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  • Problem of instanceOf

    - by eric2323223
    Hi, could anyone tell me why this code won't compile? public boolean isOf(Class clazz, Object obj){ if(obj instanceof clazz){ return true; }else{ return false; } } Why I can't pass a class variable to instanceOf? Thanks in advance.

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  • How can I load file into web app through certain periods?

    - by Elena
    Hi all! I have next task: I need to load the same file into my web app several times, for example - twice a day! Suppose in that file I have information, that changes, and I need to load this info into my app to change the statistics for example. How can I load file several times (twice an hour, or twice a day)? What should I use? Is any algorithm to do that? I am not allowed to use external libraries like Quartz Scheduler. So I need to do it with Thread and/or Timer. Can anybody give me some example or algorithm how to do it. Where can I create the entry point to my Thread, can I do it in managed bean or I need some sort of filter/listener/servlet. I works with jsf and richFaces. Maybe in this technologies there are some algorithms to solve my problem. Any ideas? Thanks very much for help!

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  • hibernate column uniqueness question

    - by Seth
    I'm still in the process of learning hibernate/hql and I have a question that's half best practices question/half sanity check. Let's say I have a class A: @Entity public class A { @Id @GeneratedValue(strategy=GenerationType.AUTO) private Long id; @Column(unique=true) private String name = ""; //getters, setters, etc. omitted for brevity } I want to enforce that every instance of A that gets saved has a unique name (hence the @Column annotation), but I also want to be able to handle the case where there's already an A instance saved that has that name. I see two ways of doing this: 1) I can catch the org.hibernate.exception.ConstraintViolationException that could be thrown during the session.saveOrUpdate() call and try to handle it. 2) I can query for existing instances of A that already have that name in the DAO before calling session.saveOrUpdate(). Right now I'm leaning towards approach 2, because in approach 1 I don't know how to programmatically figure out which constraint was violated (there are a couple of other unique members in A). Right now my DAO.save() code looks roughly like this: public void save(A a) throws DataAccessException, NonUniqueNameException { Session session = sessionFactory.getCurrentSession(); try { session.beginTransaction(); Query query = null; //if id isn't null, make sure we don't count this object as a duplicate if(obj.getId() == null) { query = session.createQuery("select count(a) from A a where a.name = :name").setParameter("name", obj.getName()); } else { query = session.createQuery("select count(a) from A a where a.name = :name " + "and a.id != :id").setParameter("name", obj.getName()).setParameter("name", obj.getName()); } Long numNameDuplicates = (Long)query.uniqueResult(); if(numNameDuplicates > 0) throw new NonUniqueNameException(); session.saveOrUpdate(a); session.getTransaction().commit(); } catch(RuntimeException e) { session.getTransaction().rollback(); throw new DataAccessException(e); //my own class } } Am I going about this in the right way? Can hibernate tell me programmatically (i.e. not as an error string) which value is violating the uniqueness constraint? By separating the query from the commit, am I inviting thread-safety errors, or am I safe? How is this usually done? Thanks!

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  • Expandable listview Refreshing

    - by Sam97305421562
    Hi, I am using expandable listview i need to refresh as i am searching the list only for parent.I have searched for tutorial in which i can set visibility only for some parent but not all the expandable listview object . Thanks in advance.

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  • JBoss ignores @RemoteBinding annotation

    - by tputkonen
    I would like to specify JNDI name for an EJB3 bean using annotation, but JBoss 5.1.0 GA seems to ignore the annotation completely. Bean's annotations are: @Remote(Foobar.class) @Stateless(name = "Foobar") @TransactionManagement(TransactionManagementType.BEAN) @RemoteBinding(jndiBinding="ejb/Foobar") public class FoobarBean implements Foobar { ... I tested deploying also using @RemoteBindings annotation, but the result was same: @RemoteBindings({@RemoteBinding(jndiBinding="ejb/Foobar")}) The bean does not get bound to JNDI with the specified name, and the log file doesn't give any clues.

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  • Why does appending "" to a String save memory?

    - by hsmit
    I used a variable with a lot of data in it, say String data. I wanted to use a small part of this string in the following way: this.smallpart = data.substring(12,18); After some hours of debugging (with a memory visualizer) I found out that the objects field smallpart remembered all the data from data, although it only contained the substring. When I changed the code into: this.smallpart = data.substring(12,18)+""; ..the problem was solved! Now my application uses very little memory now! How is that possible? Can anyone explain this? I think this.smallpart kept referencing towards data, but why? UPDATE: How can I clear the big String then? Will data = new String(data.substring(0,100)) do the thing?

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  • JScrollPane Scrolls Down with Long Text in JEditorPane

    - by Jim
    Hello, I want to have a JEditorPane inside a JScrollPane. When the user clicks a button, the click listener will create a textEditor, call jscrollpane.setViewPort(textEditor), call textEditor.setText(String) to fill it with editable text, and call jscrollpane.getVerticalScrollBar().setValue(0). In case you're wondering, yes, the setText() must come after the setViewPort() for reasons that aren't on topic. Here is the problem: After the user clicks the button, the JScrollPane's view scrolls all the way to the bottom. I want the scrollbar to be at the top, as per the last line in my click listener. I popped open a debugger, and to my horror, discovered that the jscrollpane's viewport is being forced down to the bottom after the conclusion of the click listener (when pumping filters). It appears that Swing is delaying the population of the editor/jscrollpane until after the conclusion of the clicklistener, but is calling the scrollbar command first. Thus, the undesired behavior. Anyway, I'm wondering if there is a clean solution. It seems that wanting a scrollpane to be scrolled to the top after modification would be a reasonably common requirement, so I'm assuming this is a well-solved problem. Thanks!

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  • request parameter is taking null value in servlets

    - by Dusk
    Hi, I want to know how can I get the value of the request parameters "j_username" and "j_password"? After successfully login using form based authentication, I want my servlet to get the value of parameters "j_username" and "j_password", but I'm getting null as the value in both parameters. Could anyone please tell me how can I get the actual value of both paramters? Servlets class : package foo; import javax.servlet.http.*; import javax.servlet.*; public class RequestHandler extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) { try { String user = request.getParameter("j_username"); String password = request.getParameter("j_password"); response.getWriter().println(user+" "+password); } catch(Exception e) { e.printStackTrace(); } } } output: null null

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  • Socket server with multiple clients, sending messages to many clients without hurting liveliness

    - by Karl Johanson
    I have a small socket server, and I need to distribute various messages from client-to-client depending on different conditionals. However I think I have a small problem with livelyness in my current code, and is there anything wrong in my approach: public class CuClient extends Thread { Socket socket = null; ObjectOutputStream out; ObjectInputStream in; CuGroup group; public CuClient(Socket s, CuGroup g) { this.socket = s; this.group = g; out = new ObjectOutputStream(this.socket.getOutputStream()); out.flush(); in = new ObjectInputStream(this.socket.getInputStream()); } @Override public void run() { String cmd = ""; try { while (!cmd.equals("client shutdown")) { cmd = (String) in.readObject(); this.group.broadcastToGroup(this, cmd); } out.close(); in.close(); socket.close(); } catch (Exception e) { System.out.println(this.getName()); e.printStackTrace(); } } public void sendToClient(String msg) { try { this.out.writeObject(msg); this.out.flush(); } catch (IOException ex) { } } And my CuGroup: public class CuGroup { private Vector<CuClient> clients = new Vector<CuClient>(); public void addClient(CuClient c) { this.clients.add(c); } void broadcastToGroup(CuClient clientName, String cmd) { Iterator it = this.clients.iterator(); while (it.hasNext()) { CuClient cu = (CuClient)it.next(); cu.sendToClient(cmd); } } } And my main-class: public class SmallServer { public static final Vector<CuClient> clients = new Vector<CuClient>(10); public static boolean serverRunning = true; private ServerSocket serverSocket; private CuGroup group = new CuGroup(); public void body() { try { this.serverSocket = new ServerSocket(1337, 20); System.out.println("Waiting for clients\n"); do { Socket s = this.serverSocket.accept(); CuClient t = new CuClient(s,group); System.out.println("SERVER: " + s.getInetAddress() + " is connected!\n"); t.start(); } while (this.serverRunning); } catch (IOException ex) { ex.printStackTrace(); } } public static void main(String[] args) { System.out.println("Server"); SmallServer server = new SmallServer(); server.body(); } } Consider the example with many more groups, maybe a Collection of groups. If they all synchronize on a single Object, I don't think my server will be very fast. I there a pattern or something that can help my liveliness?

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  • RSA public key exportation

    - by user308806
    Dear all, Here is my code KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA"); KeyPair myPair = kpg.generateKeyPair(); PrivateKey k = myPair.getPrivate(); System.out.print(k.serialVersionUID); Cipher c = Cipher.getInstance("RSA"); c.init(Cipher.ENCRYPT_MODE, myPair.getPublic()); String myMessage = new String("Testing the message"); byte[] bytes = c.doFinal(myMessage.getBytes()); String tt = new String(bytes); System.out.println(tt); Cipher d = Cipher.getInstance("RSA"); d.init(Cipher.DECRYPT_MODE, myPair.getPrivate()); byte[] temp = d.doFinal(bytes); String tst = new String(temp); System.out.println(tst); My question is how can i get the public key and stored elsewhere

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  • how to convert byte array to key format??

    - by sebby_zml
    hi everyone, i would like to know how to convert byte array into key. i am doing an AES encryption/decryption. instead of generating a key, i would like to use my generated byte array. byte[] clientCK = Milenage.f3(sharedSecret16, RANDbytes, opc); let say i have a byte array called clientCK, stated above. i want to use it in AES encryption as shown below. Cipher c = Cipher.getInstance("AES"); c.init(Cipher.ENCRYPT_MODE, key); byte[] encValue = c.doFinal(valueToEnc.getBytes()); String encryptedValue = new BASE64Encoder().encode(encValue); therefore, i need to convert that byte array clientCK into key format. please help.

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  • Unexpected JAXB error

    - by Mark Lewis
    Hello, From the documentation it's clear I need to use the following to get a simple unmarshalling to occur from my XML file/schema: JAXBContext jc = JAXBContext.newInstance("PackageName"); where PackageName is my package name. I've looked on google for a bit to no avail, to find out why I'm then getting this runtime error: Line:Col[2:142]:cvc-elt.1: Cannot find the declaration of element 'myconfig'. Line:Col[2:142]:unexpected element (uri:"http://www.w3.org", local:"myconfig"). Expected elements are <{}myconfig> Caught UnmarshalException This occurs at the top of all my class files, including the ones the XJC plugin for eclipse created for me (which I then moved out of PackageName.PackageName which it automatically created): package PackageName; so why is this error occurring?

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  • best way to pick a random subset from a collection?

    - by Tom
    I have a set of objects in a Vector from which I'd like to select a random subset (e.g. 100 items coming back; pick 5 randomly). In my first (very hasty) pass I did an extremely simple and perhaps overly clever solution: Vector itemsVector = getItems(); Collections.shuffle(itemsVector); itemsVector.setSize(5); While this has the advantage of being nice and simple, I suspect it's not going to scale very well, i.e. Collections.shuffle() must be O(n) at least. My less clever alternative is Vector itemsVector = getItems(); Random rand = new Random(System.currentTimeMillis()); // would make this static to the class List subsetList = new ArrayList(5); for (int i = 0; i < 5; i++) { // be sure to use Vector.remove() or you may get the same item twice subsetList.add(itemsVector.remove(rand.nextInt(itemsVector.size()))); } Any suggestions on better ways to draw out a random subset from a Collection?

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  • Generating equals / hashcode / toString using annotation

    - by Bruno Bieth
    I believe I read somewhere people generating equals / hashcode / toString methods during compile time (using APT) by identifying which fields should be part of the hash / equality test. I couldn't find anything like that on the web (I might have dreamed it ?) ... That could be done like that : public class Person { @Id @GeneratedValue private Integer id; @Identity private String firstName, lastName; @Identity private Date dateOfBirth; //... } For an entity (so we want to exlude some fields, like the id). Or like a scala case class i.e a value object : @ValueObject public class Color { private int red, green, blue; } Not only the file becomes more readable and easier to write, but it also helps ensuring that all the attributes are part of the equals / hashcode (in case you add another attribute later on, without updating the methods accordingly). I heard APT isn't very well supported in IDE but I wouldn't see that as a major issue. After all, tests are mainly run by continuous integration servers. Any idea if this has been done already and if not why ? Thanks

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  • Dependency on Spring's annotations

    - by Jacques René Mesrine
    I have annotated my classes with @Repository, @Resource, @Component, @Service annotations but these classes must run in 2 environments. The first environment is Spring 2.x based while the other has no spring at all. I'm sure the code will fail without the spring jars & I want to know ideas from you on how I can retain the annotations but still work in both environments

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  • Writing a Servlet that checks to see if JSP's exist and forwards to another JSP if they aren't

    - by Omar Kooheji
    I've beeb tasked with writing a servlet that intercepts a call to and JSP in a specific directoy, check that the file exists and if it does just forwarding to that file, if if doesn't I'm to forward to a default JSP. I've setup the web.xml as follows: <servlet> <description>This is the description of my J2EE component</description> <display-name>This is the display name of my J2EE component</display-name> <servlet-name>CustomJSPListener</servlet-name> <servlet-class> ... CustomJSPListener</servlet-class> <load-on-startup>1</load-on-startup> </servlet> ... <servlet-mapping> <servlet-name>CustomJSPListener</servlet-name> <url-pattern>/custom/*</url-pattern> </servlet-mapping> And the doGet method of the servlet is as follows: public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { logger.debug(String.format("Intercepted a request for an item in the custom directory [%s]",request.getRequestURL().toString())); String requestUri = request.getRequestURI(); // Check that the file name contains a text string if (requestUri.toLowerCase(Locale.UK).contains("someText")){ logger.debug(String.format("We are interested in this file [%s]",requestUri)); File file = new File(requestUri); boolean fileExists = file.exists(); logger.debug(String.format("Checking to see if file [%s] exists [%s].",requestUri,fileExists)); // if the file exists just forward it to the file if (fileExists){ getServletConfig().getServletContext().getRequestDispatcher( requestUri).forward(request,response); } else { // Otherwise redirect to default.jsp getServletConfig().getServletContext().getRequestDispatcher( "/custom/default.jsp").forward(request,response); } } else { // We aren't responsible for checking this file exists just pass it on to the requeseted jsp getServletConfig().getServletContext().getRequestDispatcher( requestUri).forward(request,response); } } This seems to result in an error 500 from tomcat, I think this is because the servlet is redirecting to the same folder which is then being intercepted again by the servlet, resulting in an infinite loop. Is there a better way to do this? I'm lead to believe that I could use filters to do this, but I don't know very much about them.

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  • Hibernate one-to-one mapping

    - by Andrey Yaskulsky
    I have one-to-one hibernate mapping between class Student and class Points: @Entity @Table(name = "Users") public class Student implements IUser { @Id @Column(name = "id") private int id; @Column(name = "name") private String name; @Column(name = "password") private String password; @OneToOne(fetch = FetchType.EAGER, mappedBy = "student") private Points points; @Column(name = "type") private int type = getType(); //gets and sets... @Entity @Table(name = "Points") public class Points { @GenericGenerator(name = "generator", strategy = "foreign", parameters = @Parameter(name = "property", value = "student")) @Id @GeneratedValue(generator = "generator") @Column(name = "id", unique = true, nullable = false) private int Id; @OneToOne @PrimaryKeyJoinColumn private Student student; //gets and sets And then i do: Student student = new Student(); student.setId(1); student.setName("Andrew"); student.setPassword("Password"); Points points = new Points(); points.setPoints(0.99); student.setPoints(points); points.setStudent(student); Session session = HibernateUtil.getSessionFactory().getCurrentSession(); session.beginTransaction(); session.save(student); session.getTransaction().commit(); And hibernate saves student in the table but not saves corresponding points. Is it OK? Should i save points separately?

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  • SLF4J, Common Logging, console output

    - by Mauricio Scheffer
    I have this 3rd party library that has: slf4j-api-1.5.5.jar slf4j-jdk14-1.5.5.jar jcl-over-slf4j-1.5.5.jar I want to write some tests against this library and see its log output, and I don't want to add any more logging libraries (no log4j or anything else). I understand that SLF4J and Common Logging are both logging abstractions so I probably need to write my own simple concrete logger (or maybe not, since jcl-over-slf4j includes org.apache.commons.logging.impl.SimpleLog?). If so, what interfaces should I implement, and more importantly, how do I set up SL4J/Common Logging to use my logger in my test? I read in the SLF4J docs that I have to modify the StaticLoggerBinder class... does that really mean that I actually have to download SLF4J sources, modify the class and recompile it?

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  • alternatedocroot

    - by ring bearer
    Using Sun Glassfish Enterprise server v2.1.1 I am using "alternatedocroot" via sun-web.xml for my web application to abstract out static content from actual deploy-able code (EAR/WAR) What I have is a cluster of two server instances distributed across two physical hosts - HOST1 and HOST2. "alternatedocroot" points to /data/static-content/ on both HOST1 and HOST2. Would DAS (Domain application server )take care of syncing /data/static-content between HOST1 and HOST2 if I use syncinstances=true option while starting up the cluster? Thanks!

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