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  • Is this good C# style?

    - by burnt1ce
    Consider the following method signature: public static bool TryGetPolls(out List<Poll> polls, out string errorMessage) This method performs the following: accesses the database to generate a list of Poll objects. returns true if it was success and errorMessage will be an empty string returns false if it was not successful and errorMessage will contain an exception message. Is this good style? Update: Lets say i do use the following method signature: public static List<Poll> GetPolls() and in that method, it doesn't catch any exceptions (so i depend the caller to catch exceptions). How do i dispose and close all the objects that is in the scope of that method? As soon as an exception is thrown, the code that closes and disposes objects in the method is no longer reachable.

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  • C# Delegate Invoke Required Issue

    - by Goober
    Scenario I have a C# windows forms application that has a number of processes. These processes run on separate threads and all communicate back to the Main Form class with updates to a log window and a progress bar. I'm using the following code below, which up until now has worked fine, however, I have a few questions. Code delegate void SetTextCallback(string mxID, string text); public void UpdateLog(string mxID, string text) { if (txtOutput.InvokeRequired) { SetTextCallback d = new SetTextCallback(UpdateLog); this.BeginInvoke(d, new object[] { mxID, text }); } else { UpdateProgressBar(text); } } Question Will, calling the above code about 10 times a second, repeatedly, give me errors, exceptions or generally issues?.....Or more to the point, should it give me any of these problems? Occasionally I get OutofMemory Exceptions and the program always seems to crash around this bit of code......

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  • NoHostAvailableException With Cassandra & DataStax Java Driver If Large ResultSet

    - by hughj
    The setup: 2-node Cassandra 1.2.6 cluster replicas=2 very large CQL3 table with no secondary index Rowkey is a UUID.randomUUID().toString() read consistency set to ONE Using DataStax java driver 1.0 The request: Attempting to do a table scan by "SELECT some-col from schema.table LIMIT nnn;" The fail: Once I go beyond a certain nnn LIMIT, I start to get NoHostAvailableExceptions from the driver. It reads like this: com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: /10.181.13.239 ([/10.181.13.239] Unexpected exception triggered)) at com.datastax.driver.core.exceptions.NoHostAvailableException.copy(NoHostAvailableException.java:64) at com.datastax.driver.core.ResultSetFuture.extractCauseFromExecutionException(ResultSetFuture.java:214) at com.datastax.driver.core.ResultSetFuture.getUninterruptibly(ResultSetFuture.java:169) at com.jpmc.es.rtm.storage.impl.EventExtract.main(EventExtract.java:36) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120) Caused by: com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: /10.181.13.239 ([/10.181.13.239] Unexpected exception triggered)) at com.datastax.driver.core.RequestHandler.sendRequest(RequestHandler.java:98) at com.datastax.driver.core.RequestHandler$1.run(RequestHandler.java:165) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) Given: This is probably not the most enlightened thing to do to a large table with millions of rows, but this is how I learn what not to do, so I would really appreciate someone who could volunteer how this kind of error can be debugged. For example, when this happens, there are no indications that the nodes in the cluster ever had an issue with the request (there is nothing in the logs on either node that indicate any timeout or failure). Also, I enabled the trace on the driver, which gives you some nice autotrace (ala Oracle) info as long as the query succeeds. But in this case, the driver blows a NoHostAvailableException and no ExecutionInfo is available, so tracing has not provided any benefit in this case. I also find it interesting that this does not seem to be recorded as a timeout (my JMX consoles tell me no timeouts have occurred). So, I am left not understanding WHERE the failure is actually occurring. I am left with the idea that it is the driver that is having a problem, but I don't know how to debug it (and I would really like to). I have read several posts from folks that state that query'g for resultSets 10000 rows is probably not a good idea, and I am willing to accept this, but I would like to understand what is causing the exception and where the exception is happening. FWIW, I also tried bumping the timeout properties in the cassandra.yaml, but this made no difference whatsoever. I welcome any suggestions, anecdotes, insults, or monetary contributions for my registration in the house of moron-developers. Regards!!

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  • Common Pitfalls in Python

    - by Anurag Uniyal
    Today I was bitten again by "Mutable default arguments" after many years. I usually don't use mutable default arguments unless needed but I think with time I forgot about that, and today in the application I added tocElements=[] in a pdf generation function's argument list and now 'Table of Content' gets longer and longer after each invocation of "generate pdf" :) My question is what other things should I add to my list of things to MUST avoid? Mutable default arguments Import modules always same way e.g. from y import x and import x are different things, they are treated as different modules. Do not use range in place of lists because range() will become an iterator anyway, the following will fail: myIndexList = [0,1,3] isListSorted = myIndexList == range(3) # will fail in 3.0 isListSorted = myIndexList == list(range(3)) # will not same thing can be mistakenly done with xrange: `myIndexList == xrange(3)`. Catching multiple exceptions try: raise KeyError("hmm bug") except KeyError,TypeError: print TypeError It prints "hmm bug", though it is not a bug, it looks like we are catching exceptions of type KeyError,TypeError but instead we are catching KeyError only as variable TypeError, use this instead: try: raise KeyError("hmm bug") except (KeyError,TypeError): print TypeError

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  • Tomcat Exception-Type Ignoring Specific Exception for More General

    - by David Marks
    For one type of exception, IOException, I want to display one page. For all other exceptions I have a default error page. In my web.xml I have things setup like this: java.io.IOException /queryException.jsp java.lang.Exception /error.jsp The problem is the error.jsp is the only page that ever shows, even if an IOException is thrown. The order the tags appear in doesn't matter; if I remove the java.lang.Exception tag though, I can get queryException to show for IOExceptions. What is the solution here? How can I keep a general error page for all exceptions EXCEPT for those with specific pages?

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  • Does an IFilter Exist for Indexing Source Code Files?

    - by AMissico
    Anybody know of an IFilter that can index source code files beyond what the "Plain Text" filter can provide, with possibly a custom "Property Set" specific to programming? For example, I have 835MB in 41,000 files and 8,200 folders in my "Code Library" folder. I would like to perform searches such as "select distinct attributes on properties" or "select class exceptions" or "select classes with nested private classes". Preferrably, the IFilter can distinguish between various languages, so I can perform a query like "select class exceptions in VB.NET" or "select 'resume next' in VBScript". Other Examples "select all enum from folder('microsoft source code') in namespace 'system.io'"

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  • MySQLNonTransientConnectionException in jdbc program at run time

    - by Sunil Kumar Sahoo
    Hi I have created jdbc mysql connection. my program works fine for simple execution of query. But if i run the same program for more than 10 hour and execute query then i receives the following mysql exception. I have not used close() method anywhere. i created database connection and opened it forever and always execute query. there is no where that i explicitly mentioned timeout for connection. i am unable to identify the problem com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Connection.close() has already been called. Invalid operation in this state. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after statement closed. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) sample code for database connection: String driver = PropertyReader.getDriver(); String url = dbURLPath; Class.forName(driver); connectToServerDB = DriverManager.getConnection(url); connectToServerDB.setAutoCommit(false);

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  • NHybernate, the Parallel Framework, and SQL Server

    - by andy
    hey guys, we have a loop that: 1.Loops over several thousand xml files. Altogether we're parsing millions of "user" nodes. 2.In each iteration we parse a "user" xml, do custom deserialization 3.finally, in each iteration, we send our object to nhibernate for saving. We use: .SaveOrUpdateAndFlush(user); This is a lengthy process, and we thought it would be a perfect candidate for testing out the .NET 4.0 Parallel libraries. So we wrapped the loop in a: Parallel.ForEach(); After doing this, we start getting "random" Timeout Exceptions from SQL Server, and finally, after leaving it running all night, OutOfMemory unhandled exceptions. I haven't done deep debugging on this yet, but what do you guys think. Is this simply a limitation of SQL Server, or could it be our NHibernate setup, or what? cheers andy

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  • Java: custom-exception-error

    - by HH
    $ javac TestExceptions.java TestExceptions.java:11: cannot find symbol symbol : class test location: class TestExceptions throw new TestExceptions.test("If you see me, exceptions work!"); ^ 1 error Code import java.util.*; import java.io.*; public class TestExceptions { static void test(String message) throws java.lang.Error{ System.out.println(message); } public static void main(String[] args){ try { // Why does it not access TestExceptions.test-method in the class? throw new TestExceptions.test("If you see me, exceptions work!"); }catch(java.lang.Error a){ System.out.println("Working Status: " + a.getMessage() ); } } }

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  • NHibernate, the Parallel Framework, and SQL Server

    - by andy
    hey guys, we have a loop that: 1.Loops over several thousand xml files. Altogether we're parsing millions of "user" nodes. 2.In each iteration we parse a "user" xml, do custom deserialization 3.finally, in each iteration, we send our object to nhibernate for saving. We use: .SaveOrUpdateAndFlush(user); This is a lengthy process, and we thought it would be a perfect candidate for testing out the .NET 4.0 Parallel libraries. So we wrapped the loop in a: Parallel.ForEach(); After doing this, we start getting "random" Timeout Exceptions from SQL Server, and finally, after leaving it running all night, OutOfMemory unhandled exceptions. I haven't done deep debugging on this yet, but what do you guys think. Is this simply a limitation of SQL Server, or could it be our NHibernate setup, or what? cheers andy

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  • skip-limit ignored for skippable exception thrown from writer

    - by ck
    i am working on a project with spring batch 2.0.2 and have skippable exception set up in the config. for exceptions thrown from the processor everything works fine. it skips and once the limit is execeed the job fails (or stops). for exceptions thrown from the writer (same chunk) it keeps skipping. the skip-limit doesnt seem to matter. maybe i missunderstood and skipping and writer don't go together or maybe i am missing a configuration. does anyone know how to skip issues - with a limit - within the writer properly?

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  • Need to determine if ELMAH is logging an unhandled exception or one raised by ErrorSignal.Raise()

    - by Ronnie Overby
    I am using the Elmah Logged event in my Global.asax file to transfer users to a feedback form when an unhandled exception occurs. Sometimes I log other handled exceptions. For example: ErrorSignal.FromCurrentContext().Raise(new System.ApplicationException("Program code not found: " + Student.MostRecentApplication.ProgramCode)); // more code that should execute after logging this exception The problem I am having is that the Logged event gets fired for both unhandled and these handled, raised exceptions. Is there a way to determine, in the Logged event handler, whether the exception was raised via ErrorSignal class or was simply unhandled? Are there other Elmah events that I can take advantage of?

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  • Strategies for Error Handling in .NET Web Services

    - by Jarrod
    I have a fairly substantial library of web services built in .NET that I use as a data model for our company web sites. In most .NET applications I use the Global ASAX file for profiling, logging, and creating bug reports for all exceptions thrown by the application. Global ASAX isn't available for web services so I'm curious as to what other strategies people have come up with to work around this limitation. Currently I just do something along these lines: <WebMethod()> _ Public Function MyServiceMethod(ByVal code As Integer) As String Try Return processCode(code) Catch ex As Exception CustomExHandler(ex) 'call a custom function every time to log exceptions Return errorObject End Try End Function Anybody have a better way of doing things besides calling a function inside the Catch?

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  • Grails deploy on Tomcat6

    - by Jack
    Hello, while trying to deploy a Grails application into tomcat6 I ran into some problems: I used the grails war command to build up a war, then copied it to var/lib/tomcat6/webapps and tried to restart the container. I had to change default Tomcat policy to skip security exceptions, since I couldn't access environment variable (like grails.env), then tried again but it gives me an exception related to instantiating something, but it's not clear where should I try to fix the error, according to tomcat6 logs the problem is: SEVERE: Exception sending context initialized event to listener instance of class org.codehaus.groovy.grails.web.context.GrailsC$ org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'pluginManager' defined in ServletContext$ at java.lang.Thread.run(Thread.java:619) Caused by: org.codehaus.groovy.grails.exceptions.NewInstanceCreationException: Could not create a new instance of class [Hiberna$ ... 1 more Caused by: java.lang.NoClassDefFoundError: org.hibernate.cfg.Environment It seems like it's unable to load org.hibernate.cfg.Environment class. I checked the applicationContext.xml and it refers to grails.xml to search for plugins, in this last file I actually have HibernateGrailsPlugin. Where should I look to find if the plugin is present?

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  • ELMAH: Only sending specific exception type via mail

    - by Sir Code-A-Lot
    Hi, I have ELMAH set up for a webapp, logging exceptions to a SQL server. I wish to have ELMAH send me an email too, but only when a specific exception is thrown (ie. MySpecialException). ELMAH must still log all exceptions to SQL server. I know you can do it programmatically in global.asax, but I'd prefer to use web.config. So, how do I restrict ELMAH error mails to filter out everything but a specific exception type, using web.config?

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  • A simple way (in java) to remove headers from xml files

    - by Andersson Melo
    I need remove non-xml tags from file generated by another program. The file is some like this: Executing Command - Blah.exe ... -----Command Output----- HTTP/1.1 200 OK Connection: close Content-Type: text/xml <?xml version="1.0"?> <testResults> <right>7</right> <wrong>4</wrong> <ignores>0</ignores> <exceptions>0</exceptions> </finalCounts> </testResults> Exit-Code: 15 How to remove the non-xml text easily in java?

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  • Delete temp file during finally vs delete output file during catch

    - by Russell
    This is in Java 6. I've seen more than once that people create temp files, do something, then rename it to the output file. Everything is wrapped in a try-finally block, where the temp file is deleted in finally in case something goes wrong in between. try { //do something with tempFile //do something with tempFile //do something with tempFile tempFile.renameTo(outputFile); } finally { if (tempFile.exists()) tempFile.delete() } I was wondering what are the benefits of doing that instead of doing something to the output file directly and delete it in case of exceptions. try { //do something with outputFile //do something with outputFile //do something with outputFile } catch (Exception e) { if (outputFile.exists()) outputFile.delete(); } My guess is that deleting temp files in finally benefits me when the try block can throw many kinds of exceptions. Is my guess right? What else?

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  • Condition checking vs. Exception handling

    - by Aidas Bendoraitis
    When is exception handling more preferable than condition checking? There are many situations where I can choose using one or the other. For example, this is a summing function which uses a custom exception: # module mylibrary class WrongSummand(Exception): pass def sum_(a, b): """ returns the sum of two summands of the same type """ if type(a) != type(b): raise WrongSummand("given arguments are not of the same type") return a + b # module application using mylibrary from mylibrary import sum_, WrongSummand try: print sum_("A", 5) except WrongSummand: print "wrong arguments" And this is the same function, which avoids using exceptions # module mylibrary def sum_(a, b): """ returns the sum of two summands if they are both of the same type """ if type(a) == type(b): return a + b # module application using mylibrary from mylibrary import sum_ c = sum_("A", 5) if c is not None: print c else: print "wrong arguments" I think that using conditions is always more readable and manageable. Or am I wrong? What are the proper cases for defining APIs which raise exceptions and why?

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  • Is there anything wrong with my Factory class?

    - by Alex
    class PieceFactory { @SuppressWarnings("rawtypes") public Piece createPiece(String pieceType) throws Throwable{ Class pieceClass = Class.forName(pieceType); Piece piece = (Piece) pieceClass.newInstance(); return piece; } } I'm not all used to handling exceptions yet therefore I'm just throwing them, but everywhere I use a method that uses this factory it tells me I have to throw exceptions like throwable. For example, in one of my classes I have a method that instantiates a lot of objects using the method that uses the factory. I can use the method in that class by just throwing the exception, however it won't work if I try to pass a reference to that class to another class and then use the method from there. Then it forces me to try catch the exception. I probably don't need a factory but it seemed interesting and I'd like to try to use patterns. The reason I created the factory was that I have 6 subclasses of Piece and I wan't to use a method to instantiate them by passing the type of subclass I want as an argument to the method.

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  • SqlBulkCopy unusual TimeOut Error

    - by ChrisHDog
    I have a SqlBulkCopy operation that is taking data from an MS-Access 2007 database (via OleDbConnection) and using SqlBulkCopy to transfer that data to a SQL Server database. This has previously been working and continues to work for one MS-Access database, but not the other. I get the error message: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. It is hard to believe it is a timeout ast the oledbCommand.CommandTimeout = 0 the sqlBulkCopy.BulkCopyTimeout = 0 and on either side (MS-Access and SQL Server the timeouts have now been set to 0). Are there other issues/exceptions that the above error message could be hiding? Is there a way to determine what the base cause of a sqlBulkCopy.WriteToServer exception is (there doesn't appear to be any inner exceptions etc...)

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  • How to check function parameters in Go

    - by deamon
    Guava Preconditions allows to check method parameters in Java easily. public void doUsefulThings(Something s, int x, int position) { checkNotNull(s); checkArgument(x >= 0, "Argument was %s but expected nonnegative", x); checkElementIndex(position, someList.size()); // ... } These check methods raise exceptions if the conditions are not met. Go has no exceptions but indicates errors with return values. So I wonder how an idiomatic Go version of the above code would look like.

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