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  • Mysql maven jpa skeleton

    - by coubeatczech
    Hi, is there a skeleton for a project using mysql, some eclipse/top link with RESOURCE_LOCAL as connection type? Preferably using maven. I'm searching for it for hours and can't get running even the sipmlest exaple. So if you had it ready and running, please, post :-). Even something as simple as these two classes only. @Entity public class Message implements Serializable{ public Message() {} public Message(String s){ this.s = s; } @Id String s; public String getS(){ return s; } } public class App { static private EntityManagerFactory emf; static private EntityManager em; public static void main( String[] args ) { emf = Persistence.createEntityManagerFactory("persistence"); em = emf.createEntityManager(); Message m = new Message("abc"); em.persist(m); } }

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  • BufferedImage.getGraphics() resulting in memory leak, is there a fix?

    - by user359202
    Hi friends, I'm having problem with some framework API calling BufferedImage.getGraphics() method and thus causing memory leak. What this method does is that it always calls BufferedImage.createGraphics(). On a windows machine, createGraphics() is handled by Win32GraphicsEnvironment which keeps a listeners list inside its field displayChanger. When I call getGraphics on my BufferedImage someChart, someChart's SurfaceManager(which retains a reference to someChart) is added to the listeners map in Win32GraphicsEnvironment, preventing someChart to be garbage collected. Nothing afterwards removes someChart's SurfaceManager from the listeners map. In general, the summarized path stopping a BufferedImage from being garbage collected, once getGraphics is called, is as follows: GC Root - localGraphicsEnvironment(Win32GraphicsEnvironment) - displayChanger(SunDisplayChanger) - listeners(Map) - key(D3DChachingSurfaceManager) - bImg(BufferedImage) I could have changed the framework's code so that after every called to BufferedImage.getGraphics(), I keep a reference to the BufferedImage's SurfaceManager. Then, I get hold of localGraphicsEnvironment, cast it to Win32GraphicsEnvironment, then call removeDisplayChangedListener() using the reference to the BufferedImage's SurfaceManager. But I don't think this is a proper way to solve the problem. Could someone please help me with this issue? Thanks a lot!

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  • How often should we write unit tests?

    - by Midnight Blue
    Hi, I am recently introduced to the test-driven approach to development by my mentor at work, and he encourages me to write an unit-test whenenver "it makes sense." I understand some benefits of having a throughout unit-test suite for both regression testing and refractoring, but I do wonder how often and how throughout we should write unit-test. My mentor/development lead asks me to write a new unit test-case for a newly written control flow in a method that is already being tested by the exsisting test class, and I think it is an overkill. How often do you write your unit tests, and how detailed do you think your unit tests should be? Thanks!

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  • Common Utility for Exception Searching

    - by Andrew
    I wrote this little helper method to search the exception chain for a particular exception (either equals or super class). However, this seems like a solution to a common problem, so was thinking it must already exist somewhere, possibly in a library I have already imported. So, any ideas on if/where this might exist? boolean exceptionSearch(Exception base, Class<?> search) { Throwable e = base; do { if (search.isAssignableFrom(e.getClass())) { return true; } } while ((e = e.getCause()) != null); return false; }

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  • How to efficiently implement a strategy pattern with spring ?

    - by Anth0
    I have a web application developped in J2EE 1.5 with Spring framework. Application contains "dashboards" which are simple pages where a bunch of information are regrouped and where user can modify some status. Managers want me to add a logging system in database for three of theses dashboards. Each dashboard has different information but the log should be traced by date and user's login. What I'd like to do is to implement the Strategy pattern kind of like this : interface DashboardLog { void createLog(String login, Date now); } // Implementation for one dashboard class PrintDashboardLog implements DashboardLog { Integer docId; String status; void createLog(String login, Date now){ // Some code } } class DashboardsManager { DashboardLog logger; String login; Date now; void createLog(){ logger.log(login,now); } } class UpdateDocAction{ DashboardsManager dbManager; void updateSomeField(){ // Some action // Now it's time to log dbManagers.setLogger = new PrintDashboardLog(docId, status); dbManagers.createLog(); } } Is it "correct" (good practice, performance, ...) to do it this way ? Is there a better way ? Note :I did not write basic stuff like constructors and getter/setter.

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  • How to export EclipseLink objects to XML

    - by Raven
    Hi, is there an easy approach to store my model, which I use with EclipseLink, in XML files? I want to implement an export functionality in my program and I was wondering if this can be done with eclipselink or with any other framework. Thanks

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  • Why is BigDecimal.equals specified to compare both value and scale individually?

    - by bacar
    This is not a question about how to compare two BigDecimal objects - I know that you can use compareTo instead of equals to do that, since equals is documented as: Unlike compareTo, this method considers two BigDecimal objects equal only if they are equal in value and scale (thus 2.0 is not equal to 2.00 when compared by this method). The question is: why has the equals been specified in this seemingly counter-intuitive manner? That is, why is it important to be able to distinguish between 2.0 and 2.00? It seems likely that there must be a reason for this, since the Comparable documentation, which specifies the compareTo method, states: It is strongly recommended (though not required) that natural orderings be consistent with equals I imagine there must be a good reason for ignoring this recommendation.

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  • ImageIcon loads no image

    - by neville
    I'm trying to get image built from tiled set of images So to JPanel I'm adding JButtons with ImageIcons. All images are in folder with my classes (NetBeans), and they're named u1, u2, ..., u16. But on button there is no image shown. What am I doing wrong ? JPanel panel = new JPanel(new GridLayout(4, 4, 3, 3)); for (int i = 1; i < 17; i++) { JLabel l = new JLabel(new ImageIcon("u"+i+".jpg"), JLabel.CENTER); l.setBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED)); panel.add(l); }

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  • What can you do in the ant Task.init() method?

    - by skiphoppy
    I'm developing a few custom ant tasks that all need to initialize the same objects. I wanted to initialize those object's in a common superclass that extends from Task, in the init() method. But I see from the lifecycle of an ant task that init() gets called before the tasks child elements and attributes are set. So all of the data I need for initializing those objects is unavailable during init(), if I am reading right. So, why is init() called at this point? What do you even know that you could use in init()? What could it be used for? (And is there some other method that I can rely on to be called before execute(), but after my data is available?)

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  • LinkedList.contains execution speed

    - by Le_Coeur
    Why Methode LinkedList.contains() runs quickly than such implementation: for (String s : list) if (s.equals(element)) return true; return false; I don't see great difference between this to implementations(i consider that search objects aren't nulls), same iterator and equals operation

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  • Possible loss of precision / [type] cannot be dereferenced

    - by Samuel
    I have been looking around a lot but i simply can't find a nice solution to this... Point mouse = MouseInfo.getPointerInfo().getLocation(); int dx = (BULLET_SPEED*Math.abs(x - mouse.getX()))/ (Math.abs(y - mouse.getY()) + Math.abs(x - mouse.getX()))* (x - mouse.getX())/Math.abs(x - mouse.getX()); In this constellation i get: Possible loss of precision, when i change e.g (x - mouse.getX()) to (x - mouse.getX()).doubleValue() it says double cannot be dereferenced, when i add intValue() somewhere it says int cannot be dereferenced. What's my mistake? [x, y are integers | BULLET_SPEED is a static final int] Thanks!

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  • Can you use regular expressions in struts-config.xml?

    - by rquinn
    I'm trying to route these two url's to different Actions. We are using Struts 1.2: /abc-def/products /abc-def I tried putting this action first: <action path="/abc*/products" type="com.business.exampleAction"> <forward name="success" path="/go"/> </action> and then this one after: <action path="/abc*" type="com.business.differentExampleAction"> <forward name="success" path="/goElsewhere"/> </action> but it always goes to the second action (differentExampleAction in this case). I've tried various iterations for the , like . or (.*), but haven't found anything that actually works yet. From what I've read, it seems like the only regular-expression-like characters allowed in struts-config are the wildcard symbols (* and **), but I hope I am wrong.

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  • Solr; What does this mean?

    - by Camran
    At the end of the README.txt file which is located in the example directory under solr, I find this line: NOTE: This Solr example server references SolrCell jars outside of the server directory with statements in the solrconfig.xml. If you make a copy of this example server and wish to use the ExtractingRequestHandler (SolrCell), you will need to copy the required jars into solr/lib or update the paths to the jars in your solrconfig.xml What does this mean? Do I have to make some adjustment before uploading solr to my server? Also, if you know, what is Solr-nightly:s difference to regular solr? The tutorial states "solr-nightly.zip" but on their download section I cant find it.

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  • Buffering db inserts in multithreaded program

    - by Winter
    I have a system which breaks a large taks into small tasks using about 30 threads as a time. As each individual thread finishes it persists its calculated results to the database. What I want to achieve is to have each thread pass its results to a new persisance class that will perform a type of double buffering and data persistance while running in its own thread. For example, after 100 threads have moved their data to the buffer the persistance class then the persistance class swaps the buffers and persists all 100 entries to the database. This would allow utilization of prepared statements and thus cut way down on the I/O between the program and the database. Is there a pattern or good example of this type of multithreading double buffering?

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  • Prevent browser form submission when Wicket AjaxFormValidatingBehaviour validation fails

    - by Brian Laframboise
    I have a Page with a Wizard component. The user can navigate the panels of the wizard by using the next and previous buttons which I have performing full (non-ajax) form submissions so that the app is back-button friendly. When the next button is clicked, I would like to attempt ajax form validation (if javascript is enabled). I tried doing: nextButton.add( new AjaxFormValidatingBehavior( form, "onsubmit") ); to add such validation. The behaviour works - however, when validation errors occur the browser still submits the entire form. What is the Wicket way to prevent the browser from submitting the form in this case?

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  • runtime/compile time polymorphism

    - by dmadhavaraj
    Hi , In the below code , why b1.subtract() fails . Please explain me the reason ie., what happens in JVM while invoking that method . class Base { public void add() { System.out.println("Base ADD"); } } class Child extends Base { public void add(){ System.out.println("Child ADD"); } public void subtract() { System.out.println("Child Subtract"); } } class MainClass { public static void main(String args[]) { Base b1 = new Base(); Base b2 = new Child(); Child b3 = new Child(); b1.add(); b1.subtract(); // ?????????** b2.add(); b3.subtract(); } }

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  • Why wait should always be in synchronized block

    - by diy
    Hi gents, We all know that in order to invoke Object.wait() , this call must be placed in synchronized block,otherwise,IllegalMonitorStateException is thrown.But what's the reason for making this restriction?I know that wait() releases the monitor, but why do we need to explicitly acquire the monitor by making particular block synchronized and then release the monitor by calling wait() ? What is the potential damage if it was possible to invoke wait() outside synch block, retaining it's semantics - suspending the caller thread ? Thanks in advance

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  • DefaultStyledDocument.styleChanged(Style style) may not run in a timely manner?

    - by Paul Reiners
    I'm experiencing an intermittent problem with a class that extends javax.swing.text.DefaultStyledDocument. This document is being sent to a printer. Most of the time the formatting of the document looks correct, but once in a while it doesn't. It looks like some of the changes in the formatting have not been applied. I took a look at the DefaultStyledDocument.styleChanged(Style style) code: /** * Called when any of this document's styles have changed. * Subclasses may wish to be intelligent about what gets damaged. * * @param style The Style that has changed. */ protected void styleChanged(Style style) { // Only propagate change updated if have content if (getLength() != 0) { // lazily create a ChangeUpdateRunnable if (updateRunnable == null) { updateRunnable = new ChangeUpdateRunnable(); } // We may get a whole batch of these at once, so only // queue the runnable if it is not already pending synchronized(updateRunnable) { if (!updateRunnable.isPending) { SwingUtilities.invokeLater(updateRunnable); updateRunnable.isPending = true; } } } } /** * When run this creates a change event for the complete document * and fires it. */ class ChangeUpdateRunnable implements Runnable { boolean isPending = false; public void run() { synchronized(this) { isPending = false; } try { writeLock(); DefaultDocumentEvent dde = new DefaultDocumentEvent(0, getLength(), DocumentEvent.EventType.CHANGE); dde.end(); fireChangedUpdate(dde); } finally { writeUnlock(); } } } Does the fact that SwingUtilities.invokeLater(updateRunnable) is called, rather than invokeAndWait(updateRunnable), mean that I can't count on my formatting changes appearing in the document before it is rendered? If that is the case, is there a way to ensure that I don't proceed with rendering until the updates have occurred?

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  • Changing the icon of a .JAR file

    - by Demonick
    How can I change the icon of a .JAR file I want to distribute? I have changed the icon that shows when the program is run, but I want to change the icon in the environment (e.g. Windows XP), that is for the file itself. I googled, but the best I could find is converting the .JAR to a .EXE, which is not the best choice.

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