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  • Communication between layers in an application

    - by Petar Minchev
    Hi guys! Let's assume we have the following method in the business layer. What's the best practice to tell the UI layer that something went wrong and give also the error message? Should the method return an empty String when it was OK, otherwise the error message, or should it throw another exception in the catch code wrapping the caught exception? If we choose the second variant then the UI should have another try,catch which is too much try,catch maybe. Here is a pseudocode for the first variant. public String updateSomething() { try { //Begin transaction here dataLayer.do1(); dataLayer.do2(); dataLayer.doN(); } catch(Exception exc) { //Rollback transaction code here return exc.message; } return ""; } Is this a good practice or should I throw another exception in the catch(then the method will be void)?

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  • ASP.NET: How can I properly redirect requests with 404 errors?

    - by Adrian Grigore
    Hi, I'd like my ASP.NET MVC application to redirect failed requests to matching action methods of a certain controller. This works fine on my development machine running Windows 7, but not on my production machine running Windows 2008 R2. I set up my web.config as follows: <customErrors mode="On" defaultRedirect="/Error/ServerError/500"> <error statusCode="403" redirect="/Error/AccessDenied" /> <error statusCode="404" redirect="/Error/FileNotFound" /> </customErrors> This customErrors section works fine on both of my machines (production and development) for 500 Internal Server errors. It also works fine for 404 errors on my development machine. However, it does not properly redirect 404 errors on the production machine. Instead of /Error/FileNotFound, I get the standard 404 page that comes with IIS 7. What could be the problem here?

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  • error handling strategies in C?

    - by Leo
    Given the code below: typedef struct {int a;} test_t; arbitrary_t test_dosomething(test_t* test) { if (test == NULL) { //options: //1. print an error and let it crash //e.g. fprintf(stderr, "null ref at %s:%u", __FILE__, __LINE__); //2. stop the world //e.g. exit(1); //3. return (i.e. function does nothing) //4. attempt to re-init test } printf("%d", test->a); //do something w/ test } I want to get a compiler error if test is ever NULL, but I guess that's not possible in C. Since I need to do null checking at runtime, what option is the most proper way to handle it?

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  • Detecting GWT RichTextArea 'dirty' state

    - by David
    I want to detect when the contents of my GWT RichTextArea become 'dirty' (have been changed by the user) in order to enable a 'save' button accordingly. I suppose I could listen for key presses that are likely to have changed the contents; but browser support for key presses is notoriously quirky. I suppose I could, before editing begins, save the original contents in a variable, and upon key press, compare the current contents against that variable, but doing that on each key press is going to be really slow. Is there some neat way to achieve RichTextArea dirty-detection?

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  • How to catch this type of exceptions ?

    - by Lukas Šalkauskas
    I'm starting getting tired of this exception. Can't handle it, even so I'm using this: AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(CurrentDomain_UnhandledException); Still no success, Can anyone explain me, how I should handle it in a nice way. Or how to detect that it have fired this message and close the application, because I'm starting it automatically everytime it closes.

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  • Handling input from a keyboard wedge

    - by JDibble
    Following on from the question asked by Mykroft Best way to handle input from a keyboard “wedge” http://stackoverflow.com/questions/42437/best-way-to-handle-input-from-a-keyboard-wedge. I need to write a class that intercepts key strokes, if the input is determined to be from the keyboard wedge (as described in the above post) the data will be directed to POS classes to handle, otherwise they keystrokes must be passed on to be handled in windows in the normal manner. This raises two questions How can I intercept key strokes when not in a WinForm. How can I pass on the keypresses to windows. Thanks JDibble

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  • How should I handle the case in which a username is already in use?

    - by idealmachine
    I'm a JavaScript programmer and new to PHP and MySQL (want to get into server-side coding). Because I'm trying to learn PHP by building a simple online game (more specifically, correspondence chess), I'm starting by implementing a simple user accounts system. Of course, user registration comes first. What are the best practices for: How I should handle the (likely) possibility that when a user tries to register, the username he has chosen is already in use, particularly when it comes to function return values?($result === true is rather ugly, and I'm not sure whether checking the MySQL error code is the best way to do it either) How to cleanly handle varying page titles?($gPageTitle = '...'; require_once 'bgsheader.php'; is also rather ugly) Anything else I'm doing wrong? In some ways, PHP is rather different from JavaScript... Here is a (rather large) excerpt of the code I have written so far. Note that this is a work in progress and is missing security checks that I will add as my next step. function addUser( $username, $password ) { global $gDB, $gPasswordSalt; $stmt = $gDB->prepare( 'INSERT INTO user(user_name, user_password, user_registration) VALUES(?, ?, NOW())' ); $stmt || trigger_error( 'Failed to prepare statement: ' . htmlspecialchars( $gDB->error ) ); $hashedPassword = hash_hmac( 'sha256', $password, $gPasswordSalt, true ); $stmt->bind_param( 'ss', $username, $hashedPassword ); if( $stmt->execute() ) { return true; } elseif( $stmt->errno == 1062) { return 'exists'; } else { trigger_error( 'Failed to execute statement: ' . htmlspecialchars( $stmt->error ) ); } } $username = $_REQUEST['username']; $password = $_REQUEST['password']; $result = addUser( $username, $password ); if( $result === true ) { $gPageTitle = 'Registration successful'; require_once 'bgsheader.php'; echo '<p>You have successfully registered as ' . htmlspecialchars( $username ) . ' on this site.</p>'; } elseif( $result == 'exists' ) { $gPageTitle = 'Username already taken'; require_once 'bgsheader.php'; echo '<p>Someone is already using the username you have chosen. Please try using another one instead.'; } else { trigger_error('This should never happen'); } require_once 'bgsfooter.php';

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  • Javascript handling textarea

    - by bbenton
    Hi all, I'm a bit new to Javascript and am trying to create a delimited string from a textare. The problem is when passing in the textarea, it adds newlines for each row on the textarea. I need to have the entire textarea parsed into a string with a delimiter for each line (replacing the newline char). So for example, if you passed in a textarea with the following lines (which is also how it looks when using the alert function): abcd efgh ijkl It would look like: abcd-efgh-ijkl after parsing. function submitToForm(form) { var param_textarea = form.listofplugins.value; var test = param_textarea.replace(/\\r?\\n/, /:/) alert(test); } Thanks a lot!

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  • Handling Session ID with Spring

    - by Max
    Hi, I'm trying to build a Spring server for GWT (you can think of it as of Javascript AJAX client). But I can't decide on one point of architecture. How should session be created and used? The obvious easiest way - is to use HTTP sessions (cookies and stuff). Looks fine, but I think that sending session ID separate from the headers would be better (SOAP style). So, what is better: getMyPetsName(String sessionID, int petID) or getMyPetsName(int petID) + session ID through HTTP header (cookies or something). Another question is, if I use the first way (which I like more) - how do I handle session in Spring? I'm really newbie in Spring, and googling did not help. What I mean is: String getMyPetsName(String sessionID, int petID) { Session s = someWayToGetItById(sessionID); } Thanks in advance.

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  • Why use event listeners over function calls?

    - by Organiccat
    I've been studying event listeners lately and I think I've finally gotten them down. Basically, they are functions that are called on another object's method. My question is, why create an event listener when calling the function will work just fine? Example, I want to call player.display_health(), and when this is fired, the method player.get_health() should be fired and stored so that display_health() has access to it. Why should I use an event listener over simply calling the function? Even if display_health() were in another object, this still doesn't appear to be a problem to me. If you have another example that fits the usage better, please let me know. Perhaps particular languages don't benefit from it as much? (Javascript, PHP, ASP?)

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  • Server.TransferRequest returns blank page on specific server

    - by jishi
    I'm facing an issue that seems to be related to configuration. I have a webapplication based on MonoRail, where we utilize the routing feature from MonoRail. On the first request after the application has started, the routing isn't initialized. To circumvent this, I have the following code in Application_OnError(): public virtual void Application_OnError() { if ( // identified as routing error ) Server.TransferRequest( Context.Request.RawUrl, false ); return; } Problem beeing that on our development server (which runs server 2008 R2, with IIS 7.5 and .NET 3.5) returns a blank page without headers, but on my workstation (which runs win7, IIS 7.5 and .NET 3.5) it works fine. What could be the cause of this? If the code in Application_OnError() throws an exception, what would be the expected output? I have verified the following: The access-log shows one entry, I'm not sure if a TransferRequest would show up as a second entry when invoked successfully The application actually do some work according to my internal logs, and it doesn't die since a subsequent requests works flawlessly (because routing will be active) Any hints on what to look for would be greatly appreciated!

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  • C++ visitor pattern handling templated string types?

    - by Steve the Plant
    I'm trying to use the visitor pattern to serialize the contents of objects. However one snag I'm hitting is when I'm visiting strings. My strings are of a templated type, similar to STL's basic_string. So something like: basic_string<char_type, memory_allocator, other_possible_stuff> \\ many variations possible! Since I can have very many different templated string types, I can't go and add them to my visitor interface. It would be ridiculous. But I can't add templates to my VisitString method because C++ prevents using templates parameters in virtual methods. So what are my options to work around this?

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  • Umbraco: Handling In Page Javascript in Uswe Controls

    - by Burt
    I have quite a number of user controls that I need to embed in Umbraco macros. Each user control has quite a bit of in page javascript that needs loaded into the page. I have been building up the javascript with StringBuilder.Appendline then registering a startup script with code behind but this stinks and I feel there has to be a better way of going about this. Has anyone any ideas please? Thanks, B

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  • Doubt with c# handlers?

    - by aF
    I have this code in c# public void startRecognition(string pName) { presentationName = pName; if (WaveNative.waveInGetNumDevs() > 0) { string grammar = System.Environment.GetEnvironmentVariable("PUBLIC") + "\\SoundLog\\Presentations\\" + presentationName + "\\SpeechRecognition\\soundlog.cfg"; /* if (File.Exists(grammar)) { File.Delete(grammar); } executeCommand();*/ recContext = new SpSharedRecoContextClass(); recContext.CreateGrammar(0, out recGrammar); if (File.Exists(grammar)) { recGrammar.LoadCmdFromFile(grammar, SPLOADOPTIONS.SPLO_STATIC); recGrammar.SetGrammarState(SPGRAMMARSTATE.SPGS_ENABLED); recGrammar.SetRuleIdState(0, SPRULESTATE.SPRS_ACTIVE); } recContext.Recognition += new _ISpeechRecoContextEvents_RecognitionEventHandler(handleRecognition); //recContext.RecognitionForOtherContext += new _ISpeechRecoContextEvents_RecognitionForOtherContextEventHandler(handleRecognition); //System.Windows.Forms.MessageBox.Show("olari"); } } private void handleRecognition(int StreamNumber, object StreamPosition, SpeechLib.SpeechRecognitionType RecognitionType, SpeechLib.ISpeechRecoResult Result) { System.Windows.Forms.MessageBox.Show("entrei"); string temp = Result.PhraseInfo.GetText(0, -1, true); _recognizedText = ""; foreach (string word in recognizedWords) { if (temp.Contains(word)) { _recognizedText = word; } } } public void run() { if (File.Exists(System.Environment.GetEnvironmentVariable("PUBLIC") + "\\SoundLog\\Serialization\\Voices\\identifiedVoicesDLL.txt")) { deserializer = new XmlSerializer(_identifiedVoices.GetType()); FileStream fs = new FileStream(System.Environment.GetEnvironmentVariable("PUBLIC") + "\\SoundLog\\Serialization\\Voices\\identifiedVoicesDLL.txt", FileMode.Open); Object o = deserializer.Deserialize(fs); fs.Close(); _identifiedVoices = (double[])o; } if (File.Exists(System.Environment.GetEnvironmentVariable("PUBLIC") + "\\SoundLog\\Serialization\\Voices\\deletedVoicesDLL.txt")) { deserializer = new XmlSerializer(_deletedVoices.GetType()); FileStream fs = new FileStream(System.Environment.GetEnvironmentVariable("PUBLIC") + "\\SoundLog\\Serialization\\Voices\\deletedVoicesDLL.txt", FileMode.Open); Object o = deserializer.Deserialize(fs); fs.Close(); _deletedVoices = (ArrayList)o; } myTimer.Interval = 5000; myTimer.Tick += new EventHandler(clearData); myTimer.Start(); if (WaveNative.waveInGetNumDevs() > 0) { _waveFormat = new WaveFormat(_samples, 16, 2); _recorder = new WaveInRecorder(-1, _waveFormat, 8192 * 2, 3, new BufferDoneEventHandler(DataArrived)); _scaleHz = (double)_samples / _fftLength; _limit = (int)((double)_limitVoice / _scaleHz); SoundLogDLL.MelFrequencyCepstrumCoefficients.calculateFrequencies(_samples, _fftLength); } } startRecognition is a method for Speech Recognition that load a grammar and makes the recognition handler here: recContext.Recognition += new _ISpeechRecoContextEvents_RecognitionEventHandler(handleRecognition); Now I have a problem, when I call the method startRecognition before method run, both handlers (the recognition one and the handler for the Tick) work well. If a word is recognized, handlerRecognition method is called. But, when I call the method run before the method startRecognition, both methods seem to run well but then the recognition Handler is never executed! Even when I see that words are recognized (because they happear on the Windows Speech Recognition app). What can I do for the recognition handler be allways called?

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  • Using a general class for execution with try/catch/finally?

    - by antirysm
    I find myself having a lot of this in different methods in my code: try { runABunchOfMethods(); } catch (Exception ex) { logger.Log(ex); } What about creating this: public static class Executor { private static ILogger logger; public delegate void ExecuteThis(); static Executor() { // logger = ...GetLoggerFromIoC(); } public static void Execute(ExecuteThis executeThis) { try { executeThis(); } catch (Exception ex) { logger.Log(ex); } } } And just using it like this: private void RunSomething() { Method1(someClassVar); Method2(someOtherClassVar); } ... Executor.Execute(RunSomething); Are there any downsides to this approach? (You could add Executor-methods and delegates when you want a finally and use generics for the type of Exeception you want to catch...)

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  • How to pass event to method?

    - by tomaszs
    I would like to create a method that takes as a argument an event an adds eventHandler to it to handle it properly. Like this: I have 2 events: public event EventHandler Click; public event EventHandler Click2; Now i would like to pass particular event to my method like this (pseudocode): public AttachToHandleEvent(EventHandler MyEvent) { MyEvent += Item_Click; } private void Item_Click(object sender, EventArgs e) { MessageBox.Show("lalala"); } ToolStripMenuItem tool = new ToolStripMenuItem(); AttachToHandleEvent(tool.Click); Is it possible or do I not understand it good? Edit: I've noticed with help of you that this code worked fine, and returned to my project and noticed that when I pass event declared in my class it works, but when I pass event from other class id still does not work. Updated above example to reflect this issue. What I get is this error: The event 'System.Windows.Forms.ToolStripItem.Click' can only appear on the left hand side of += or -=

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  • C# Event Handlers automatically created by WinForms Designer

    - by RHaguiuda
    Just moved from VB.NET to C#. In VB to connect and Event Handler to a Sub we use the Handles clause. From what it seems, this do not exist in C#. After creating a simple application with a button I realize that Window Forms Designer automatically created an EventHandler to my button1_Click function (after I double clicked it), in Form1.Designer.cs with this code: this.button1.Click += new System.EventHandler(this.button1_Click); But, in VB, the WinForms Designer create the Handles clause in my class, in the function header. So, C# create the default EventHandler in designer file, while VB creates in main class with control resides. Is this correct? Am I missing something here?

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  • Javascript Prototype Best Practice Event Handlers

    - by nahum
    Hi this question is more a consulting of best practice, Sometimes when I'm building a complete ajax application I usually add elements dynamically for example. When you'r adding a list of items, I do something like: var template = new Template("<li id='list#{id}'>#{value}</li>"); var arrayTemplate = []; arrayOfItem.each(function(item, index){ arrayTemplate.push(template.evaluate( id : index, value : item)) }); after this two options add the list via "update" or "insert" ----- $("elementToUpdate").update("<ul>" + arrayTemplate.join("") + "</ul">); the question is how can I add the event handler without repeat the process of read the array, this is because if you try add a Event before the update or insert you will get an Error because the element isn't still on the DOM. so what I'm doing by now is after insert or update: arrayOfItem.each(function(item, index){ $("list" + index).observe("click", function(){ alert("I see the world"); }) }); so the question is exist a better way to doing this??????

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  • Handling Application Logic in Multiple AsyncTask onPostExecute()s

    - by stormin986
    I have three simultaneous instances of an AsyncTask for download three files. When two particular ones finish, at the end of onPostExecute() I check a flag set by each, and if both are true, I call startActivity() for the next Activity. I am currently seeing the activity called twice, or something that resembles this type of behavior. Since the screen does that 'swipe left' kind of transition to the next activity, it sometimes does it twice (and when I hit back, it goes back to the same activity). It's obvious two versions of the activity that SHOULD only get called once are being put on the Activity stack. The only way I can find that this is possible is if both AsyncTasks' onPostExecute() executed SO simultaneously that they were virtually running the same lines at the same time, since I set the 'itemXdownloaded' flag to true right before I check for both and call startActivity(). But this is happening enough that it's very hard for me to believe that both downloads are finishing precisely at the same time and having their onPostExecute()s so close together... Any thoughts on what could be going on here? General gist of code (details removed, ignore any syntactical errors I may have edited in): // In onPostExecute() switch (downloadID) { case DL1: dl1complete = true; break; case DL2: dl2complete = true; break; case DL3: dl3complete = true; break; } // If 1 and 2 are done, move on (DL3 still going in background) if ( downloadID != DL3 && dl1complete && dl2complete) { ParentClass.this.startActivity(new Intent(ParentClass.this, NextActivity.class)); }

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  • Reverse massive text file in Java

    - by DanJanson
    What would be the best approach to reverse a large text file that is uploaded asynchronously to a servlet that reverses this file in a scalable and efficient way? text file can be massive (gigabytes long) can assume mulitple server/clustered environment to do this in a distributed manner. open source libraries are encouraged to consider I was thinking of using Java NIO to treat file as an array on disk (so that I don't have to treat the file as a string buffer in memory). Also, I am thinking of using MapReduce to break up the file and process it in separate machines. Any input is appreciated. Thanks. Daniel

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  • Thoughts on try-catch blocks

    - by John Boker
    What are your thoughts on code that looks like this: public void doSomething() { try { // actual code goes here } catch (Exception ex) { throw; } } The problem I see is the actual error is not handled, just throwing the exception in a different place. I find it more difficult to debug because i don't get a line number where the actual problem is. So my question is why would this be good? ---- EDIT ---- From the answers it looks like most people are saying it's pointless to do this with no custom or specific exceptions being caught. That's what i wanted comments on, when no specific exception is being caught. I can see the point of actually doing something with a caught exception, just not the way this code is.

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