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  • What to do when ServerSocket throws IOException and keeping server running

    - by s5804
    Basically I want to create a rock solid server. while (keepRunning.get()) { try { Socket clientSocket = serverSocket.accept(); ... spawn a new thread to handle the client ... } catch (IOException e) { e.printStackTrace(); // NOW WHAT? } } In the IOException block, what to do? Is the Server socket at fault so it need to be recreated? For example wait a few seconds and then serverSocket = ServerSocketFactory.getDefault().createServerSocket(MY_PORT); However if the server socket is still OK, then it is a pity to close it and kill all previously accepted connections that are still communicating. EDIT: After some answers, here my attempt to deal with the IOException. Would the implementation be guaranteeing keeping the server up and only re-create server socket when only necessary? while (keepRunning.get()) { try { Socket clientSocket = serverSocket.accept(); ... spawn a new thread to handle the client ... bindExceptionCounter = 0; } catch (IOException e) { e.printStackTrace(); recreateServerSocket(); } } private void recreateServerSocket() { while (keepRunning) { try { logger.info("Try to re-create Server Socket"); ServerSocket socket = ServerSocketFactory.getDefault().createServerSocket(RateTableServer.RATE_EVENT_SERVER_PORT); // No exception thrown, then use the new socket. serverSocket = socket; break; } catch (BindException e) { logger.info("BindException indicates that the server socket is still good.", e); bindExceptionCounter++; if (bindExceptionCounter < 5) { break; } } catch (IOException e) { logger.warn("Problem to re-create Server Socket", e); e.printStackTrace(); try { Thread.sleep(30000); } catch (InterruptedException ie) { logger.warn(ie); } } } }

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  • NullPointerException when trying to add an object to a PriorityQueue

    - by meagan
    i keep getting a null pointer exception when trying to add an object to a priority queue i initialize the queue: private PriorityQueue<NodeObject> nodes; and here i try to add to it: NodeObject childNode = new NodeObject(child, 1); nodes.add(childNode); why doesn't this work? i know my NodeObject is not null because i create it right before i add it.

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  • ExecutionException and InterruptedException while using Future class's get() method

    - by java_geek
    ExecutorService executor = Executors.newSingleThreadExecutor(); try { Task t = new Task(response,inputToPass,pTypes,unit.getInstance(),methodName,unit.getUnitKey()); Future<SCCallOutResponse> fut = executor.submit(t); response = fut.get(unit.getTimeOut(),TimeUnit.MILLISECONDS); } catch (TimeoutException e) { // if the task is still running, a TimeOutException will occur while fut.get() cat.error("Unit " + unit.getUnitKey() + " Timed Out"); response.setVote(SCCallOutConsts.TIMEOUT); } catch (InterruptedException e) { cat.error(e); } catch (ExecutionException e) { cat.error(e); } finally { executor.shutdown(); } } How should i handle the InterruptedException and ExecutionException in the code? And in what cases are these exceptions thrown?

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  • How do i change this method to get strings instead of ints

    - by David
    here is the original code: public static int getInt () { Scanner in = new Scanner (System.in) ; if (in.hasNextInt()) { int a = in.nextInt() ; return a ; } else { System.out.println ("try again:") ; return getInt () ; } } This checks and sees if the input it receives is an int. If it is then it returns the int, if not it tells you to try again and re-runs. This is what i tried to do to change it: public static String getIns () { Scanner in = new Scanner (System.in) ; if (in.hasNextString()) { String a = in.nextString() ; return a ; } else { System.out.println ("try again:") ; return getIns () ; } } This doesn't work though. I looked through the documentation for the scanner class and i think the problem is that there is no such method as in.hasNextString or in.nextString What methods from the scanner class can i use to do what i intend these to do?

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  • JSF 2.0 method invocation with argument from var of dataGrid

    - by little_b
    Hello I use primefaces with facelets and i have a quastion: for example i have dataGrid and i want to call method of bean, that registered in faces-config, to include some dynamic content: <p:dataGrid var="provider" value="#{paymentFormBean.providers}"> <ui:include src="contentFactory.getSpecificForm('some attribute')"/> </p:dataGrid> How could i invoke getSpecificForm method with argument from var of dataGrid? Something like: <p:dataGrid var="provider" value="#{paymentFormBean.providers}"> <ui:include src="contentFactory.getSpecificForm(provider.formName)"/> </p:dataGrid> Could anyone help me? Thank you

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  • Retrieve only the superclass from a class hierarchy

    - by user1792724
    I have an scenario as the following: @Entity @Table(name = "ANIMAL") @Inheritance(strategy = InheritanceType.JOINED) public class Animal implements Serializable { @Id @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "S_ANIMAL") @SequenceGenerator(name = "S_ANIMAL", sequenceName = "S_ANIMAL", allocationSize = 1) public int getNumero() { return numero; } public void setNumero(int numero) { this.numero = numero; } . . . } and as the subclass: @Entity @Table(name = "DOG") public class Dog extends Animal { private static final long serialVersionUID = -7341592543130659641L; . . . } I have a JPA Select statement like this: SELECT a FROM Animal a; I'm using Hibernate 3.3.1 As I can see the framework retrieves instances of Animal and also of Dog using a left outer join. Is there a way to Select only the "part" Animal? I mean, the previous Select will get all the Animals, those that are only Animals but not Dogs and those that are Dogs. I want them all, but in the case of Dogs I want to only retrieve the "Animal part" of them. I found the @org.hibernate.annotations.Entity(polymorphism = PolymorphismType.EXPLICIT) but as I could see this only works if Animal isn't an @Entity. Thanks a lot.

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  • Servlet request getparameter's performance

    - by Bob
    Hi, I noticed that my app is very slow sometimes, so I've done some tests. It's a very simple web app. One servlet gets some parameters than stores them. Everything's fine except one thing. It takes too long to get a parameter for the first time. It doesn't matter which parameter I try to get, but for the first time it is very slow. The strange thing is this doesn't happen always. Sometimes getting a parameter for the first time is not slow. My code looks like this request.getParameter("paramName"); request.getParameter("paramName2"); request.getParameter("paramName3"); Getting "paramName" is slow. Getting the others is very fast. By slow I mean : 200-800 millisec By very fast I mean: ~0 millisec (in the code snippet, I didn't write the performance test, but I'm using System.currentTimeMillis())

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  • Junit exception test

    - by Prithis
    I have two tests to check the expected exception throw. I am using Junit 4 and has following syntax. @Test(expected=IllegalArgumentException.class) public void testSomething(){ .......... } One of the tests fail even though IllegalArgumentException is thrown and the other passes. Any idea whats missing?? I modified the test which is failing to following and it passes. public void testSomething(){ try{ ............ //line that throws exception fail(); }catch(IllegalArgumentException e) { } }

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  • How to find the Mac address of a 'shutdown' system on local lan (is it possible?)

    - by pirates-iiita
    hello everyone, Can anyone please tell the way to find out the mac address of a system which is: Shutdown Power plugged in Connected to Lan Nic card ON. Kindly post the solution as i urgently need it in my project... thank you Update I am asking how to find out the mac address of some other system which is already shutdown.... and which is on lan.. I want to find out its mac from my system.... and to be clear... i want to tell that.. arp table can be populated by using ping .. i.e. if 172.16.3.12 is not in arp table then it can be added by just ping 172.16.3.12 but a system can be pinged only if its on ... a shutdown system can't be pinged...

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  • NetBeans open project problem.

    - by rgksugan
    I created a NetBeans project. I took the project folders zipped to another machine and tried opening it in NetBeans. NetBeans didn't identify it as a NetBeans project. I have transfered projects in this way before but why is it not working now? Are any of my project files corrupted. Is there any way to retrieve my files from this?

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  • JTextArea thread safe?

    - by Dhaivat Pandya
    Hello everyone, I have some code that does some initialization (including making a JTextArea object), starts three seperate threads, and then these threads try to update the JTextArea (i.e. append() to it), but its not working at all. Nothing shows up on the JTextArea (however, during the initialzation, I print some test lines onto it, and that works fine). What's going on? How can I fix this? Also, each of those threads sleeps a random amount of time every time it has to update the JTextArea. Sorry I haven't provided any code, its all spread out over several files.

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  • Using thread inter-communication to increase my server app's IO throughput; not sure how

    - by Howard Guo
    My server application creates a new thread for each incoming connection. Incoming requests are serialized in a BlockingQueue. There is one worker thread taking items from the queue, produce a response and send the response through socket. I have noticed a throughput issue: Currently, worker thread is responsible of sending the response message through socket, thus severely wasting processing power and throughput. I am considering: rather than sending the response itself, why not telling network IO threads to send the response? However, when I think about thread inter-communication, I cannot yet figure out how to approach it: Worker thread will produce a response, but how will it inform the response message to IO thread? Is there a standard/best practice? Thank you.

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  • Lackadaisical One-to-One between Char and Byte Streams

    - by Vaibhav Bajpai
    I expected to have a one-to-one correspondence between the character streams and byte streams in terms of how the classes are organized in their hierarchy. FilterReader and FilterWriter (character streams) correspond back to FilterInputStream and FilterOutputStream (byte stream) classes. However I noticed few changes as - BufferedInputStream extends FilterInputStream, but BufferedReader does NOT extend FilterReader. BufferedOutputStream and PrintStream both extend FilterOutputStream, but BufferedWriter and PrintWriter does NOT extend FilterWriter. FilterInputStream and FilterOutputStream are not abstract classes, but FilterReader and FilterWriter are. I am not sure if I am being too paranoid to point out such differences, but was just curious to know if there was design reasoning behind such decision.

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  • How to create new account using servlets

    - by Alvin
    I want to know how can I create new account using servlets in post method? I'm currently following MVC design pattern, and I want to know if I pass the required data to register new account from JSP page, then how can I get that data in post method? As request.getParameter() method returning me null. How can I know that post method is calling to create new account? How can I pass all the relevant user information from servlets to model class for registering data to the database table?

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  • Refactored App Engine project - now Eclipse is infinitely building the project without end

    - by Yog
    I renamed some files in my App Engine project and refactored code, changing references to variables. Everything seemed fine until I changed the references in the web.xml for the project. Then I got a complaint about some error with the DataNucleus enhancer and now the project build process is stuck at 22%. I tried stopping Eclipse and restarting but the build process keeps hanging. Any tips on how to clean out whatever it's getting stuck on?

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  • Client-side framework for web-app with good audio support

    - by Poita_
    I'm trying to create a client-side web app that generates music procedurally using some user-input parameters, so I'm looking for a framework (e.g. Flash, Silverlight etc.) that has the capability to play audio at a specified pitch. Whether it is playing a WAV/MP3 file, using MIDI output, or just playing beeps doesn't really matter -- I just need something that will enable me to generate arbitrary music client-side. I've done a bit of searching and it appears that Flash might have the ability to change pitch with the help of a third-part plugin, but I couldn't find anything similar for Silverlight. I can go a try all them out manually if need be, but I thought I'd ask here first just in case anyone had tried something like this before. Thanks in advance

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  • How to modify my Response.Document XSD for getting author name form Sharepoint

    - by Rohan Patil
    Hi, This is my XSD currently <?xml version="1.0" encoding="Windows-1252"?> <xsd:schema xmlns:tns="urn:Microsoft.Search.Response.Document" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="urn:Microsoft.Search.Response.Document" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <xsd:import namespace="urn:Microsoft.Search.Response.Document.Document" schemaLocation="Microsoft.Search.Response.Document.Document.xsd" /> <xsd:annotation> <xsd:documentation> </xsd:documentation> <xsd:documentation> Defines a Query Respnose from a Windows SharePoint Services 3.0 Query Service. </xsd:documentation> </xsd:annotation> <!-- - - - - - - - - - - - - - - - - - - - - - - - - - --> <!-- Root Element: Document --> <!-- - - - - - - - - - - - - - - - - - - - - - - - - - --> <xsd:element name="Document"> <xsd:complexType> <xsd:sequence> <xsd:element name="Title" type="xsd:string" minOccurs="0" /> <xsd:element name="Action"> <xsd:complexType> <xsd:sequence> <xsd:element name="LinkUrl"> <xsd:complexType> <xsd:simpleContent> <xsd:extension base="xsd:string"> <xsd:attribute name="size" type="xsd:unsignedByte" use="optional" /> <xsd:attribute name="fileExt" type="xsd:string" use="required" /> </xsd:extension> </xsd:simpleContent> </xsd:complexType> </xsd:element> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element name="Description" type="xsd:string" minOccurs="0" /> <xsd:element name="Date" type="xsd:dateTime" minOccurs="0" /> <xsd:element xmlns:q1="urn:Microsoft.Search.Response.Document.Document" ref="q1:Properties" minOccurs="0" /> </xsd:sequence> <xsd:attribute name="relevance" type="xsd:unsignedByte" use="optional" /> </xsd:complexType> </xsd:element> </xsd:schema> I want to able to get the author name.. Please help..

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  • Strange profiling results: definitely non-bottleneck method pops up

    - by jkff
    I'm profiling a program using sampling profiling in YourKit and JProfiler, and also "manually" (I launch it and press Ctrl-Break several times to get thread dumps). All three methods give me extremely strange results: some tens of percents of time spent in a 3-line method that does not even do any allocation or synchronization and doesn't have loops etc. Moreover, after I made this method into a NOP and even removed its invocation completely, the observable program performance didn't change at all (although it got a negligible memory leak, since it was a method for freeing a cheap resource). I'm thinking that this might be because of the constraints that JVM puts on the moments at which a thread's stacktrace may be taken, and it somehow turns out that in my program it is exactly the moments where this method is invoked, although there is absolutely nothing special about it or the context in which it is invoked. What can be the explanation for this phenomenon? What are the aforementioned constraints? What further measurements can I take to clarify the situation?

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  • Spring MVC 3 - How come @ResponseBody method renders a JSTLView?

    - by Ken Chen
    I have mapped one of my method in one Controller to return JSON object by @ResponseBody. @RequestMapping("/{module}/get/{docId}") public @ResponseBody Map<String, ? extends Object> get(@PathVariable String module, @PathVariable String docId) { Criteria criteria = new Criteria("_id", docId); return genericDAO.getUniqueEntity(module, true, criteria); } However, it redirects me to the JSTLView instead. Say, if the {module} is product and {docId} is 2, then in the console I found: DispatcherServlet with name 'xxx' processing POST request for [/xxx/product/get/2] Rendering view [org.springframework.web.servlet.view.JstlView: name 'product/get/2'; URL [/WEB-INF/views/jsp/product/get/2.jsp]] in DispatcherServlet with name 'xxx' How can that be happened? In the same Controller, I have another method similar to this but it's running fine: @RequestMapping("/{module}/list") public @ResponseBody Map<String, ? extends Object> list(@PathVariable String module, @RequestParam MultiValueMap<String, String> params, @RequestParam(value = "page", required = false) Integer pageNumber, @RequestParam(value = "rows", required = false) Integer recordPerPage) { ... return genericDAO.list(module, criterias, orders, pageNumber, recordPerPage); } Above do returns correctly providing me a list of objects I required. Anyone to help me solve the mystery?

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  • apache cxf: multiple endpoint /multipleCXFServlet servlet

    - by robinmag
    Hi, I've a cxf webservice with multiple endpoint. I've succesfully deploy it. The problem is all endpoint's WSDL appear in the same servlet URL. Can i have 2 org.apache.cxf.transport.servlet.CXFServlet servlet in the same web.xml and each servlet serve one endpoint so that i have endpoint1 at http:/locahost/app/endpoint1 and endpoint2 at http:/locahost/app/endpoint2 . Thank you.

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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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