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  • When to use try/catch

    - by coffeeaddict
    I'm always finding myself wanting to put a try/catch around the lets say Business Layer methods. But I feel though that I don't need a try/catch if I'm simply rethrowing it up to the Presentation Layer. Is that right? I should not be rethrowing an exception from code that's wrapped in a try/catch in a BL method and should be letting the caller which would be from the Presentation Layer code be using a try/catch to handle it there? The BL method will throw an error without the try/catch anyway..the compiler will. So it wouldn't make sense to use a try/catch in a BL method that's to be consumed by a layer higher up correct?

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  • Exceptions from WCF

    - by adrianm
    What exceptions can be thrown from a WCF client? I usually catch CommunicationFaultedException, CommunicationException, TimoutException and some other but from time to time new ones occur, e.g. most recently QuotaExceededException There is no common base to catch (except Exception) so does anyone have a complete list?

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  • Delphi: Application error logging in the field

    - by mawg
    Using Delphi 7, I wonder if there is a free component which will collect diagnostic information as my application runs at a remote site and will help me to debug error reports. Maybe it records each menu item selected, control clicked, text input, etc? Maybe it just dumps the stack on a crash. Maybe it does something else ... I don't mind adding code (e.g at the start and end of each procedure), as that might generate more useful info than a fully automatic system. I am not sure if the solution ought to "phone home" or if it is enough to produce a text file which can be emailed to me. Any suggestions?

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  • Perl TCP Server handling multiple Client connections

    - by Matt
    I'll preface this by saying I have minimal experience with both Perl and Socket programming, so I appreciate any help I can get. I have a TCP Server which needs to handle multiple Client connections simultaneously and be able to receive data from any one of the Clients at any time and also be able to send data back to the Clients based on information it's received. For example, Client1 and Client2 connect to my Server. Client2 sends "Ready", the server interprets that and sends "Go" to Client1. The following is what I have written so far: my $sock = new IO::Socket::INET { LocalHost => $host, // defined earlier in code LocalPort => $port, // defined earlier in code Proto => 'tcp', Listen => SOMAXCONN, Reuse => 1, }; die "Could not create socket $!\n" unless $sock; while ( my ($new_sock,$c_addr) = $sock->accept() ) { my ($client_port, $c_ip) = sockaddr_in($c_addr); my $client_ipnum = inet_ntoa($c_ip); my $client_host = ""; my @threads; print "got a connection from $client_host", "[$client_ipnum]\n"; my $command; my $data; while ($data = <$new_sock>) { push @threads, async \&Execute, $data; } } sub Execute { my ($command) = @_; // if($command) = "test" { // send "go" to socket1 print "Executing command: $command\n"; system($command); } I know both of my while loops will be blocking and I need a way to implement my accept command as a thread, but I'm not sure the proper way of writing it.

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  • Session handling in python / django

    - by Gaurav
    I am creating an application that lets users login using Google, Facebook and the website's native login. The site is being built in Python / Django. What would be the best way to handle login, session management and user authentication? I do not want to use the in-built Django user management. I am using Django very sparingly(URLs, templates)

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  • Browser not handling exception from AJAX panel, ASP.NET c#

    - by Grant
    Hi, i am having trouble catching errors in an AJAX panel. Even when i throw an exception in the c# code behind the front end completely ignores it. Here is the code i have setup, can anyone see why? I ideally want to show a js alert window on error. Code Behind: protected void btnX_Click(object sender, EventArgs e) { throw new ApplicationException("test"); } protected void ScriptManager_AsyncPostBackError(object sender, AsyncPostBackErrorEventArgs e) { ScriptManager.AsyncPostBackErrorMessage = e.Exception.Message; } Markup: <script type="text/javascript" language="javascript"> Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler); function EndRequestHandler(sender, e) { window.alert(e.get_error().name); } </script> <asp:ScriptManager ID="ScriptManager" runat="server" AllowCustomErrorsRedirect="true" OnAsyncPostBackError="ScriptManager_AsyncPostBackError" />

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  • Are there SqlExceptions which throw but commit their data anyway?

    - by Jonn
    I've recently encountered the error: System.Data.SqlClient.SqlException: The transaction log for database 'mydatabase' is full. To find out why space in the log cannot be reused, see the log_reuse_wait_desc column in sys.databases on one of my windows services. It's supposed to retry after catching an Sql Exception, what I didn't expect was that it seemed like the data was still going through (I'm using an SqlBulkCopy btw) regardless of it throwing an exception. I've never encountered this scenario before. I'd like to know if there are other scenarios where such a thing like this might happen, and if this thing is entirely possible at all in the first place? PS. If anyone knows the error code to the above exception, that would help a great deal as well.

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  • Problem with handling click event of bitmap

    - by shaina
    i am using navigationClick method to handle click event of Bitmap images & Buttons it works fine when i dont use VerticalFieldManger . But when i adjust positions of field using this field manager then it doesnt capture click event of all controls just on capture Index(0) click which i think is verticalFieldmanager not other (Bitmaps & Buttons fields) Plzzzzzz help how to resolve it code is protected boolean navigationClick(int status, int time) { Field field = this.getFieldWithFocus(); if(field.getIndex()==0) { Dialog.alert("Index 0 (bitmaP) clicked"); } if(field.getIndex()==1) { Dialog.alert("Index 1(Button 1) clicked"); } if(field.getIndex()==2) { Dialog.alert("Index 2 (Button2) Clicked"); } if(field.getIndex()==3) { Dialog.alert("Index 3(bitmap2) Clicked"); } }

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  • When designing an event, is it a good idea to prevent listeners from being added twice?

    - by Matt
    I am creating an event-based API where a user can subscribe to an event by adding listener objects (as is common in Java or C#). When the event is raised, all subscribed listeners are invoked with the event information. I initially decided to prevent adding an event listener more than once. If a listener is added that already exists in the listener collection, it is not added again. However, after thinking about it some more, it doesn't seem that most event-based structures actually prevent this. Was my initial instinct wrong? I'm not sure which way to go here. I guess I thought that preventing addition of an existing listener would help to avoid a common programming error. Then again, it could also hide a bug that would lead to code being run multiple times when it shouldn't.

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  • Do you catch expected exceptions in the controller or business service of your asp.net mvc application

    - by Pascal
    I am developing an asp.net mvc application where user1 could delete data records which were just loaded before by user2. User2 either changes this non-existent data record (Update) or is doing an insert with this data in another table that a foreign-key constraint is violated. Where do you catch such expected exceptions? In the Controller of your asp.net mvc application or in the business service? Just a sidenote: I only catch the SqlException here if its a ForeignKey constraint exception to tell the user that another user has deleted a certain parent record and therefore he can not create the testplan. But this code is not fully implemented yet! Controller:   public JsonResult CreateTestplan(Testplan testplan)   {    bool success = false;    string error = string.Empty;    try   {    success = testplanService.CreateTestplan(testplan);    }   catch (SqlException ex)    {    error = ex.Message;    }    return Json(new { success = success, error = error }, JsonRequestBehavior.AllowGet);   } OR Business service: public Result CreateTestplan(Testplan testplan) { Result result = new Result(); try { using (var con = new SqlConnection(_connectionString)) using (var trans = new TransactionScope()) { con.Open(); _testplanDataProvider.AddTestplan(testplan); _testplanDataProvider.CreateTeststepsForTestplan(testplan.Id, testplan.TemplateId); trans.Complete(); result.Success = true; } } catch (SqlException e) { result.Error = e.Message; } return result; } then in the Controller: public JsonResult CreateTestplan(Testplan testplan)   {    Result result = testplanService.CreateTestplan(testplan);       return Json(new { success = result.success, error = result.error }, JsonRequestBehavior.AllowGet);   }

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  • When and why does an EventHandler require objects to be final?

    - by Michiel Borkent
    I have the following code from a GWT Project that is part of the onModuleLoad() method (similar to Java's main method, if you don't know GWT): final TextBox t1 = new TextBox(); final Label lt1 = new Label(); t1.addKeyUpHandler(new KeyUpHandler() { @Override public void onKeyUp(KeyUpEvent event) { // TODO Auto-generated method stub if (!(t1.getText().matches("\\w{2}-\\w{2}-\\w{2}"))) lt1.setText("Invalid."); else lt1.setText("OK."); } }); Why do the two local variables have to be final here?

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  • In Asp.net (c#) i'm not able to catch any exception properly????

    - by Anand
    In Asp.net (c#),i'm not able to catch exception(FileNotFoundException) properly... i don't know the reason..Actually File s not there..But catch statement fails to catch the exception.. here is the code.. try { System.Drawing.Image imgg1 = System.Drawing.Image.FromFile(Server.MapPath("").ToString() + "\\images\\img1.jpg"); } catch (FileNotFoundException) { Response.Write("<script>alert('Please Select and upload Student's Photo');</script>"); }

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  • Returning JSON or XML for Exceptions in Jersey

    - by Dominic
    My goal is to have an error bean returned on a 404 with a descriptive message when a object is not found, and return the same MIME type that was requested. I have a look up resource, which will return the specified object in XML or JSON based on the URI (I have setup the com.sun.jersey.config.property.resourceConfigClass servlet parameter so I dont need the Accept header. My JAXBContextResolver has the ErrorBean.class in its list of types, and the correct JAXBContext is returned for this class because I can see in the logs). eg: http://foobar.com/rest/locations/1.json @GET @Path("{id}") @Produces({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML}) public Location getCustomer(@PathParam("id") int cId) { //look up location from datastore .... if (location == null) { throw new NotFoundException("Location" + cId + " is not found"); } } And my NotFoundException looks like this: public class NotFoundException extends WebApplicationException { public NotFoundException(String message) { super(Response.status(Response.Status.NOT_FOUND). entity(new ErrorBean( message, Response.Status.NOT_FOUND.getStatusCode() ) .build()); } } The ErrorBean is as follows: @XmlRootElement(name = "error") public class ErrorBean { private String errorMsg; private int errorCode; //no-arg constructor, property constructor, getter and setters ... } However, I'm always getting a 204 No Content response when I try this. I have hacked around, and if I return a string and specify the mime type this works fine: public NotFoundException(String message) { super(Response.status(Response.Status.NOT_FOUND). entity(message).type("text/plain").build()); } I have also tried returning an ErrorBean as a resource. This works fine: {"errorCode":404,"errorMsg":"Location 1 is not found!"}

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  • Help me find article on Multi-threading and Event Handling in Java

    - by JDR
    I once read an article on how to properly write event handlers for multi-threading in Java, but I can't for the life of me find it anymore. It described the pitfalls and potentials for deadlocks that can occur when firing events (not Swing events mind you, but general events like model update notifications). To clarify, the situation would be as such: // let's say this is code from an MVC model somewhere public void setSomeProperty(String myProperty){ if(!this.myProperty.equals(myProperty)){ this.myProperty = myProperty; fireMyPropertyChangedEvent(...); } } The article described how passing control to arbitrary external listener code was a potential cause for deadlock. I now find myself in a situation where I need to fire such events in a multithreaded environment and I would very much like to read the article again to see what it has to say before I continue. Does anyone know the article I'm referring to? I believe it came as a (fairly short) PDF. It started off with an initial naive implementation and incrementally pointed out flaws and improved upon it. It ended with a sort of final proper-way-to-fire-multithreaded-events. I've searched endlessly in my browse history and on google, but all I could find were endless amounts topics on Swing event dispatch threads. Thank you.

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  • Questions Regarding Handling of Received SMS

    - by Edwin
    Hi, i have managed to successfully write a little test app that can receive and send SMS, but got a couple of questions. (That's 'cos part of the code i copied from elsewhere and i would like to understand better). In my AndroidManifest as well as the sub-class of BroadcastReceiver, there is reference to the string literal "android.provider.Telephony.SMS_RECEIVED". However, i couldn't find any reference in the API that mentions this. Could someone point me to some reference that lists/explains these? As part of getting the message from the Intent, i did this: Object[] pdus = (Object[]) intent.getExtras().get("pdus"); Again this question is related to the use of hardcoded string literal. Where is the string "pdus" listed and described? Thanks in advance!

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  • Java File Handling, what did I do wrong?

    - by Urda
    Wrote up a basic file handler for a Java Homework assignment, and when I got the assignment back I had some notes about failing to catch a few instances: Buffer from file could have been null. File was not found File stream wasn't closed Here is the block of code that is used for opening a file: /** * Create a Filestream, Buffer, and a String to store the Buffer. */ FileInputStream fin = null; BufferedReader buffRead = null; String loadedString = null; /** Try to open the file from user input */ try { fin = new FileInputStream(programPath + fileToParse); buffRead = new BufferedReader(new InputStreamReader(fin)); loadedString = buffRead.readLine(); fin.close(); } /** Catch the error if we can't open the file */ catch(IOException e) { System.err.println("CRITICAL: Unable to open text file!"); System.err.println("Exiting!"); System.exit(-1); } The one comment I had from him was that fin.close(); needed to be in a finally block, which I did not have at all. But I thought that the way I have created the try/catch it would have prevented an issue with the file not opening. Let me be clear on a few things: This is not for a current assignment (not trying to get someone to do my own work), I have already created my project and have been graded on it. I did not fully understand my Professor's reasoning myself. Finally, I do not have a lot of Java experience, so I was a little confused why my catch wasn't good enough.

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  • How to pass non-fatal warnings from a library

    - by wRAR
    A library function parses a file and returns an object. If a parser encounters unknown data, missing values etc., it shouldn't throw an exception and stop parsing (because this is not fatal), but there should be a way to pass information about these things to a caller (so that warnings can be displayed in the UI, for example). How can these warning be returned? I'm thinking of passing a callback function/object into the library, are there any other possible solutions?

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  • Ruby Methods: return an usage string when insufficient arguments are given

    - by Shyam
    Hi, After creating a serious bunch of classes, with initialize methods, loading them in IRb requires to look back at the code. However, I think it should be easy enough to return a usage message, instead of: ArgumentError: wrong number of arguments (0 for 9) So I prefer to return a string with the human readable arguments, by example using "puts" or just a return of a string. Now I have seen the rescue keyword inside begin-end code, but I wonder how I could catch the ArgumentError when the initialize method is called. Thank you for your answers, feedback and comments!

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  • [c++] accessing the hidden 'this' pointer

    - by Kyle
    I have a GUI architecture wherein elements fire events like so: guiManager->fireEvent(BUTTON_CLICKED, this); Every single event fired passes 'this' as the caller of the event. There is never a time I dont want to pass 'this', and further, no pointer except for 'this' should ever be passed. This brings me to a problem: How can I assert that fireEvent is never given a pointer other than 'this', and how can I simplify (and homogenize) calls to fireEvent to just: guiManager->fireEvent(BUTTON_CLICKED); At this point, I'm reminded of a fairly common compiler error when you write something like this: class A { public: void foo() {} }; class B { void oops() { const A* a = new A; a->foo(); } }; int main() { return 0; } Compiling this will give you ../src/sandbox.cpp: In member function ‘void B::oops()’: ../src/sandbox.cpp:7: error: passing ‘const A’ as ‘this’ argument of ‘void A::foo()’ discards qualifiers because member functions pass 'this' as a hidden parameter. "Aha!" I say. This (no pun intended) is exactly what I want. If I could somehow access the hidden 'this' pointer, it would solve both issues I mentioned earlier. The problem is, as far as I know you can't (can you?) and if you could, there would be outcries of "but it would break encapsulation!" Except I'm already passing 'this' every time, so what more could it break. So, is there a way to access the hidden 'this', and if not are there any idioms or alternative approaches that are more elegant than passing 'this' every time?

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  • Handling large datasets with PHP/Drupal

    - by jo
    Hi all, I have a report page that deals with ~700k records from a database table. I can display this on a webpage using paging to break up the results. However, my export to PDF/CSV functions rely on processing the entire data set at once and I'm hitting my 256MB memory limit at around 250k rows. I don't feel comfortable increasing the memory limit and I haven't got the ability to use MySQL's save into outfile to just serve a pre-generated CSV. However, I can't really see a way of serving up large data sets with Drupal using something like: $form = array(); $table_headers = array(); $table_rows = array(); $data = db_query("a query to get the whole dataset"); while ($row = db_fetch_object($data)) { $table_rows[] = $row->some attribute; } $form['report'] = array('#value' => theme('table', $table_headers, $table_rows); return $form; Is there a way of getting around what is essentially appending to a giant array of arrays? At the moment I don't see how I can offer any meaningful report pages with Drupal due to this. Thanks

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  • 'Advanced' Console Application

    - by keynesiancross
    Hi all, I'm not sure if this question has been answered elsewhere and I can't seem to find anything through google that isn't a "Hello World" example... I'm coding in C# .NET 4.0. I'm trying to develop a console application that will open, display text, and then wait for the user to input commands, where the commands will run particular business logic. For example: If the user opens the application and types "help", I want to display a number of statements etc etc. I'm not sure how to code the 'event handler' for user input though. Hopefully this makes sense. Any help would be much appreciated! Cheers.

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  • Correct Exceptions in C++

    - by Dr.Ackula
    I am just learning how to handle errors in my C++ code. I wrote this example that looks for a text file called some file, and if its not found will throw an exception. #include <iostream> #include <fstream> using namespace std; int main() { int array[90]; try { ifstream file; file.open("somefile.txt"); if(!file.good()) throw 56; } catch(int e) { cout<<"Error number "<<e<<endl; } return 0; } Now I have two questions. First I would like to know if I am using Exceptions correctly. Second, (assuming the first is true) what is the benefit to using them vs an If else statement?

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