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• JRuby app throws exception in Spring

  - by mat3001

  I am trying to run a JRuby app in Spring. I use Eclipse to run it. But it doesn't compile. Does anybody know what's going on here? Exception in thread "Launcher:/oflaDemo" [INFO] [Launcher:/oflaDemo] org.springframework.beans.factory.support.DefaultListableBeanFactory - Destroying singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@4a009ab0: defining beans [placeholderConfig,web.context,web.scope,web.handler,demoService.service]; parent: org.springframework.beans.factory.support.DefaultListableBeanFactory@f5d8d75 [INFO] [Launcher:/installer] org.red5.server.service.Installer - Installer service created org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'web.scope' defined in ServletContext resource [/WEB-INF/red5-web.xml]: Initialization of bean failed; nested exception is org.springframework.beans.TypeMismatchException: Failed to convert property value of type [org.springframework.scripting.jruby.JRubyScriptFactory] to required type [org.red5.server.api.IScopeHandler] for property 'handler'; nested exception is java.lang.IllegalArgumentException: Cannot convert value of type [org.springframework.scripting.jruby.JRubyScriptFactory] to required type [org.red5.server.api.IScopeHandler] for property 'handler': no matching editors or conversion strategy found at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:480) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409) at java.security.AccessController.doPrivileged(Native Method) I don't have a lot of experience with Spring, so I would really appreciate hits. If you're familiar with red5 - yes it's the oflademo app supplied by red5.

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• (JBoss) Problem with .war project on production, while test works

  - by ikky

  Hello. I have a java project (using Spring mvc) which i have built and deployed on my local computer. It runs on a JBoss application server, and works fine on the local machine. The next step i do, is to copy the deployed project.war from the local machine to the server which has the same development environment as the local machine. I stop the JBoss server, delete the cache, and run the JBoss server again. When i now try to run one of the pages(xx.xxx.xxx:8080/webservice/test.htm), i get this exception: exception org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:583) root cause java.lang.NullPointerException com.project.db.DBCustomer.isCredentialsCorrect(DBCustomer.java:44) com.project.CreateHController.handleRequest(CreateHController.java:60) org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:48) org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:875) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:807) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:571) org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:501) javax.servlet.http.HttpServlet.service(HttpServlet.java:697) javax.servlet.http.HttpServlet.service(HttpServlet.java:810) org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:75) It seems like none of my classes are reachable. Does anyone have any idea of what is wrong? btw: as i said, the project works fine on the local machine.

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• Rescuing a failed WCF call

  - by illdev

  Hello, I am happily using Castle's WcfFacility. From Monorail I know the handy concept of Rescues - consumer friendly results that often, but not necessarily, contain Data about what went wrong. I am creating a Silverlight application right now, doing quite a few WCF service calls. All these request return an implementation of public class ServiceResponse { private string _messageToUser = string.Empty; private ActionResult _result = ActionResult.Success; public ActionResult Result // Success, Failure, Timeout { get { return _result; } set { _result = value; } } public string MessageToUser { get { return _messageToUser; } set { _messageToUser = value; } } } public abstract class ServiceResponse<TResponseData> : ServiceResponse { public TResponseData Data { get; set; } } If the service has trouble responding the right way, I would want the thrown Exception to be intercepted and converted to the expected implementation. base on the thrown exception, I would want to pass on a nice message. here is how one of the service methods looks like: [Transaction(TransactionMode.Requires)] public virtual SaveResponse InsertOrUpdate(WarehouseDto dto) { var w = dto.Id > 0 ? _dao.GetById(dto.Id) : new Warehouse(); w.Name = dto.Name; _dao.SaveOrUpdate(w); return new SaveResponse { Data = new InsertData { Id = w.Id } }; } I need the thrown Exception for the Transaction to be rolled back, so i cannot actually catch it and return something else. Any ideas, where I could hook in?

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• SQL Server error handling: exceptions and the database-client contract

  - by gbn

  We’re a team of SQL Servers database developers. Our clients are a mixed bag of C#/ASP.NET, C# and Java web services, Java/Unix services and some Excel. Our client developers only use stored procedures that we provide and we expect that (where sensible, of course) they treat them like web service methods. Some our client developers don’t like SQL exceptions. They understand them in their languages but they don’t appreciate that the SQL is limited in how we can communicate issues. I don’t just mean SQL errors, such as trying to insert “bob” into a int column. I also mean exceptions such as telling them that a reference value is wrong, or that data has already changed, or they can’t do this because his aggregate is not zero. They’d don’t really have any concrete alternatives: they’ve mentioned that we should output parameters, but we assume an exception means “processing stopped/rolled back. How do folks here handle the database-client contract? Either generally or where there is separation between the DB and client code monkeys. Edits: we use SQL Server 2005 TRY/CATCH exclusively we log all errors after the rollback to an exception table already we're concerned that some of our clients won't check output paramaters and assume everything is OK. We need errors flagged up for support to look at. everything is an exception... the clients are expected to do some message parsing to separate information vs errors. To separate our exceptions from DB engine and calling errors, they should use the error number (ours are all 50,000 of course)

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• Is boost shared_ptr <XXX> thread safe?

  - by sxingfeng

  I have a question about boost :: shared_ptr. There are lots of thread. class CResource { xxxxxx } class CResourceBase { public: void SetResource(shared_ptr<CResource> res) { m_Res = res; } shared_ptr<CResource> GetResource() { return m_Res; } private: shared_ptr<CResource> m_Res; } CResourceBase base; //---------------------------------------------- Thread A: while (true) { ...... shared_ptr<CResource> nowResource = base.GetResource(); nowResource.doSomeThing(); ... } Thread B: shared_ptr<CResource> nowResource; base.SetResource(nowResource); ... //----------------------------------------------------------- If thread A do not care the nowResource is the newest . Will this part of code have problem? I mean when ThreadB do not SetResource completely, Thread A get a wrong smart point by GetResource? Another question : what does thread-safe mean? If I do not care about whether the resource is newest, will the shared_ptr nowResource crash the program when the nowResource is released or will the problem destroy the shared_point?

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• java : how to handle the design when template methods throw exception when overrided method not throw

  - by jiafu

  when coding. try to solve the puzzle: how to design the class/methods when InputStreamDigestComputor throw IOException? It seems we can't use this degisn structure due to the template method throw exception but overrided method not throw it. but if change the overrided method to throw it, will cause other subclass both throw it. So can any good suggestion for this case? abstract class DigestComputor{ String compute(DigestAlgorithm algorithm){ MessageDigest instance; try { instance = MessageDigest.getInstance(algorithm.toString()); updateMessageDigest(instance); return hex(instance.digest()); } catch (NoSuchAlgorithmException e) { LOG.error(e.getMessage(), e); throw new UnsupportedOperationException(e.getMessage(), e); } } abstract void updateMessageDigest(MessageDigest instance); } class ByteBufferDigestComputor extends DigestComputor{ private final ByteBuffer byteBuffer; public ByteBufferDigestComputor(ByteBuffer byteBuffer) { super(); this.byteBuffer = byteBuffer; } @Override void updateMessageDigest(MessageDigest instance) { instance.update(byteBuffer); } } class InputStreamDigestComputor extends DigestComputor{ // this place has error. due to exception. if I change the overrided method to throw it. evey caller will handle the exception. but @Override void updateMessageDigest(MessageDigest instance) { throw new IOException(); } }

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• EventAggregator, is it thread-safe?

  - by pfaz

  Is this thread-safe? The EventAggregator in Prism is a very simple class with only one method. I was surprised when I noticed that there was no lock around the null check and creation of a new type to add to the private _events collection. If two threads called GetEvent simultaneously for the same type (before it exists in _events) it looks like this would result in two entries in the collection. /// <summary> /// Gets the single instance of the event managed by this EventAggregator. Multiple calls to this method with the same <typeparamref name="TEventType"/> returns the same event instance. /// </summary> /// <typeparam name="TEventType">The type of event to get. This must inherit from <see cref="EventBase"/>.</typeparam> /// <returns>A singleton instance of an event object of type <typeparamref name="TEventType"/>.</returns> public TEventType GetEvent<TEventType>() where TEventType : EventBase { TEventType eventInstance = _events.FirstOrDefault(evt => evt.GetType() == typeof(TEventType)) as TEventType; if (eventInstance == null) { eventInstance = Activator.CreateInstance<TEventType>(); _events.Add(eventInstance); } return eventInstance; }

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• Getting "prompt aborted by user" javascript exception

  - by Bhagwat

  I am getting "Components.Exception("prompt aborted by user", Cr.NS_ERROR_NOT_AVAILABLE)" exception when I am using "windows.location.href" in javasacript. My Code is: function checkCookie(){ var value = null; var cookieName='UserDetailsCookie'; value=ReadCookie(cookieName); if(value != null){ var url='<%=request.getContextPath()%>/jsp/admin.jsp'; window.location.href = url; } document.loginForm.userName.focus(); } function ReadCookie(name) { name += '='; var parts = document.cookie.split(/;\s*/); for (var i = 0; i < parts.length; i++) { var part = parts[i]; if (part.indexOf(name) == 0) return part.substring(name.length); } return null; } and I am calling this method on onLoad event of body <body onLoad="javascript:checkCookie();"> In anyone knows why this exception throws please?

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• efficient thread-safe singleton in C++

  - by user168715

  The usual pattern for a singleton class is something like static Foo &getInst() { static Foo *inst = NULL; if(inst == NULL) inst = new Foo(...); return *inst; } However, it's my understanding that this solution is not thread-safe, since 1) Foo's constructor might be called more than once (which may or may not matter) and 2) inst may not be fully constructed before it is returned to a different thread. One solution is to wrap a mutex around the whole method, but then I'm paying for synchronization overhead long after I actually need it. An alternative is something like static Foo &getInst() { static Foo *inst = NULL; if(inst == NULL) { pthread_mutex_lock(&mutex); if(inst == NULL) inst = new Foo(...); pthread_mutex_unlock(&mutex); } return *inst; } Is this the right way to do it, or are there any pitfalls I should be aware of? For instance, are there any static initialization order problems that might occur, i.e. is inst always guaranteed to be NULL the first time getInst is called?

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• Connecting to database suddenly started throwing exception for my website

  - by Nirvan

  I have an MVC3 application hosted by third party hosting provider. The site has been running well for the past 3 months without any problems. Today suddenly the Application started throwing following Exception as recorded in my logs part of which is shown below. System.Data.ProviderIncompatibleException: The provider did not return a ProviderManifestToken string. --- System.Data.SqlClient.SqlException: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. The message is self explanatory and I first thought I should increase the connect timeout, but then the exception was still thrown suggesting the other part (Server Not Responding). I contacted my hosting provider and he said there was nothing wrong on his part. So I am stuck with a down website and don't know what to do. Any ideas why the provider is throwing the exception listed above. Also, is it possible for me to remotely connect to the database on the hosting server with limited authority. Any tools for that ? I don't have an exposure in database subject, except for application programming. regards, Nirvan

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• ThreadExceptionEventHandler and invoking delegates

  - by QmunkE

  If I assign a ThreadExceptionEventHandler to Application.ThreadException, why when I invoke a delegate method using a control on the main application thread are any exceptions thrown by that delegate not triggering the event handler? i.e. static void Main() { ... Application.ThreadException += new System.Threading.ThreadExceptionEventHandler(Application_ThreadException); Application.Run(new Form1()); } static void Application_ThreadException(object sender, System.Threading.ThreadExceptionEventArgs e) { Console.Error.Write("A thread exception occurred!"); } ... private void Form1_Load(object sender, EventArgs e) { Thread syncThread = new Thread(new ThreadStart(this.ThrowException)); syncThread.Start(); } private void ThrowException() { button1.Invoke(new MethodInvoker(delegate { // Not handled by ThreadExceptionEventHandler? throw new Exception(); })); } The context on this is that I have a background thread started from a form which is throwing an unhandled exception which terminates the application. I know this thread is going to be unreliable since it is network connectivity reliant and so subject to being terminated at any point, but I'm just interested as to why this scenario doesn't play out as I expect?

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

  - by Ian Boyd

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

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• boost::asio::io_service throws exception

  - by Ace

  Okay, I seriously cannot figure this out. I have a DLL project in MSVC that is attempting to use Asio (from Boost 1.45.0), but whenever I create my io_service, an exception is thrown. Here is what I am doing for testing purposes: void run() { boost::this_thread::sleep(boost::posix_time::seconds(5)); try { boost::asio::io_service io_service; } catch (std::exception & e) { MessageBox(NULL, e.what(), "Exception", MB_OK); } } BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved) { if (fdwReason == DLL_PROCESS_ATTACH) { boost::thread thread(run); } return TRUE; } This is what the message box shows: winsock: WSAStartup cannot function at this time because the underlying system it uses to provide network services is currently unavailable Here is what MSDN says about it (error code 10091, WSASYSNOTREADY): Network subsystem is unavailable. This error is returned by WSAStartup if the Windows Sockets implementation cannot function at because the underlying system it uses to provide network services is currently unavailable. Users should check: That the appropriate Windows Sockets DLL file is in the current path. That they are not trying to use more than one Windows Sockets implementation simultaneously. If there is more than one Winsock DLL on your system, be sure the first one in the path is appropriate for the network subsystem currently loaded. The Windows Sockets implementation documentation to be sure all necessary components are currently installed and configured correctly. Yet none of this seems to apply to me (or so I think). Here is my command line: /O2 /GL /D "_WIN32_WINNT=0x0501" /D "_WINDLL" /FD /EHsc /MD /Gy /Fo"Release\" /Fd"Release\vc90.pdb" /W3 /WX /nologo /c /TP /errorReport:prompt If anyone knows what might be wrong, please help me out! Thanks.

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• Safe json parsing with jquery?

  - by user246114

  Hi, I am using jquery with json. My client pages generate json, which I store on my server. The clients can then fetch the json back out later, parse, and show it. Since my clients are generating the json, it may not be safe. I think jquery uses eval() internally. Is that true? Is there a way to use the native json parsers from the browsers where available, otherwise fall back to manual parsing if not? I'm new to jquery so I don't know where I'd insert my own parsing code. I'm doing something like: $.ajax({ url: 'myservlet', type: 'GET', dataType: 'json', timeout: 1000, error: function(){ alert('Error loading JSON'); }, success: function(json){ alert("It worked!: " + json.name + ", " + json.grade); } }); so in the success() method, the json object is already parsed for me. Is there a way to catch it as a raw string first? Then I can decide whether to use the native parsers or manual parsing (hoping there's a jquery plugin for that..). The articles I'm reading are all from different years, so I don't know if jquery has already abandoned eval() already for json, Thank you

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• Thread-Safe lazy instantiating using MEF

  - by Xaqron

  // Member Variable private static readonly object _syncLock = new object(); // Now inside a static method foreach (var lazyObject in plugins) { if ((string)lazyObject.Metadata["key"] = "something") { lock (_syncLock) { // It seems the `IsValueCreated` is not up-to-date if (!lazyObject.IsValueCreated) lazyObject.value.DoSomething(); } return lazyObject.value; } } Here I need synchronized access per loop. There are many threads iterating this loop and based on the key they are looking for, a lazy instance is created and returned. lazyObject should not be created more that one time. Although Lazy class is for doing so and despite of the used lock, under high threading I have more than one instance created (I track this with a Interlocked.Increment on a volatile static int and log it somewhere). The problem is I don't have access to definition of Lazy and MEF defines how the Lazy class create objects. I should notice the CompositionContainer has a thread-safe option in constructor which is already used. My questions: 1) Why the lock doesn't work ? 2) Should I use an array of locks instead of one lock for performance improvement ?

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• Is this function thread-safe?

  - by kiddo

  Hello all,I am learning multi-threading and for the sake of understanding I have wriiten a small function using multithreading...it works fine.But I just want to know if that thread is safe to use,did I followed the correct rule. void CThreadingEx4Dlg::OnBnClickedOk() { //in thread1 100 elements are copied to myShiftArray(which is a CStringArray) thread1 = AfxBeginThread((AFX_THREADPROC)MyThreadFunction1,this); WaitForSingleObject(thread1->m_hThread,INFINITE); //thread2 waits for thread1 to finish because thread2 is going to make use of myShiftArray(in which thread1 processes it first) thread2 = AfxBeginThread((AFX_THREADPROC)MyThreadFunction2,this); thread3 = AfxBeginThread((AFX_THREADPROC)MyThreadFunction3,this); } UINT MyThreadFunction1(LPARAM lparam) { CThreadingEx4Dlg* pthis = (CThreadingEx4Dlg*)lparam; pthis->MyFunction(0,100); return 0; } UINT MyThreadFunction2(LPARAM lparam) { CThreadingEx4Dlg* pthis = (CThreadingEx4Dlg*)lparam; pthis->MyCommonFunction(0,20); return 0; } UINT MyThreadFunction3(LPARAM lparam) { CThreadingEx4Dlg* pthis = (CThreadingEx4Dlg*)lparam; WaitForSingleObject(pthis->thread3->m_hThread,INFINITE); //here thread3 waits for thread 2 to finish so that thread can continue pthis->MyCommonFunction(21,40); return 0; } void CThreadingEx4Dlg::MyFunction(int minCount,int maxCount) { for(int i=minCount;i<maxCount;i++) { //assume myArray is a CStringArray and it has 100 elemnts added to it. //myShiftArray is a CStringArray -public to the class CString temp; temp = myArray.GetAt(i); myShiftArray.Add(temp); } } void CThreadingEx4Dlg::MyCommonFunction(int min,int max) { for(int i = min;i < max;i++) { CSingleLock myLock(&myCS,TRUE); CString temp; temp = myShiftArray.GetAt(i); //threadArray is CStringArray-public to the class threadArray.Add(temp); } myEvent.PulseEvent(); }

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• safe structures embedded systems

  - by user405633

  I have a packet from a server which is parsed in an embedded system. I need to parse it in a very efficient way, avoiding memory issues, like overlapping, corrupting my memory and others variables. The packet has this structure "String A:String B:String C". As example, here the packet received is compounded of three parts separated using a separator ":", all these parts must be accesibles from an structure. Which is the most efficient and safe way to do this. A.- Creating an structure with attributes (partA, PartB PartC) sized with a criteria based on avoid exceed this sized from the source of the packet, and attaching also an index with the length of each part in a way to avoid extracting garbage, this part length indicator could be less or equal to 300 (ie: part B). typedef struct parsedPacket_struct { char partA[2];int len_partA; char partB[300];int len_partB; char partC[2];int len_partC; }parsedPacket; The problem here is that I am wasting memory, because each structure should copy the packet content to each the structure, is there a way to only save the base address of each part and still using the len_partX.

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• fgets throwing unhandled exception while parsing stl

  - by user3478400

  I am new to c++, I am trying to parse a stl file which is of about 64MB and has about ~18K lines in it. The code works fine for first few 100 lines but then fgets throws following exception: "Unhandled exception at 0x77B0BAC5 (ntdll.dll) in STLparser.exe: 0xC0000024: There is a mismatch between the type of object required by the requested operation and the type of object that is specified in the request." I have checked manually the line for which fgets throws exception, there is nothing out of ordinary there. I am out of options for now. Any help to fix this issue will be greatly appreciated. ================CODE========================== #include<fstream> #include<iostream> #include"ParseString.h" #include"Vectors.h" using namespace std; int main(void) { //Define variables FILE *file; char *line = new char; parsestring oneline; int n_Vols = 0, n_Elms = 0, n_nods = -1, E = 0; Nod *nodes = new Nod(); Nod dummy; Elm *elements = new Elm(); int mycounter = 0; //Open file fopen_s(&file, "sample.stl", "r"); while (fgets(line, 1024, file) != NULL) //**********Getting Error Here************* { // populate required data } fclose(file); printf("%d,%d,%d", n_Vols, n_Elms, n_nods); getchar(); return 0; } ===================When broken, execution resumes at this function (not my function, something internal) void __cdecl _unlock ( int locknum ) { /* * leave the critical section. */ LeaveCriticalSection( _locktable[locknum].lock ); }

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• nothrow or exception ?

  - by Muggen

  I am a student and I have small knowledge on C++, which I try to expand. This is more of a philosophical question.. I am not trying to implement something. Since #include <new> //... T * t = new (std::nothrow) T(); if(t) { //... } //... Will hide the Exception, and since dealing with Exceptions is heavier compared to a simple if(t), why isn't the normal new T() not considered less good practice, considering we will have to use try-catch() to check if a simple allocation succeeded (and if we don't, just watch the program die)?? What are the benefits (if any) of the normal new allocation compared to using a nothrow new? Exception's overhead in that case is insignificant ? Also, Assume that an allocation fails (eg. no memory exists in the system). Is there anything the program can do in that situation, or just fail gracefully. There is no way to find free memory on the heap, when all is reserved, is there? Incase an allocation fails, and an std::bad_alloc is thrown, how can we assume that since there is not enough memory to allocate an object (Eg. a new int), there will be enough memory to store an exception ?? Thanks for your time. I hope the question is in line with the rules.

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• Null safe way to get values from an IDataReader

  - by kumar

  Hi all, (LocalVariable)ABC.string(Name)= (Idatareader)datareader.GetString(0); this name value is coming from database.. what happening here is if this name value is null while reading it's throwing an exception? I am manually doing some if condition here. I don't want to write a manual condition to check all my variables.. I am doing something like this now.. string abc = (Idatareader)datareader.GetValue(0); if(abc = null) //assiging null else assiging abc value is there something like can we write extension method for this? thanks

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• Making swap faster, easier to use and exception-safe

  - by FredOverflow

  I could not sleep last night and started thinking about std::swap. Here is the familiar C++98 version: template <typename T> void swap(T& a, T& b) { T c(a); a = b; b = c; } If a user-defined class Foo uses external ressources, this is inefficient. The common idiom is to provide a method void Foo::swap(Foo& other) and a specialization of std::swap<Foo>. Note that this does not work with class templates since you cannot partially specialize a function template, and overloading names in the std namespace is illegal. The solution is to write a template function in one's own namespace and rely on argument dependent lookup to find it. This depends critically on the client to follow the "using std::swap idiom" instead of calling std::swap directly. Very brittle. In C++0x, if Foo has a user-defined move constructor and a move assignment operator, providing a custom swap method and a std::swap<Foo> specialization has little to no performance benefit, because the C++0x version of std::swap uses efficient moves instead of copies: #include <utility> template <typename T> void swap(T& a, T& b) { T c(std::move(a)); a = std::move(b); b = std::move(c); } Not having to fiddle with swap anymore already takes a lot of burden away from the programmer. Current compilers do not generate move constructors and move assignment operators automatically yet, but as far as I know, this will change. The only problem left then is exception-safety, because in general, move operations are allowed to throw, and this opens up a whole can of worms. The question "What exactly is the state of a moved-from object?" complicates things further. Then I was thinking, what exactly are the semantics of std::swap in C++0x if everything goes fine? What is the state of the objects before and after the swap? Typically, swapping via move operations does not touch external resources, only the "flat" object representations themselves. So why not simply write a swap template that does exactly that: swap the object representations? #include <cstring> template <typename T> void swap(T& a, T& b) { unsigned char c[sizeof(T)]; memcpy( c, &a, sizeof(T)); memcpy(&a, &b, sizeof(T)); memcpy(&b, c, sizeof(T)); } This is as efficient as it gets: it simply blasts through raw memory. It does not require any intervention from the user: no special swap methods or move operations have to be defined. This means that it even works in C++98 (which does not have rvalue references, mind you). But even more importantly, we can now forget about the exception-safety issues, because memcpy never throws. I can see two potential problems with this approach: First, not all objects are meant to be swapped. If a class designer hides the copy constructor or the copy assignment operator, trying to swap objects of the class should fail at compile-time. We can simply introduce some dead code that checks whether copying and assignment are legal on the type: template <typename T> void swap(T& a, T& b) { if (false) // dead code, never executed { T c(a); // copy-constructible? a = b; // assignable? } unsigned char c[sizeof(T)]; std::memcpy( c, &a, sizeof(T)); std::memcpy(&a, &b, sizeof(T)); std::memcpy(&b, c, sizeof(T)); } Any decent compiler can trivially get rid of the dead code. (There are probably better ways to check the "swap conformance", but that is not the point. What matters is that it's possible). Second, some types might perform "unusual" actions in the copy constructor and copy assignment operator. For example, they might notify observers of their change. I deem this a minor issue, because such kinds of objects probably should not have provided copy operations in the first place. Please let me know what you think of this approach to swapping. Would it work in practice? Would you use it? Can you identify library types where this would break? Do you see additional problems? Discuss!

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• Do we really need a safe release macro?

  - by Ian1971

  Quite a lot of people seem to use a macro such as #define SAFE_RELEASE(X) [X release]; X = nil; (myself included). I've been reassessing why I am using it and wanted to canvas some opinion. The purpose (I think) for using this macro is so that if you were to accidentally use your object after releasing it then you won't get a bad access exception because objective-c will quite happily ignore it when the object is nil. It strikes me that this has the potential to mask some obscure bugs. Maybe it would actually be preferable for the program to crash when you try to use X again. That way during testing you can find the issue and improve the code. Does this macro encourage lazy programming? Thoughts?

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• Facing Null Pointer Exception while using BIRT

  - by srikanth

  Hi, I am using BIRT APIs in a java program.My code is : package com.tecnotree.mdx.product.utils; import java.util.HashMap; import java.util.logging.Level; import org.eclipse.birt.core.exception.BirtException; import org.eclipse.birt.core.framework.Platform; import org.eclipse.birt.report.engine.api.EngineConfig; import org.eclipse.birt.report.engine.api.EngineConstants; import org.eclipse.birt.report.engine.api.HTMLRenderOption; import org.eclipse.birt.report.engine.api.IReportEngine; import org.eclipse.birt.report.engine.api.IReportEngineFactory; import org.eclipse.birt.report.engine.api.IReportRunnable; import org.eclipse.birt.report.engine.api.IRunAndRenderTask; import org.eclipse.birt.report.engine.api.ReportEngine; public class ExampleReport { public static void main(String[] args) { // Variables used to control BIRT Engine instance ReportEngine eng = null; IReportRunnable design = null; IRunAndRenderTask task = null; HTMLRenderOption renderContext = null; HashMap contextMap = null; HTMLRenderOption options = null; final EngineConfig conf = new EngineConfig(); conf .setEngineHome("C:\\birt-runtime-2_5_2\\birt-runtime-2_5_2\\ReportEngine"); System.out.println("conf " + conf.getBIRTHome()); conf.setLogConfig(null, Level.FINE); try { Platform.startup(conf); } catch (BirtException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } IReportEngineFactory factory = (IReportEngineFactory) Platform .createFactoryObject(IReportEngineFactory.EXTENSION_REPORT_ENGINE_FACTORY); System.out.println("Factory : " + factory.toString()); System.out.println(conf.toString()); IReportEngine engine = factory.createReportEngine(conf); System.out.println("Engine : " + engine); try { design = eng .openReportDesign("C:\\birt-runtime-2_5_2\\birt-runtime-2_5_2\\ReportEngine\\samples\\hello_world.rptdesign"); } catch (Exception e) { System.err .println("An error occured during the opening of the report file!"); e.printStackTrace(); System.exit(-1); } task = eng.createRunAndRenderTask(design); renderContext = new HTMLRenderOption(); renderContext.setImageDirectory("image"); contextMap = new HashMap(); contextMap.put(EngineConstants.APPCONTEXT_HTML_RENDER_CONTEXT, renderContext); task.setAppContext(contextMap); options = new HTMLRenderOption(); options.setOutputFileName("c:/temp/output.html"); options.setOutputFormat("html"); task.setRenderOption(options); try { task.run(); } catch (Exception e) { System.err.println("An error occured while running the report!"); e.printStackTrace(); System.exit(-1); } System.out.println("All went well. Closing program!"); eng.destroy(); } } But i am facing NullPointerException while creating the report. STACKTRACE : Exception in thread "main" java.lang.NullPointerException at org.eclipse.birt.report.engine.api.impl.ReportEngine$EngineExtensionManager.<init>(ReportEngine.java:784) at org.eclipse.birt.report.engine.api.impl.ReportEngine.<init>(ReportEngine.java:109) at org.eclipse.birt.report.engine.api.impl.ReportEngineFactory$1.run(ReportEngineFactory.java:18) at org.eclipse.birt.report.engine.api.impl.ReportEngineFactory$1.run(ReportEngineFactory.java:1) at java.security.AccessController.doPrivileged(Native Method) at org.eclipse.birt.report.engine.api.impl.ReportEngineFactory.createReportEngine(ReportEngineFactory.java:14) at com.tecnotree.mdx.product.utils.ExampleReport.main(ExampleReport.java:47) Please help me regarding this... my project deadline has been reached... Appreciate your Reply Thanks in Advance

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• protobuf-net: incorrect wire-type exception deserializing Guid properties

  - by Paul Smith

  I'm having issues deserializing certain Guid properties of ORM-generated entities using protobuf-net. Here's a simplified example of the code (reproduces most elements of the scenario, but doesn't reproduce the behavior; I can't expose our internal entities, so I'm looking for clues to account for the exception). Say I have a class, Account with an AccountID read-only guid, and an AccountName read-write string. I serialize & immediately deserialize a clone. Deserializing throws an Incorrect wire-type deserializing Guid exception while deserializing. Here's example usage... Account acct = new Account() { AccountName = "Bob's Checking" }; Debug.WriteLine(acct.AccountID.ToString()); using (MemoryStream ms = new MemoryStream()) { ProtoBuf.Serializer.Serialize<Account>(ms, acct); Debug.WriteLine(Encoding.UTF8.GetString(ms.GetBuffer())); ms.Position = 0; Account clone = ProtoBuf.Serializer.Deserialize<Account>(ms); Debug.WriteLine(clone.AccountID.ToString()); } And here's an example ORM'd class (simplified, but demonstrates the relevant semantics I can think of). Uses a shell game to deserialize read-only properties by exposing the backing field ("can't write" essentially becomes "shouldn't write," but we can scan code for instances of assigning to these fields, so the hack works for our purposes). Again, this does not reproduce the exception behavior; I'm looking for clues as to what could: [DataContract()] [Serializable()] public partial class Account { public Account() { _accountID = Guid.NewGuid(); } [XmlAttribute("AccountID")] [DataMember(Name = "AccountID", Order = 1)] public Guid _accountID; /// <summary> /// A read-only property; XML, JSON and DataContract serializers all seem /// to correctly recognize the public backing field when deserializing: /// </summary> [IgnoreDataMember] [XmlIgnore] public Guid AccountID { get { return this._accountID; } } [IgnoreDataMember] protected string _accountName; [DataMember(Name = "AccountName", Order = 2)] [XmlAttribute] public string AccountName { get { return this._accountName; } set { this._accountName = value; } } } XML, JSON and DataContract serializers all seem to serialize / deserialize these object graphs just fine, so the attribute arrangement basically works. I've tried protobuf-net with lists vs. single instances, different prefix styles, etc., but still always get the 'incorrect wire-type ... Guid' exception when deserializing. So the specific questions is, is there any known explanation / workaround for this? I'm at a loss trying to trace what circumstances (in the real code but not the example) could be causing it. We hope not to have to create a protobuf dependency directly in the entity layer; if that's the case, we'll probably create proxy DTO entities with all public properties having protobuf attributes. (This is a subjective issue I have with all declarative serialization models; it's a ubiquitous pattern & I understand why it arose, but IMO, if we can put a man on the moon, then "normal" should be to have objects and serialization contracts decoupled. ;-) ) Thanks!

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• HTTP Bad Request error when requesting a WCF service contract

  - by Enrico Campidoglio

  I have a WCF service with the following configuration: <system.serviceModel> <behaviors> <serviceBehaviors> <behavior name="MetadataEnabled"> <serviceDebug includeExceptionDetailInFaults="true" /> <serviceMetadata httpGetEnabled="true" /> </behavior> </serviceBehaviors> </behaviors> <services> <service behaviorConfiguration="MetadataEnabled" name="MyNamespace.MyService"> <endpoint name="BasicHttp" address="" binding="basicHttpBinding" contract="MyNamespace.IMyServiceContract" /> <endpoint name="MetadataHttp" address="contract" binding="mexHttpBinding" contract="IMetadataExchange" /> <host> <baseAddresses> <add baseAddress="http://localhost/myservice" /> </baseAddresses> </host> </service> </services> </system.serviceModel> When hosting the service in the WcfSvcHost.exe process, if I browse to the URL: http://localhost/myservice/contract where the service metadata is available I get an HTTP 400 Bad Request error. By inspecting the WCF logs I found out that an System.Xml.XmlException exception is being thrown with the message: "The body of the message cannot be read because it is empty."Here is an extract of the log file: <Exception> <ExceptionType> System.ServiceModel.ProtocolException, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 </ExceptionType> <Message>There is a problem with the XML that was received from the network. See inner exception for more details.</Message> <StackTrace> at System.ServiceModel.Channels.HttpRequestContext.CreateMessage() at System.ServiceModel.Channels.HttpChannelListener.HttpContextReceived(HttpRequestContext context, ItemDequeuedCallback callback) at System.ServiceModel.Channels.SharedHttpTransportManager.OnGetContextCore(IAsyncResult result) at System.ServiceModel.Channels.SharedHttpTransportManager.OnGetContext(IAsyncResult result) at System.ServiceModel.Diagnostics.Utility.AsyncThunk.UnhandledExceptionFrame(IAsyncResult result) at System.Net.LazyAsyncResult.Complete(IntPtr userToken) at System.Net.LazyAsyncResult.ProtectedInvokeCallback(Object result, IntPtr userToken) at System.Net.ListenerAsyncResult.WaitCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* nativeOverlapped) at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP) </StackTrace> <InnerException> <ExceptionType>System.Xml.XmlException, System.Xml, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</ExceptionType> <Message>The body of the message cannot be read because it is empty.</Message> <StackTrace> at System.ServiceModel.Channels.HttpRequestContext.CreateMessage() at System.ServiceModel.Channels.HttpChannelListener.HttpContextReceived(HttpRequestContext context, ItemDequeuedCallback callback) at System.ServiceModel.Channels.SharedHttpTransportManager.OnGetContextCore(IAsyncResult result) at System.ServiceModel.Channels.SharedHttpTransportManager.OnGetContext(IAsyncResult result) at System.ServiceModel.Diagnostics.Utility.AsyncThunk.UnhandledExceptionFrame(IAsyncResult result) at System.Net.LazyAsyncResult.Complete(IntPtr userToken) at System.Net.LazyAsyncResult.ProtectedInvokeCallback(Object result, IntPtr userToken) at System.Net.ListenerAsyncResult.WaitCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* nativeOverlapped) at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP) </StackTrace> </InnerException> </Exception> If I instead browse to the URL: http://localhost/myservice?wsdl everything works just fine and I get the WSDL contract. At this point, I can also remove the "MetadataHttp" metadata endpoint completely, and it wouldn't make any difference. I'm using .NET 3.5 SP1. Does anyone have an idea of what could be wrong here?

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