forms, so each form can have as many properties. Form properties: id : DS.attr( 'number' ), title : DS.attr( 'string' ), views : DS.attr( 'number' ), conversion : DS.attr( 'number' ), entries : DS.hasMany( 'entry' ) Entry properties: id : DS.attr( 'number' ), parent_id: DS.belongsTo( 'form' ) Now, I have forms route that displays all forms in tabled view, and each table row has some info like form id, name etc. and that works great. What I wanted to do is display the number of entries each form has. I figured I should do that via controller, so here is my controller now: // Form controller App.FormController = Ember.ObjectController.extend({ entriescount: function() { var entries = this.get( 'store').find( 'entry' ); return entries.filterBy( 'parent_id', this.get( 'id' ) ).get( 'length' ); }.property( '[email protected]_id') }); Now for some reason, when I use {{entriescount}} in {{#each}} loop, this returns nothing. It also returns nothing in single form route. Note that in both cases, {{title}} for example works. I am wondering, am I going the right way by using controller for this, and how do I get controller to output the data. Thanks

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• Why Is Apache Giving 403?

  - by ThinkCL

  I am getting 403 Errors from Apache when I send too many, 12, synchronous HTTP Posts via a desktop app I am building in XCode / Objective-C. The 12 POST requests are just a few kb each and go out instantly one after the other and the Apache Error Log shows... client denied by server configuration: /the-path/the-file.php Apache 2.0 PHP 5 and I have this same setup working fine on my local machine. The error is coming from a VPS with my host, which runs very fast and smooth and has plenty of resources. To debug I threw a sleep(1); function (stalls script execution by 1 second) into the php file and that fixed it. This makes me think that I am breaking some limit for too many requests for a single IP in a certain amount of time. I have googled and combed PHP ini and Apache configs, but I cannot find what that directive/setting might be. I should mention that the although it varies the first 4 or 5 POSTS usually work then it starts returning the 403 error intermittently after that. Just really acting like its bogging down. Any ideas?

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• Who needs singletons?

  - by sexyprout

  Imagine you access your MySQL database via PDO. You got some functions, and in these functions, you need to access the database. The first thing I thought of is global, like: $db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'root', 'pwd'); function some_function() { global $db; $db->query('...'); } But it's considered as a bad practice. So, after a little search, I ended up with the Singleton pattern, which "applies to situations in which there needs to be a single instance of a class." According to the example of the manual, we should do this: class Database { private static $instance, $db; private function __construct(){} static function singleton() { if(!isset(self::$instance)) self::$instance = new __CLASS__; return self:$instance; } function get() { if(!isset(self::$db)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd') return self::$db; } } function some_function() { $db = Database::singleton(); $db->get()->query('...'); } some_function(); But I just can't understand why you need that big class when you can do it merely with: class Database { private static $db; private function __construct(){} static function get() { if(!isset(self::$rand)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd'); return self::$db; } } function some_function() { Database::get()->query('...'); } some_function(); This last one works perfectly and I don't need to worry about $db anymore. But maybe I'm forgetting something. So, who's wrong, who's right?

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• Modeling many-to-one with constraints?

  - by Greg Beech

  I'm attempting to create a database model for movie classifications, where each movie could have a single classification from each of one of multiple rating systems (e.g. BBFC, MPAA). This is the current design, with all implied PKs and FKs: TABLE Movie ( MovieId INT ) TABLE ClassificationSystem ( ClassificationSystemId TINYINT ) TABLE Classification ( ClassificationId INT, ClassificationSystemId TINYINT ) TABLE MovieClassification ( MovieId INT, ClassificationId INT, Advice NVARCHAR(250) -- description of why the classification was given ) The problem is with the MovieClassification table whose constraints would allow multiple classifications from the same system, whereas it should ideally only permit either zero or one classifications from a given system. Is there any reasonable way to restructure this so that a movie having exactly zero or one classifications from any given system is enforced by database constraints, given the following requirements? Do not duplicate information that could be looked up (i.e. duplicating ClassificationSystemId in the MovieClassification table is not a good solution because this could get out of sync with the value in the Classification table) Remain extensible to multiple classification systems (i.e. a new classification system does not require any changes to the table structure)? Note also the Advice column - each mapping of a movie to a classification needs to have a textual description of why that classification was given to that movie. Any design would need to support this.

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• Understanding C++ pointers (when they point to a pointer)

  - by Stephano

  I think I understand references and pointers pretty well. Here is what I (think I) know: int i = 5; //i is a primitive type, the value is 5, i do not know the address. int *ptr; //a pointer to an int. i have no way if knowing the value yet. ptr = &i; //now i have an address for the value of i (called ptr) *ptr = 10; //go get the value stored at ptr and change it to 10 Please feel free to comment or correct these statements. Now I'm trying to make the jump to arrays of pointers. Here is what I do not know: char **char_ptrs = new char *[50]; Node **node_ptrs = new Node *[50]; My understanding is that I have 2 arrays of pointers, one set of pointers to chars and one to nodes. So if I wanted to set the values, I would do something like this: char_ptrs[0] = new char[20]; node_ptrs[0] = new Node; Now I have a pointer, in the 0 position of my array, in each respective array. Again, feel free to comment here if I'm confused. So, what does the ** operator do? Likewise, what is putting a single * next to the instantiation doing (*[50])? (what is that called exactly, instantiation?)

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• How to Bind a Command in WPF

  - by MegaMind

  Sometimes we used complex ways so many times, we forgot the simplest ways to do the task. I know how to do command binding, but i always use same approach. Create a class that implements ICommand interface and from the view model i create new instance of that class and binding works like a charm. This is the code that i used for command binding public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); DataContext = this; testCommand = new MeCommand(processor); } ICommand testCommand; public ICommand test { get { return testCommand; } } public void processor() { MessageBox.Show("hello world"); } } public class MeCommand : ICommand { public delegate void ExecuteMethod(); private ExecuteMethod meth; public MeCommand(ExecuteMethod exec) { meth = exec; } public bool CanExecute(object parameter) { return false; } public event EventHandler CanExecuteChanged; public void Execute(object parameter) { meth(); } } But i want to know the basic way to do this, no third party dll no new class creation. Do this simple command binding using a single class. Actual class implements from ICommand interface and do the work.

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• Using an initializer_list on a map of vectors

  - by Hooked

  I've been trying to initialize a map of <ints, vector<ints> > using the new 0X standard, but I cannot seem to get the syntax correct. I'd like to make a map with a single entry with key:value = 1:<3,4 #include <initializer_list> #include <map> #include <vector> using namespace std; map<int, vector<int> > A = {1,{3,4}}; .... It dies with the following error using gcc 4.4.3: error: no matching function for call to std::map<int,std::vector<int,std::allocator<int> >,std::less<int>,std::allocator<std::pair<const int,std::vector<int,std::allocator<int> > > > >::map(<brace-enclosed initializer list>) Edit Following the suggestion by Cogwheel and adding the extra brace it now compiles with a warning that can be gotten rid of using the -fno-deduce-init-list flag. Is there any danger in doing so?

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• Multiple "ObjectChangeTracker" getting created, can it be avoided?

  - by user555937

  Hi, We are working on a POC where we have following architecture (MVVM), WPF(Client) + WCF + Model(DataAccess)+ ADO.Net Entity Framework 4.0 (with SQL Server 2008 R2 as DB) All are different projects. In the DataAccess layer we have created different Entity Models(edmx) based on the functionality. The tables under perticular flow are grouped and created different entity models. We are using self tracking entities to and fro to communicate with the WPF client through wcf service. For Single model everything works fine. But when we created a Multiple models then few issues started coming. Mutliple models have few duplicate tables/entities. Two probels are, 1) When we try to access entities from different models mutiple objects "ObjectChangeTracker" are getting created. E.g. CompanyModel(edmx) - Company(Entity) - ObjectChangeTracker, ObjectState ProductModel(edmx) - Customer(Entity) - ObjectChangeTracker1, ObjectState1 OrderModel(edmx) - Oder(Entity) - ObjectChangeTracker2, ObjectState2 Is there any way to avoid this? 2) There are few tables which shared across the Models, E.g. Company(Entity) is used in All above mdoels. During compile time it does not thow any error. But run time It gives error saying "Schema specified is not valid. Errors: The mapping of CLR type to EDM type is ambiguous because multiple CLR types match the EDM type "Company"".. To resolve this, we renamed the entities with some prefix to make them Unique. Is there any other way we can resolve this without changing the name of the entity in the same assembly? Thanks in advance and appreciate if anyone has approach for these issues. Thanks, Kiran

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• Best (Java) book for understanding 'under the bonnet' for programming?

  - by Ben

  What would you say is the best book to buy to understand exactly how programming works under the hood in order to increase performance? I've coded in assembly at university, I studied computer architecture and I obviously did high level programming, but what I really dont understand is things like: -what is happening when I perform a cast -whats the difference in performance if I declare something global as opposed to local? -How does the memory layout for an ArrayList compare with a Vector or LinkedList? -Whats the overhead with pointers? -Are locks more efficient than using synchronized? -Would creating my own array using int[] be faster than using ArrayList -Advantages/disadvantages of declaring a variable volatile I have got a copy of Java Performance Tuning but it doesnt go down very low and it contains rather obvious things like suggesting a hashmap instead of using an ArrayList as you can map the keys to memory addresses etc. I want something a bit more Computer Sciencey, linking the programming language to what happens with the assembler/hardware. The reason im asking is that I have an interview coming up for a job in High Frequency Trading and everything has to be as efficient as possible, yet I cant remember every single possible efficiency saving so i'd just like to learn the fundamentals. Thanks in advance

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• Why would using a Temp table be faster than a nested query?

  - by Mongus Pong

  We are trying to optimise some of our queries. One query is doing the following: SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, INTO [#Gadget] FROM task t SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) as Client FROM [#Gadget] order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC DROP TABLE [#Gadget] (I have removed the complex subquery, cos I dont think its relevant other than to explain why this query has been done as a two stage process.) Now I would have thought it would be far more efficient to merge this down into a single query using subqueries as : SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) FROM ( SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, FROM task t ) as sub order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC This would give the optimiser better information to work out what was going on and avoid any temporary tables. It should be faster. But it turns out it is a lot slower. 8 seconds vs under 5 seconds. I cant work out why this would be the case as all my knowledge of databases imply that subqueries would always be faster than using temporary tables. Can anyone explain what could be going on!?!?

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• Are there any NOSQL-compatible CMS projects?

  - by Michael

  This question is partially related to an older question (Any CMS is Google App Engine compatible?) , but is slightly more general. It seems that in most CMS systems, the most fragile failure point is the database. Traditional database implementations scale poorly and will never be able to handle unforeseen spikes of traffic. Since Google App Engine was designed to help even small businesses overcome that problem, I had the same question that was asked earlier this year with less than satisfactory answers. But more generally, where are the CMS projects that support NOSQL databases? Looking over Wikipedia's list of CMS platforms, I see without much effort that only traditional RDBMS are supported by every single vendor on the list. I would have expected to see at least one or two projects handling CouchDB or similar engines. I understand the complexities of implementing a NOSQL solution to a problem that is typically solved using the relations cleanly expressed in any RDBMS, but there seems to be a rather wide market gap. Since databases are, today, easily outsourced to Google, Amazon, and others which use NOSQL models, I am amazed that there are not more projects actively pursuing this path. Am I simply not aware? Can someone please point me to projects that have real momentum that are developing on this path? I'm looking for two things: a CMS that has as its backbone a NOSQL database enabling easy database outsourcing (hosted MySQL clusters and similar solutions are not what I'm looking for) a project that is built to run on either a PaaS architecture like Google App Engine or an IaaS architecture like Amazon EC2 Any pointers in that direction would be most welcome.

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• JAR files, don't they just bloat and slow Java down?

  - by Josamoto

  Okay, the question might seem dumb, but I'm asking it anyways. After struggling for hours to get a Spring + BlazeDS project up and running, I discovered that I was having problems with my project as a result of not including the right dependencies for Spring etc. There were .jars missing from my WEB-INF/lib folder, yes, silly me. After a while, I managed to get all the .jar files where they belong, and it comes at a whopping 12.5MB at that, and there's more than 30 of them! Which concerns me, but it probably and hopefully shouldn't be concerned. How does Java operate in terms of these JAR files, they do take up quite a bit of hard drive space, taking into account that it's compressed and compiled source code. So that can really quickly populate a lot of RAM and in an instant. My questions are: Does Java load an entire .jar file into memory when say for instance a class in that .jar is instantiated? What about stuff that's in the .jar that never gets used. Do .jars get cached somehow, for optimized application performance? When a single .jar is loaded, I understand that the thing sits in memory and is available across multiple HTTP requests (i.e. for the lifetime of the server instance running), unlike PHP where objects are created on the fly with each request, is this assumption correct? When using Spring, I'm thinking, I had to include all those fiddly .jars, wouldn't I just be better off just using native Java, with say at least and ORM solution like Hibernate? So far, Spring just took extra time configuring, extra hard drive space, extra memory, cpu consumption, so I'm concerned that the framework is going to cost too much application performance just to get for example, IoC implemented with my BlazeDS server. There still has to come ORM, a unit testing framework and bits and pieces here and there. It's just so easy to bloat up a project quickly and irresponsibly easily. Where do I draw the line?

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• Concrete examples of state sharing between multiple viewmodels (WPF MVVM)

  - by JohnMetta

  I have a WPF/Entity Framework (4.0) project with many objects. I'd like to build the application so that that I can have object selection state shared across viewmodels. For Example: We have Cars, Drivers, Passengers, and Cargo classes. We also have UserControls for CarList, DriverList, etc. and editor windows for CarEditor, DriverEditor, etc. Furthermore, we have viewmodels for all of these (CarListViewModel, DriverListViewModel, CargoEditorViewModel, etc). This all composes a dockable interface where the user can have multiple object lists, editors, and viewers open. What I want is a concrete code example of how to wireup multiple viewmodels so that selecting a car in the CarList will cause that car to go live in the CarEditorView, but also be selected in any other view for which the context is valid (such as a DriverByCarView- or just DriverList if there is a filter predicate). There are a number of suggestions and discussions based on this question. The two methods that seem to dominate are: 3018307: Discusses state sharing by mentioning a messaging subsystem 1159035: Discusses state sharing by using an enclosing viewmodel Is one of these approaches better than the other? Does anyone have a concrete example of either/both of these methods in the form of a write-up or small code project? I'm still learning WPF, so pointers to entry points for reading API fundamentals are appreciated, but looking at code examples is where I usually go. Thanks In case anyone is interested, here are some other similar discussions: 3816961: Discusses returning multiple viewmodels depending on object type (i.e. a collection of arbitrary types adhering to a specific interface) 1928130: Discusses whether it is a good idea to aggregate viewmodels as properties of other viewmodels (e.g. a MainWindow viewmodel composed of panel viewmodels) 1120061: Essentially discusses whether to have use a viewmodel-per-model strategy or a viewmodel-per-view-element strategy. 4244222: Discusses whether or not to nest the viewmodels when using a nested object hierarchy. 4429708: Discusses sharing collections between viewmodels directly, but doesn't go into detail. List item: Discusses managing multiple selections within a single viewmodel.

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• Esper generating episodes

  - by Jasonojh

  I would like to use Esper to generate episodes of events. I am trying to detect the changes in robot movement during each time period and was wondering what would be the best way of implementation. The rules for generation of episodes from the events would be If the new event time(eg. 7sec, robot A) of a robot is more than 3 sec than the latest event(eg. 3 sec, robot A) of the same robot, the new event belongs to a new episode. Each episode should represent only one robot (eg. 2sec, robotA and 3sec, robotB should output 2 episodes) Input data: Event Time Robot Position 1 1 A 0 2 2 A 1 3 6 A 2 Output data should be: Array[0]={Event 1,Event 2} Array[1]={Event 3} //more than 3 sec Input data: Event Time Robot Position 1 1 A 0 2 2 A 1 3 4 B 0 4 6 A 2 Output data should be: Array[0]={Event 1,Event 2} Array[1]={Event 3} //different robot Array[2]={Event 4} Please help provide suggestions. I have tried using mulitple listeners, one for each robot, to create episodes and it works but I am trying to use a single EPL statement to do it. I have tried win:time_accum(3sec) group by robot but the second example output: Array[0]={Event 1,Event 2, Event 4} Array[1]={Event 3} as the time window is shifted everytime an event comes in, the system still thinks that event 4 is less than 3 sec due to event 3. how do I create a unique time window for each robot? Thank you for your suggestions and any help is greatly appreciated.

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