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  • Showing custom model validation exceptions in the Django admin site.

    - by Guy Bowden
    I have a booking model that needs to check if the item being booked out is available. I would like to have the logic behind figuring out if the item is available centralised so that no matter where I save the instance this code validates that it can be saved. At the moment I have this code in a custom save function of my model class: def save(self): if self.is_available(): # my custom check availability function super(MyObj, self).save() else: # this is the bit I'm stuck with.. raise forms.ValidationError('Item already booked for those dates') This works fine - the error is raised if the item is unavailable, and my item is not saved. I can capture the exception from my front end form code, but what about the Django admin site? How can I get my exception to be displayed like any other validation error in the admin site?

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  • How to prevent swallowing exceptions caused by unset expectations for a mocked object?

    - by Schultz9999
    I am looking for a way to modify catch block depending on if it's executed during the unit test run or not. The purpose is basically to detect/setup mock expectations which are swallowed because catch doesn't rethrow. I am using MSTest. One obvious thing is using preprocessor but I don't think it works. Especially if to use DEBUG define. There should be an easy way to detect that, shouldn't it? I must have been looking for something wrong because I couldn't find much info on that. try {...} catch(Exception) { Log(...); #if DEBUG throw; #endif }

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  • Serious problem with WCF, GridViews, Callbacks and ExecuteReaders exceptions.

    - by barjed
    Hi, I have this problem that is driving me insane. I have a project to deliver before Thursday. Basically an app consiting of three components that communicate with each other in WCF. I have one console app and one Windows Forms app. The console app is a server that's connected to the database. You can add records to it via the Windows Forms client that connectes with the server through the WCF. The code for the client: namespace BankAdministratorClient { [CallbackBehavior(ConcurrencyMode = ConcurrencyMode.Single, UseSynchronizationContext = false)] public partial class Form1 : Form, BankServverReference.BankServerCallback { private BankServverReference.BankServerClient server = null; private SynchronizationContext interfaceContext = null; public Form1() { InitializeComponent(); interfaceContext = SynchronizationContext.Current; server = new BankServverReference.BankServerClient(new InstanceContext(this), "TcpBinding"); server.Open(); server.Subscribe(); refreshGridView(""); } public void refreshClients(string s) { SendOrPostCallback callback = delegate(object state) { refreshGridView(s); }; interfaceContext.Post(callback, s); } public void refreshGridView(string s) { try { userGrid.DataSource = server.refreshDatabaseConnection().Tables[0]; } catch (Exception ex) { MessageBox.Show(ex.ToString()); } } private void buttonAdd_Click(object sender, EventArgs e) { server.addNewAccount(Int32.Parse(inputPIN.Text), Int32.Parse(inputBalance.Text)); } private void Form1_FormClosing(object sender, FormClosingEventArgs e) { try { server.Unsubscribe(); server.Close(); }catch{} } } } The code for the server: namespace SSRfinal_tcp { class Program { static void Main(string[] args) { Console.WriteLine(MessageHandler.dataStamp("The server is starting up")); using (ServiceHost server = new ServiceHost(typeof(BankServer))) { server.Open(); Console.WriteLine(MessageHandler.dataStamp("The server is running")); Console.ReadKey(); } } } [ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Single, InstanceContextMode = InstanceContextMode.PerCall, IncludeExceptionDetailInFaults = true)] public class BankServer : IBankServerService { private static DatabaseLINQConnectionDataContext database = new DatabaseLINQConnectionDataContext(); private static List<IBankServerServiceCallback> subscribers = new List<IBankServerServiceCallback>(); public void Subscribe() { try { IBankServerServiceCallback callback = OperationContext.Current.GetCallbackChannel<IBankServerServiceCallback>(); if (!subscribers.Contains(callback)) subscribers.Add(callback); Console.WriteLine(MessageHandler.dataStamp("A new Bank Administrator has connected")); } catch { Console.WriteLine(MessageHandler.dataStamp("A Bank Administrator has failed to connect")); } } public void Unsubscribe() { try { IBankServerServiceCallback callback = OperationContext.Current.GetCallbackChannel<IBankServerServiceCallback>(); if (subscribers.Contains(callback)) subscribers.Remove(callback); Console.WriteLine(MessageHandler.dataStamp("A Bank Administrator has been signed out from the connection list")); } catch { Console.WriteLine(MessageHandler.dataStamp("A Bank Administrator has failed to sign out from the connection list")); } } public DataSet refreshDatabaseConnection() { var q = from a in database.GetTable<Account>() select a; DataTable dt = q.toTable(rec => new object[] { q }); DataSet data = new DataSet(); data.Tables.Add(dt); Console.WriteLine(MessageHandler.dataStamp("A Bank Administrator has requested a database data listing refresh")); return data; } public void addNewAccount(int pin, int balance) { Account acc = new Account() { PIN = pin, Balance = balance, IsApproved = false }; database.Accounts.InsertOnSubmit(acc); database.SubmitChanges(); database.addNewAccount(pin, balance, false); subscribers.ForEach(delegate(IBankServerServiceCallback callback) { callback.refreshClients("New operation is pending approval."); }); } } } This is really simple and it works for a single window. However, when you open multiple instances of the client window and try to add a new record, the windows that is performing the insert operation crashes with the ExecuteReader error and the " requires an open and available connection. the connection's current state is connecting" bla bla stuff. I have no idea what's going on. Please advise.

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  • How to handle error in this case? By Exceptions or boolean or something else

    - by TP
    I am trying to create a Response class in Java which has a method void setResponse(String response); Different response subclasses will have different requirements for the response. The string that is passed to the function is received from the user. What is the correct way of handling a wrong response? Should the function throw an exception like IllegalResponseException Should the function be declared like boolean setResponse(String response, String errorMsg) and return false if the response is wrong and set the error message to the appropriate value

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  • Preventing the "[YourProgramName] has stopped working" dialog on unhandled exceptions.

    - by Serapth
    I have a WinForm application, with some dependencies on an external library that can on occasion cause an exception outside of the running threads context. As it stands now, this is completely OK behavior ( well, except of course the exception ) and we wired up AppDomain.CurrentDomain.UnhandledException to simply restart the program. The only problem is, the [Your Program] has stopped working like the one below, appears: Is there a way to prevent this dialog from appearing at all, be it in the AppDomain unhandled exception handler or in a config setting, as no end users are going to be reading it and it just holds up resources until it is clicked.

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  • Zend Framework: How to handle exceptions in Ajax requests?

    - by understack
    Normally when an exception is thrown, Error controller takes command and displays error page with regular common header and footer. This behavior is not wanted in Ajax request. Because in case of error, whole html page is sent over. And in cases where I'm directly loading the content of http response in a div, this is even more unwanted. Instead in case of Ajax request, I just want to receive 'the actual error' thrown by exception. How can I do this? I think, one dirty way could be: set a var in ajax request and process accordingly. Not a good solution.

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  • What is wrong in this bit of MyID3 code? (error code is just Exceptions)

    - by user3697621
    Okay, so, this was supposed to get the paths of all mp3 files in a folder, read their metadata and put in an arraylist. public static List<String> OrgMetadata(List<String> rawgenrelist){ File folder = new File("C:\\SOM\\"); File[] listOfFiles = folder.listFiles(); //File path = listOfFiles; for (int i = 0; i < listOfFiles.length; i++) { String pt = listOfFiles[i].getAbsolutePath(); File src = new File(pt); MusicMetadataSet src_set = new MyID3().read(src); if (src_set != null && listOfFiles[i].isFile()) { IMusicMetadata metadata = src_set.getSimplified(); rawgenrelist.add(metadata.getGenreName()); } } List<String> genrelist; genrelist = new ArrayList(new HashSet(rawgenrelist)); return genrelist; }

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  • Qt : crash due to delete (trying to handle exceptions...)

    - by Seub
    I am writing a program with Qt, and I would like it to show a dialog box with a Exit | Restart choice whenever an error is thrown somewhere in the code. What I did causes a crash and I really can't figure out why it happens, I was hoping you could help me understanding what's going on. Here's my main.cpp: #include "my_application.hpp" int main(int argc, char *argv[]) { std::cout << std::endl; My_Application app(argc, argv); return app.exec(); } And here's my_application:hpp: #ifndef MY_APPLICATION_HPP #define MY_APPLICATION_HPP #include <QApplication> class Window; class My_Application : public QApplication { public: My_Application(int& argc, char ** argv); virtual ~My_Application(); virtual bool notify(QObject * receiver, QEvent * event); private: Window *window_; void exit(); void restart(); }; #endif // MY_APPLICATION_HPP Finally, here's my_application.cpp: #include "my_application.hpp" #include "window.hpp" #include <QMessageBox> My_Application::My_Application(int& argc, char ** argv) : QApplication(argc, argv) { window_ = new Window; window_->setAttribute(Qt::WA_DeleteOnClose, false); window_->show(); } My_Application::~My_Application() { delete window_; } bool My_Application::notify(QObject * receiver, QEvent * event) { try { return QApplication::notify(receiver, event); } catch(QString error_message) { window_->setEnabled(false); QMessageBox message_box; message_box.setWindowTitle("Error"); message_box.setIcon(QMessageBox::Critical); message_box.setText("The program caught an unexpected error:"); message_box.setInformativeText("What do you want to do? <br>"); QPushButton *restart_button = message_box.addButton(tr("Restart"), QMessageBox::RejectRole); QPushButton *exit_button = message_box.addButton(tr("Exit"), QMessageBox::RejectRole); message_box.setDefaultButton(restart_button); message_box.exec(); if ((QPushButton *) message_box.clickedButton() == exit_button) { exit(); } else if ((QPushButton *) message_box.clickedButton() == restart_button) { restart(); } } return false; } void My_Application::exit() { window_->close(); //delete window_; return; } void My_Application::restart() { window_->close(); //delete window_; window_ = new Window; window_->show(); return; } Note that the line window_->setAttribute(Qt::WA_DeleteOnClose, false); means that window_ (my main window) won't be deleted when it is closed. The code I've written above works, but as far as I understand, there's a memory leak: I should uncomment the line //delete window_; in My_Application::exit() and My_Application::restart(). But when I do that, the program crashes when I click restart (or exit but who cares). (I'm not sure this is useful, in fact it might be misleading, but here's what my debugger tells me: a segmentation fault occurs in QWidgetPrivate::PaintOnScreen() const which is called by a function called by a function... called by My_Application::notify()) When I do some std::couts, I notice that the program runs through the entire restart() function and in fact through the entire notify() function before it crashes. I have no idea why it crashes. Thanks in advance for your insights! Update: I've noticed that My_Application::notify() is called very often. For example, it is called a bunch of times while the error dialog box is open, also during the execution of the restart function. The crash actually occurs in the subfunction QApplication::notify(receiver, event). This is not too surprising in light of the previous remark (the receiver has probably been deleted) But even if I forbid the function My_Application::notify() to do anything while restart() is executed, it still crashes (after having called My_Application::notify() a bunch of times, like 15 times, isn't that weird)? How should I proceed? Maybe I should say (to make the question slightly more relevant) that my class My_Application also has a "restore" function, which I've not copied here to try to keep things short. If I just had that restart feature I wouldn't bother too much, but I do want to have that restore feature. I should also say that if I keep the code with the "delete window_" commented, the problem is not only a memory leak, it still crashes sometimes apparently. There must surely be a way to fix this! But I'm clueless, I'd really appreciate some help! Thanks in advance.

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  • Why Is Faulty Behaviour In The .NET Framework Not Fixed?

    - by Alois Kraus
    Here is the scenario: You have a Windows Form Application that calls a method via Invoke or BeginInvoke which throws exceptions. Now you want to find out where the error did occur and how the method has been called. Here is the output we do get when we call Begin/EndInvoke or simply Invoke The actual code that was executed was like this:         private void cInvoke_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.Invoke);         }            [MethodImpl(MethodImplOptions.NoInlining)]         void InvokingFunction(CallMode mode)         {             switch (mode)             {                 case CallMode.Invoke:                     this.Invoke(new MethodInvoker(GenerateError));   The faulting method is called GenerateError which does throw a NotImplementedException exception and wraps it in a NotSupportedException.           [MethodImpl(MethodImplOptions.NoInlining)]         void GenerateError()         {             F1();         }           private void F1()         {             try             {                 F2();             }             catch (Exception ex)             {                 throw new NotSupportedException("Outer Exception", ex);             }         }           private void F2()         {            throw new NotImplementedException("Inner Exception");         } It is clear that the method F2 and F1 did actually throw these exceptions but we do not see them in the call stack. If we directly call the InvokingFunction and catch and print the exception we can find out very easily how we did get into this situation. We see methods F1,F2,GenerateError and InvokingFunction directly in the stack trace and we see that actually two exceptions did occur. Here is for comparison what we get from Invoke/EndInvoke System.NotImplementedException: Inner Exception     StackTrace:    at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)     at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)     at WindowsFormsApplication1.AppForm.InvokingFunction(CallMode mode)     at WindowsFormsApplication1.AppForm.cInvoke_Click(Object sender, EventArgs e)     at System.Windows.Forms.Control.OnClick(EventArgs e)     at System.Windows.Forms.Button.OnClick(EventArgs e) The exception message is kept but the stack starts running from our Invoke call and not from the faulting method F2. We have therefore no clue where this exception did occur! The stack starts running at the method MarshaledInvoke because the exception is rethrown with the throw catchedException which resets the stack trace. That is bad but things are even worse because if previously lets say 5 exceptions did occur .NET will return only the first (innermost) exception. That does mean that we do not only loose the original call stack but all other exceptions and all data contained therein as well. It is a pity that MS does know about this and simply closes this issue as not important. Programmers will play a lot more around with threads than before thanks to TPL, PLINQ that do come with .NET 4. Multithreading is hyped quit a lot in the press and everybody wants to use threads. But if the .NET Framework makes it nearly impossible to track down the easiest UI multithreading issue I have a problem with that. The problem has been reported but obviously not been solved. .NET 4 Beta 2 did not have changed that dreaded GetBaseException call in MarshaledInvoke to return only the innermost exception of the complete exception stack. It is really time to fix this. WPF on the other hand does the right thing and wraps the exceptions inside a TargetInvocationException which makes much more sense. But Not everybody uses WPF for its daily work and Windows forms applications will still be used for a long time. Below is the code to repro the issues shown and how the exceptions can be rendered in a meaningful way. The default Exception.ToString implementation generates a hard to interpret stack if several nested exceptions did occur. 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; using System.Threading; using System.Globalization; using System.Runtime.CompilerServices;   namespace WindowsFormsApplication1 {     public partial class AppForm : Form     {         enum CallMode         {             Direct = 0,             BeginInvoke = 1,             Invoke = 2         };           public AppForm()         {             InitializeComponent();             Thread.CurrentThread.CurrentUICulture = CultureInfo.InvariantCulture;             Application.ThreadException += new System.Threading.ThreadExceptionEventHandler(Application_ThreadException);         }           void Application_ThreadException(object sender, System.Threading.ThreadExceptionEventArgs e)         {             cOutput.Text = PrintException(e.Exception, 0, null).ToString();         }           private void cDirectUnhandled_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.Direct);         }           private void cDirectCall_Click(object sender, EventArgs e)         {             try             {                 InvokingFunction(CallMode.Direct);             }             catch (Exception ex)             {                 cOutput.Text = PrintException(ex, 0, null).ToString();             }         }           private void cInvoke_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.Invoke);         }           private void cBeginInvokeCall_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.BeginInvoke);         }           [MethodImpl(MethodImplOptions.NoInlining)]         void InvokingFunction(CallMode mode)         {             switch (mode)             {                 case CallMode.Direct:                     GenerateError();                     break;                 case CallMode.Invoke:                     this.Invoke(new MethodInvoker(GenerateError));                     break;                 case CallMode.BeginInvoke:                     IAsyncResult res = this.BeginInvoke(new MethodInvoker(GenerateError));                     this.EndInvoke(res);                     break;             }         }           [MethodImpl(MethodImplOptions.NoInlining)]         void GenerateError()         {             F1();         }           private void F1()         {             try             {                 F2();             }             catch (Exception ex)             {                 throw new NotSupportedException("Outer Exception", ex);             }         }           private void F2()         {            throw new NotImplementedException("Inner Exception");         }           StringBuilder PrintException(Exception ex, int identLevel, StringBuilder sb)         {             StringBuilder builtStr = sb;             if( builtStr == null )                 builtStr = new StringBuilder();               if( ex == null )                 return builtStr;                 WriteLine(builtStr, String.Format("{0}: {1}", ex.GetType().FullName, ex.Message), identLevel);             WriteLine(builtStr, String.Format("StackTrace: {0}", ShortenStack(ex.StackTrace)), identLevel + 1);             builtStr.AppendLine();               return PrintException(ex.InnerException, ++identLevel, builtStr);         }               void WriteLine(StringBuilder sb, string msg, int identLevel)         {             foreach (string trimmedLine in SplitToLines(msg)                                            .Select( (line) => line.Trim()) )             {                 for (int i = 0; i < identLevel; i++)                     sb.Append('\t');                 sb.Append(trimmedLine);                 sb.AppendLine();             }         }           string ShortenStack(string stack)         {             int nonAppFrames = 0;             // Skip stack frames not part of our app but include two foreign frames and skip the rest             // If our stack frame is encountered reset counter to 0             return SplitToLines(stack)                               .Where((line) =>                               {                                   nonAppFrames = line.Contains("WindowsFormsApplication1") ? 0 : nonAppFrames + 1;                                   return nonAppFrames < 3;                               })                              .Select((line) => line)                              .Aggregate("", (current, line) => current + line + Environment.NewLine);         }           static char[] NewLines = Environment.NewLine.ToCharArray();         string[] SplitToLines(string str)         {             return str.Split(NewLines, StringSplitOptions.RemoveEmptyEntries);         }     } }

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  • Monitoring ASP.NET Application

    - by imran_ku07
        Introduction:          There are times when you may need to monitor your ASP.NET application's CPU and memory consumption, so that you can fine-tune your ASP.NET application(whether Web Form, MVC or WebMatrix). Also, sometimes you may need to see all the exceptions(and their details) of your application raising, whether they are handled or not. If you are creating an ASP.NET application in .NET Framework 4.0, then you can easily monitor your application's CPU or memory consumption and see how many exceptions your application raising. In this article I will show you how you can do this.       Description:           With .NET Framework 4.0, you can turn on the monitoring of CPU and memory consumption by setting AppDomain.MonitoringEnabled property to true. Also, in .NET Framework 4.0, you can register a callback method to AppDomain.FirstChanceException event to monitor the exceptions being thrown within your application's AppDomain. Turning on the monitoring and registering a callback method will add some additional overhead to your application, which will hurt your application performance. So it is better to turn on these features only if you have following properties in web.config file,   <add key="AppDomainMonitoringEnabled" value="true"/> <add key="FirstChanceExceptionMonitoringEnabled" value="true"/>             In case if you wonder what does FirstChanceException mean. It simply means the first notification of an exception raised by your application. Even CLR invokes this notification before the catch block that handles the exception. Now just update global.asax.cs file as,   string _item = "__RequestExceptionKey"; protected void Application_Start() { SetupMonitoring(); } private void SetupMonitoring() { bool appDomainMonitoringEnabled, firstChanceExceptionMonitoringEnabled; bool.TryParse(ConfigurationManager.AppSettings["AppDomainMonitoringEnabled"], out appDomainMonitoringEnabled); bool.TryParse(ConfigurationManager.AppSettings["FirstChanceExceptionMonitoringEnabled"], out firstChanceExceptionMonitoringEnabled); if (appDomainMonitoringEnabled) { AppDomain.MonitoringIsEnabled = true; } if (firstChanceExceptionMonitoringEnabled) { AppDomain.CurrentDomain.FirstChanceException += (object source, FirstChanceExceptionEventArgs e) => { if (HttpContext.Current == null)// If no context available, ignore it return; if (HttpContext.Current.Items[_item] == null) HttpContext.Current.Items[_item] = new RequestException { Exceptions = new List<Exception>() }; (HttpContext.Current.Items[_item] as RequestException).Exceptions.Add(e.Exception); }; } } protected void Application_EndRequest() { if (Context.Items[_item] != null) { //Only add the request if atleast one exception is raised var reqExc = Context.Items[_item] as RequestException; reqExc.Url = Request.Url.AbsoluteUri; Application.Lock(); if (Application["AllExc"] == null) Application["AllExc"] = new List<RequestException>(); (Application["AllExc"] as List<RequestException>).Add(reqExc); Application.UnLock(); } }               Now browse to Monitoring.cshtml file, you will see the following screen,                            The above screen shows you the total bytes allocated, total bytes in use and CPU usage of your application. The above screen also shows you all the exceptions raised by your application which is very helpful for you. I have uploaded a sample project on github at here. You can find Monitoring.cshtml file on this sample project. You can use this approach in ASP.NET MVC, ASP.NET WebForm and WebMatrix application.       Summary:          This is very important for administrators/developers to manage and administer their web application after deploying to production server. This article will help administrators/developers to see the memory and CPU usage of their web application. This will also help administrators/developers to see all the exceptions your application is throwing whether they are swallowed or not. Hopefully you will enjoy this article too.   SyntaxHighlighter.all()

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  • Monitoring .NET ASP.NET Applications

    - by James Hollingworth
    I have a number of applications running on top of ASP.NET I want to monitor. The main things I care about are: Exceptions: We currently some custom code which will email us when an exception occurs. If the application is failing hard it will crash our outlook... I know (and use) elmah which partly solves the problem however it is still just a big table of exceptions with a pretty(ish) UI. I want something that makes sense of all of these exceptions (e.g. groups exceptions, alerts when new ones occur, tells me what the common ones are that I should fix, etc) Logging: We currently log to files which are then accessible via a shared folder which dev's grep & tail. Does anyone know of better ways of presenting this information. In an ideal world I want to associate it with exceptions. Performance: Request times, memory usage, cpu, etc. whatever stats I can get I'm guessing this is probably going to be solved by a number of tools, has anyone got any suggestions?

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  • Throwing an AggregateException in my own code

    - by Pat
    How should I go about collecting exceptions and putting them into an AggregateException to re-throw? For my specific code, I have a loop and will have zero or more exceptions thrown from a part of the code. I was hoping to just add the new exceptions to the AggregateException as they arise, but the documentation sort of indicates that it should be constructed with all the Exceptions at once (there is no method to add an Exception to the object). And what about creating a new AE every time and just including the previous AE in the list of exceptions? Seems a hokey way to do it. Any better ideas?

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  • Java exception translations

    - by user3079275
    Apologies if this has been discussed on other threads but I find it helps clarify my thinking when I am forced to write down my questions. I am trying to properly understand the concept of checked vs unchecked exceptions and exception translation in Java but I am getting confused. So far I understood that checked exceptions are exceptions that need to be always caught in a try/catch block otherwise I get a compile time error. This is to force programmers to think about abnormal situations that might happen at run time (like disk full etc). Is this right? What I did not get was why we have unchecked exceptions, when are they useful? Is it only during development time to debug code that might access an illegal array index etc? This confusion is because I see that Error exceptions are also unchecked as is RunTimeException but its not clear to me why they are both lumped together into an unchecked category?

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  • Extending the ADF Controller exception handler

    - by frank.nimphius
    The Oracle ADF controller provides a declarative option for developers to define a view activity, method activity or router activity to handle exceptions in bounded or unbounded task flows. Exception handling however is for exceptions only and not handling all types of Throwable. Furthermore, exceptions that occur during the JSF RENDER RESPONSE phase are not looked at either as it is considered too late in the cycle. For developers to try themselves to handle unhandled exceptions in ADF Controller, it is possible to extend the default exception handling, while still leveraging the declarative configuration. To add your own exception handler: · Create a Java class that extends ExceptionHandler · Create a textfile with the name “oracle.adf.view.rich.context.Exceptionhandler” (without the quotes) and store it in .adf\META-INF\services (you need to create the “services” folder) · In the file, add the absolute name of your custom exception handler class (package name and class name without the “.class” extension) For any exception you don't handle in your custom exception handler, just re-throw it for the default handler to give it a try … import oracle.adf.view.rich.context.ExceptionHandler; public class MyCustomExceptionHandler extends ExceptionHandler { public MyCustomExceptionHandler() {      super(); } public void handleException(FacesContext facesContext,                              Throwable throwable, PhaseId phaseId)                              throws Throwable {    String error_message;    error_message = throwable.getMessage();    //check error message and handle it if you can    if( … ){          //handle exception        …    }    else{       //delegate to the default ADFc exception handler        throw throwable;}    } } Note however, that it is recommended to first try and handle exceptions with the ADF Controller default exception handling mechanism. In the past, I've seen attempts on OTN to handle regular application use cases with custom exception handlers for where there was no need to override the exception handler. So don't go for this solution to quickly and always think of alternative solutions. Sometimes a try-catch-final block does it better than sophisticated web exception handling.

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  • Resetting Update Manager

    - by Emre
    How can I fix Update Manager in 12.04, which hangs when I try to install any update, while sudo apt-get upgrade works fine? I suspect it has something to do with my python installation. This is the error message: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/defer/__init__.py", line 475, in _inline_callbacks result = gen.send(result) File "/usr/lib/python2.7/dist-packages/aptdaemon/client.py", line 1622, in _run_transaction_helper daemon = get_aptdaemon(self.bus) File "/usr/lib/python2.7/dist-packages/aptdaemon/client.py", line 1696, in get_aptdaemon False), File "/usr/lib/python2.7/dist-packages/dbus/bus.py", line 241, in get_object follow_name_owner_changes=follow_name_owner_changes) File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 248, in __init__ self._named_service = conn.activate_name_owner(bus_name) File "/usr/lib/python2.7/dist-packages/dbus/bus.py", line 180, in activate_name_owner self.start_service_by_name(bus_name) File "/usr/lib/python2.7/dist-packages/dbus/bus.py", line 278, in start_service_by_name 'su', (bus_name, flags))) File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 651, in call_blocking message, timeout) dbus.exceptions.DBusException: org.freedesktop.DBus.Error.Spawn.ChildExited: Launch helper exited with unknown return code 1 Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/defer/__init__.py", line 475, in _inline_callbacks result = gen.send(result) File "/usr/lib/python2.7/dist-packages/aptdaemon/client.py", line 1622, in _run_transaction_helper daemon = get_aptdaemon(self.bus) File "/usr/lib/python2.7/dist-packages/aptdaemon/client.py", line 1696, in get_aptdaemon False), File "/usr/lib/python2.7/dist-packages/dbus/bus.py", line 241, in get_object follow_name_owner_changes=follow_name_owner_changes) File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 248, in __init__ self._named_service = conn.activate_name_owner(bus_name) File "/usr/lib/python2.7/dist-packages/dbus/bus.py", line 180, in activate_name_owner self.start_service_by_name(bus_name) File "/usr/lib/python2.7/dist-packages/dbus/bus.py", line 278, in start_service_by_name 'su', (bus_name, flags))) File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 651, in call_blocking message, timeout) dbus.exceptions.DBusException: org.freedesktop.DBus.Error.Spawn.ChildExited: Launch helper exited with unknown return code 1 dbus.exceptions.DBusException: org.freedesktop.DBus.Error.Spawn.ChildExited: Launch helper exited with unknown return code 1 Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/defer/__init__.py", line 473, in _inline_callbacks result = gen.throw(result.type, result.value, result.traceback) File "/usr/lib/python2.7/dist-packages/UpdateManager/backend/InstallBackendAptdaemon.py", line 52, in commit downgrade, defer=True) dbus.exceptions.DBusException: org.freedesktop.DBus.Error.Spawn.ChildExited: Launch helper exited with unknown return code 1

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  • Handling Errors In PHP When Using MVC

    - by James Jeffery
    I've been using Codeigniter a lot recently, but one thing that gets on my nerves is handling errors and displaying them to the user. I've never been good at handling errors without it getting messy. My main concern is when returning errors to the user. Is it good practice to use exceptions and throw/catch exceptions rather than returning 0 or 1 from functions and then using if/else to handle the errors. Thus, making it easier to inform the user about the issue. I tend to go away from exceptions. My Java tutor at university some years ago told me "exceptions shouldn't be used in production code it's more for debugging". I get the feeling he was lying. But, an example, I have code that adds a user to a database. During the process more than 1 thing could go wrong, such as a database issue, a duplicate entry, a server issue, etc. When an issue happens during registration the user needs to know about it. What's the best way to handle errors in PHP, keeping in mind that I'm using an MVC framework.

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  • PerlRegEx vs RegularExpressionsCore Delphi Units

    - by Jan Goyvaerts
    The RegularExpressionsCore unit that is part of Delphi XE is based on the latest class-based PerlRegEx unit that I developed. Embarcadero only made a few changes to the unit. These changes are insignificant enough that code written for earlier versions of Delphi using the class-based PerlRegEx unit will work just the same with Delphi XE. The unit was renamed from PerlRegEx to RegularExpressionsCore. When migrating your code to Delphi XE, you can choose whether you want to use the new RegularExpressionsCore unit or continue using the PerlRegEx unit in your application. All you need to change is which unit you add to the uses clause in your own units. Indentation and line breaks in the code were changed to match the style used in the Delphi RTL and VCL code. This does not change the code, but makes it harder to diff the two units. Literal strings in the unit were separated into their own unit called RegularExpressionsConsts. These strings are only used for error messages that indicate bugs in your code. If your code uses TPerlRegEx correctly then the user should not see any of these strings. My code uses assertions to check for out of bounds parameters, while Embarcadero uses exceptions. Again, if you use TPerlRegEx correctly, you should never get any assertions or exceptions. The Compile method raises an exception if the regular expression is invalid in both my original TPerlRegEx component and Embarcadero’s version. If your code allows the user to provide the regular expression, you should explicitly call Compile and catch any exceptions it raises so you can tell the user there is a problem with the regular expression. Even with user-provided regular expressions, you shouldn’t get any other assertions or exceptions if your code is correct. Note that Embarcadero owns all the rights to their RegularExpressionsCore unit. Like all the other RTL and VCL units, this unit cannot be distributed by myself or anyone other than Embarcadero. I do retain the rights to my original PerlRegEx unit which I will continue to make available for those using older versions of Delphi.

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  • Exception Handling And Other Contentious Political Topics

    - by Justin Jones
    So about three years ago, around the time of my last blog post, I promised a friend I would write this post. Keeping promises is a good thing, and this is my first step towards easing back into regular blogging. I fully expect him to return from Pennsylvania to buy me a beer over this. However, it’s been an… ahem… eventful three years or so, and blogging, unfortunately, got pushed to the back burner on my priority list, along with a few other career minded activities. Now that the personal drama of the past three years is more or less resolved, it’s time to put a few things back on the front burner. What I consider to be proper exception handling practices is relatively well known these days. There are plenty of blog posts out there already on this topic which more or less echo my opinions on this topic. I’ll try to include a few links at the bottom of the post. Several years ago I had an argument with a co-worker who posited that exceptions should be caught at every level and logged. This might seem like sanity on the surface, but the resulting error log looked something like this: Error: System.SomeException Followed by small stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace.   These were all the same exception. The problem with this approach is that the error log, if you run any kind of analytics on in, becomes skewed depending on how far up the stack trace your exception was thrown. To mitigate this problem, we came up with the concept of the “PreLoggedException”. Basically, we would log the exception at the very top level and subsequently throw the exception back up the stack encapsulated in this pre-logged type, which our logging system knew to ignore. Now the error log looked like this: Error: System.SomeException Followed by small stack trace. Much cleaner, right? Well, there’s still a problem. When your exception happens in production and you go about trying to figure out what happened, you’ve lost more or less all context for where and how this exception was thrown, because all you really know is what method it was thrown in, but really nothing about who was calling the method or why. What gives you this clue is the entire stack trace, which we’re losing here. I believe that was further mitigated by having the logging system pull a system stack trace and add it to the log entry, but what you’re actually getting is the stack for how you got to the logging code. You’re still losing context about the actual error. Not to mention you’re executing a whole slew of catch blocks which are sloooooooowwwww……… In other words, we started with a bad idea and kept band-aiding it until it didn’t suck quite so bad. When I argued for not catching exceptions at every level but rather catching them following a certain set of rules, my co-worker warned me “do yourself a favor, never express that view in any future interviews.” I suppose this is my ultimate dismissal of that advice, but I’m not too worried. My approach for exception handling follows three basic rules: Only catch an exception if 1. You can do something about it. 2. You can add useful information to it. 3. You’re at an application boundary. Here’s what that means: 1. Only catch an exception if you can do something about it. We’ll start with a trivial example of a login system that uses a file. Please, never actually do this in production code, it’s just concocted example. So if our code goes to open a file and the file isn’t there, we get a FileNotFound exception. If the calling code doesn’t know what to do with this, it should bubble up. However, if we know how to create the file from scratch we can create the file and continue on our merry way. When you run into situations like this though, What should really run through your head is “How can I avoid handling an exception at all?” In this case, it’s a trivial matter to simply check for the existence of the file before trying to open it. If we detect that the file isn’t there, we can accomplish the same thing without having to handle in in a catch block. 2. Only catch an exception if you can do something about it. Continuing with the poorly thought out file based login system we contrived in part 1, if the code calls a Login(…) method and the FileNotFound exception is thrown higher up the stack, the code that calls Login must account for a FileNotFound exception. This is kind of counterintuitive because the calling code should not need to know the internals of the Login method, and the data file is an implementation detail. What makes more sense, assuming that we didn’t implement any of the good advice from step 1, is for Login to catch the FileNotFound exception and wrap it in a new exception. For argument’s sake we’ll say LoginSystemFailureException. (Sorry, couldn’t think of anything better at the moment.) This gives us two stack traces, preserving the original stack trace in the inner exception, and also is much more informative to the calling code. 3. Only catch an exception if you’re at an application boundary. At some point we have to catch all the exceptions, even the ones we don’t know what to do with. WinForms, ASP.Net, and most other UI technologies have some kind of built in mechanism for catching unhandled exceptions without fatally terminating the application. It’s still a good idea to somehow gracefully exit the application in this case if possible though, because you can no longer be sure what state your application is in, but nothing annoys a user more than an application just exploding. These unhandled exceptions need to be logged, and this is a good place to catch them. Ideally you never want this option to be exercised, but code as though it will be. When you log these exceptions, give them a “Fatal” status (e.g. Log4Net) and make sure these bugs get handled in your next release. That’s it in a nutshell. If you do it right each exception will only get logged once and with the largest stack trace possible which will make those 2am emergency severity 1 debugging sessions much shorter and less frustrating. Here’s a few people who also have interesting things to say on this topic:  http://blogs.msdn.com/b/ericlippert/archive/2008/09/10/vexing-exceptions.aspx http://www.codeproject.com/Articles/9538/Exception-Handling-Best-Practices-in-NET I know there’s more but I can’t find them at the moment.

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  • Anatomy of a serialization killer

    - by Brian Donahue
    As I had mentioned last month, I have been working on a project to create an easy-to-use managed debugger. It's still an internal tool that we use at Red Gate as part of product support to analyze application errors on customer's computers, and as such, should be easy to use and not require installation. Since the project has got rather large and important, I had decided to use SmartAssembly to protect all of my hard work. This was trivial for the most part, but the loading and saving of results was broken by SA after using the obfuscation, rendering the loading and saving of XML results basically useless, although the merging and error reporting was an absolute godsend and definitely worth the price of admission. (Well, I get my Red Gate licenses for free, but you know what I mean!)My initial reaction was to simply exclude the serializable results class and all of its' members from obfuscation, and that was just dandy, but a few weeks on I decided to look into exactly why serialization had broken and change the code to work with SA so I could write any new code to be compatible with SmartAssembly and save me some additional testing and changes to the SA project.In simple terms, SA does all that it can to prevent serialization problems, for instance, it will not obfuscate public members of a DLL and it will exclude any types with the Serializable attribute from obfuscation. This prevents public members and properties from being made private and having the name changed. If the serialization is done inside the executable, however, public members have the access changed to private and are renamed. That was my first problem, because my types were in the executable assembly and implemented ISerializable, but did not have the Serializable attribute set on them!public class RedFlagResults : ISerializable        {        }The second problem caused by the pruning feature. Although RedFlagResults had public members, they were not truly properties, and used the GetObjectData() method of ISerializable to serialize the members. For that reason, SA could not exclude these members from pruning and further broke the serialization. public class RedFlagResults : ISerializable        {                public List<RedFlag.Exception> Exceptions;                 #region ISerializable Members                 public void GetObjectData(SerializationInfo info, StreamingContext context)                {                                info.AddValue("Exceptions", Exceptions);                }                 #endregionSo to fix this, it was necessary to make Exceptions a proper property by implementing get and set on it. Also, I added the Serializable attribute so that I don't have to exclude the class from obfuscation in the SA project any more. The DoNotPrune attribute means I do not need to exclude the class from pruning.[Serializable, SmartAssembly.Attributes.DoNotPrune]        public class RedFlagResults        {                public List<RedFlag.Exception> Exceptions {get;set;}        }Similarly, the Exception class gets the Serializable and DoNotPrune attributes applied so all of its' properties are excluded from obfuscation.Now my project has some protection from prying eyes by scrambling up the code so it's harder to reverse-engineer, without breaking anything. SmartAssembly has also provided the benefit of merging so that the end-user doesn't need to extract all of the DLL files needed by RedFlag into a directory, and can be run directly from the .zip archive. When an error occurs (hey, I'm only human!), an exception report can be sent to me so I can see what went wrong without having to, er, debug the debugger.

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  • When to use a user defined Exception and some good examples/best Practices?

    - by Atomiton
    I would assume that most User-defined Exceptions are for Business Logic level exceptions, but what are some good reasons to use a User-Defined Exception and what are some good examples? Is a user-defined exception's only advantage that you can define a consistent Error Message? What logic can be written inside exceptions to make them truly more useful? After all, can't you just do this: throw new Exception("Some Error Message");

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  • Visual Studio: What happened to the "Break when an exception is unhandled" option?

    - by Adrian Grigore
    Hi, As far as I remember, Visual Studio (both 2008 and 2010) used to have an option to break either on thrown exceptions or on unhandled exceptions. Now when I bring up the Exceptions dialog (Ctr+Alt+E), it just offers to break when an exception is thrown: http://screencast.com/t/NDk3NDYxZD I've tried resizing to the columns in that dialog, but that did not help. Is this a bug, or am I missing something?

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  • How to make a try-catch block that iterates through all objects of a list and keeps on calling a met

    - by aperson
    Basically iterating through a list and, - Invoke method on first object - Catch first exception (if any); if there are no more exceptions to catch, return normally. Otherwise, keep on invoking method until all exceptions are caught. - Move on to next object. I can iterate through each object, invoke the method, and catch one exception but I do not know how to continuously invoke the method on it and keep on catching exceptions :S Thanks :)

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