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  • How to fire off a asych thread in a web application, and gaurantee only 1 thread fires?

    - by Blankman
    I want to cache a object in memory. Regenerating the object when the cache expires is fairly expensive, so I want to do the following: When the cache is "about" to expire, I want to fire off a asychronous thread that will go and rebuild the object and then reset the cache. One thing I am worry about is multiple threads firing to fetch the object to cache, I only want a single thread doing this, realizing many people will be hitting the website. This might not be the best use case to do this, but I want to know how to do this sort of thing.

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  • Writing a line in a JTextArea from another class

    - by Christopher Nastovski
    I'm trying to use a Method in my class 'Visual' to write a line of code into a JTextArea and it prints when I call it from 'Visual' but when I call it from 'Login' It only prints Text into the Console, not to the TextArea. private static Visual Visual; Visual.WriteLine("I'm sorry, your username or password is incorrect. Please try again."); or private static Visual Visual = new Visual(); Visual.WriteLine("I'm sorry, your username or password is incorrect. Please try again."); Dont work form 'Login' But, WriteLine("Test"); works from 'Visual', the class that the method is in. Here's the method in 'Visual' public void WriteLine(String Text) { System.out.println(Text); SystemFeed.append(Text.toString() + "\n"); SystemFeed.setCaretPosition(SystemFeed.getDocument().getLength()); }

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  • How To Configure Query Cacheing in EclipseLink

    - by rustyshelf
    I have a collection of states, that I want to cache for the life of the application, preferably after it is called for the first time. I'm using EclipseLink as my persistence provider. In my EJB3 entity I have the following code: @Cache @NamedQueries({ @NamedQuery( name = "State.findAll", query = "SELECT s FROM State s", hints = { @QueryHint(name=QueryHints.CACHE_USAGE, value=CacheUsage.CheckCacheThenDatabase), @QueryHint(name=QueryHints.READ_ONLY, value=HintValues.TRUE) } ) }) This doesn't seem to do anything though, if I monitor the SQL queries going to MySQL it still does a select each time my Session Bean uses this NamedQuery. What is the correct way to configure this query so that it is only ever read once from the database, preferably across all sessions? Edit: I am calling the query like this: Query query = em.createNamedQuery("State.findAll"); List<State> states = query.getResultList();

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  • Design pattern: polymorphisim for list of objects

    - by ziang
    Suppose I have a class A, and A1, A2 inherits from A. There are 2 functions: List<A1> getListA1(){...} List<A2> getListA2(){...} Now I want to do something similar to both A1 and A2 in another function public void process(List<A>){...} If I want to pass the instance of either ListA1 or ListA2, of course the types doesn't match because the compiler doesn't allow the coercion from List< A1 to List< A. I can't do something like this: List<A1> listA1 = getListA1(); List<A> newList = (List<A>)listA1; //this is not allowed. So what is the best approach to the process()? Is there any way to do it in a universal way rather than write the similar code to both List and List?

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  • Use the serialVersionUID or suppress warnings?

    - by Okami
    Dear all, first thing to note is the serialVersionUID of a class implementing Interface Serializable is not in question. What if we create a class that for example extends HttpServlet? It also should have a serialVersionUID. If someone knows that this object will never be serialized should he define it or add an annotation to suppress those warnings? What would you do and why? Thanks for sharing your thoughts. Okami

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  • ExceptionHandling with Spring 3

    - by mjf
    I have this controller: @RequestMapping(value = "*.xls", method = RequestMethod.GET) public String excel(Model model) { return "excel"; The excel wiew opens actually a ExcelViewer, which is build in method protected void buildExcelDocument(Map<String, Object> map, WritableWorkbook ww, HttpServletRequest hsr, HttpServletResponse hsr1) throws Exception { Class.writecontent Class.writeMoreContent Called methods write content to the Excel sheet and they can throw e.g biffException. How can I show a certain error page when Exception is occured? I tried this @Controller public class ExcelController { @ExceptionHandler(BiffException.class) public String handleException(BiffException ex) { return "fail"; } @RequestMapping(value = "*.xls", method = RequestMethod.GET) public String excel(Model model) { return "excel"; } } But I'm getting the server's error message about Exceptions. Maybe a bean definition missing?

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  • JButtons re-enable themselves after being disabled

    - by Anarchist
    I have an array of JButtons which form a keypad interface. After six numbers are entered I want to disable the keypad so that no further numbers can be entered by the user. I have written the code and the buttons do disable until the mouse hovers above any of them, then the buttons seem to re-enable themselves and run actionEvents added to them. The full code is available here. Possible things that I think are wrong. There is some sort of MouseListener which is ignoring when I set button.setEnabled(false); I haven't separated attributes from the buildGUI(); correctly, I only did this anyway so that the inner class could access them. Possibly something to do with the gridLayout as disabling the buttons seems to work for my services JPanel buttons.

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  • Oval collision detection not working properly

    - by William
    So I'm trying to implement a test where a oval can connect with a circle, but it's not working. edist = (float) Math.sqrt(Math.pow((px + ((pwidth/2) )) - (bx + (bsize/2)), 2) + Math.pow(-((py + ((pwidth/2)) ) - (bx + (bsize/2))), 2)); and here is the full code (requires Slick2D): import org.newdawn.slick.AppGameContainer; import org.newdawn.slick.BasicGame; import org.newdawn.slick.Color; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.Input; import org.newdawn.slick.SlickException; public class ColTest extends BasicGame{ float px = 50; float py = 50; float pheight = 50; float pwidth = 50; float bx = 200; float by = 200; float bsize = 200; float edist; float pspeed = 3; Input input; public ColTest() { super("ColTest"); } @Override public void init(GameContainer gc) throws SlickException { } @Override public void update(GameContainer gc, int delta) throws SlickException { input = gc.getInput(); try{ if(input.isKeyDown(Input.KEY_UP)) py-=pspeed; if(input.isKeyDown(Input.KEY_DOWN)) py+=pspeed; if(input.isKeyDown(Input.KEY_LEFT)) px-=pspeed; if(input.isKeyDown(Input.KEY_RIGHT)) px+=pspeed; } catch(Exception e){} } public void render(GameContainer gc, Graphics g) throws SlickException { g.setColor(new Color(255,255,255)); g.drawString("col: " + col(), 10, 10); g.drawString("edist: " + edist + " dist: " + dist, 10, 100); g.fillRect(px, py, pwidth, pheight); g.setColor(new Color(255,0,255)); g.fillOval(px, py, pwidth, pheight); g.setColor(new Color(255,255,255)); g.fillOval(200, 200, 200, 200); } public boolean col(){ edist = (float) Math.sqrt(Math.pow((px + ((pwidth/2) )) - (bx + (bsize/2)), 2) + Math.pow(-((py + ((pwidth/2)) ) - (bx + (bsize/2))), 2)); if(edist <= (bsize/2) + (px + (pwidth/2))) return true; else return false; } public float rotate(float x, float y, float ox, float oy, float a, boolean b) { float dst = (float) Math.sqrt(Math.pow(x-ox,2.0)+ Math.pow(y-oy,2.0)); float oa = (float) Math.atan2(y-oy,x-ox); if(b) return (float) Math.cos(oa + Math.toRadians(a))*dst+ox; else return (float) Math.sin(oa + Math.toRadians(a))*dst+oy; } public static void main(String[] args) throws SlickException { AppGameContainer app = new AppGameContainer( new ColTest() ); app.setShowFPS(false); app.setAlwaysRender(true); app.setTargetFrameRate(60); app.setDisplayMode(800, 600, false); app.start(); } }

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  • Semantics of repeated acknowledgments in JMS

    - by Lajos Nagy
    Suppose I decide to call acknowledgment() on a JMS message several times. Say the first call fails (for non-permanent reason). Does the success of the second (or any subsequent) call guarantee that the message is now acknowledged? Is the exact behavior of acknowledgement() specified anywhere?

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  • Binding of JText fields value to Info Class

    - by Faizan Ahmed
    Is there any way to automatic binding of Swing JTextFields to Info Class. e.g private JTextField receiptId; private JTextField Id; public class Info { private string receiptId; private String id; // Getters and Setters } Is there any way when I entered values from Swing page then automatically values bind with my Info class? After that I can pass my Info object to other classes instead of sending all Text Fields.

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  • Spring @Value annotation not using defaults when property is not present

    - by garyj
    Hi All I am trying to use @Value annotation in the parameters of a constructor as follows: @Autowired public StringEncryptor( @Value("${encryptor.password:\"\"}") String password, @Value("${encryptor.algorithm:\"PBEWithMD5AndTripleDES\"}") String algorithm, @Value("${encryptor.poolSize:10}") Integer poolSize, @Value("${encryptor.salt:\"\"}") String salt) { ... } When the properties file is present on the classpath, the properties are loaded perfectly and the test executes fine. However when I remove the properties file from the classpath, I would have expected that the default values would have been used, for example poolSize would be set to 10 or algorithm to PBEWithMD5AndTripleDES however this is not the case. Running the code through a debugger (which would only work after changing @Value("${encryptor.poolSize:10}") Integer poolSize to @Value("${encryptor.poolSize:10}") String poolSize as it was causing NumberFormatExceptions) I find that the defaults are not being set and the parameters are in the form of: poolSize = ${encryptor.poolSize:10} or algorithm = ${encryptor.algorithm:"PBEWithMD5AndTripleDES"} rather than the expected poolSize = 10 or algorithm = "PBEWithMD5AndTripleDES" Based on SPR-4785 the notation such as ${my.property:myDefaultValue} should work. Yet it's not happening for me! Thank you

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  • How to put PrintWriter object content in to table cell

    - by user3599482
    I have a small problem about a content returning from servlet to put in table cell. In javascript I am calling servlet method using post, it returns some content and I have to put it in two different <td> cells. here is my code, In javascript, $.post('<%=request.getContextPath()%>/controller/UserLockController',{'userName':userName,'status':status}, function(data) { document.getElementById("status_"+userName).innerHTML=data; document.getElementById("td_"+userName).innerHTML=data; }); in servlet it writes as, out.println("<td id=\"status_"+inputParam+"\">Locked</td>"); out.println("<td id=\"td_"+inputParam+"\"><a href=\"#\" class=\"btn btn-sm btn-primary unlockBtn\" id=\"togBtn_"+inputParam+"\" onClick=\"LockAccount('"+inputParam+"','"+status+"')\">UnLock</td>"); Here content is returning but problem is the both <td> return from servlet will fit in single cell of html table. how to solve this please help me.

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  • JMS Acknowledge Asynchronous Message

    - by x1a0
    Hi, How do I acknowledge a message when I am using a message listener? I get the following error when I try to do an acknowledge in my message listener. A synchronous method call is not permitted when a session is being used asynchronously: 'acknowledge'

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  • How do I find resources in a .jar on the classpath?

    - by Brabster
    If I have a collection of resource files in a directory on my classpath, I can enumerate them using ClassLoader.getResources(location). For example if I have /mydir/myresource.properties on the classpath, I can call the classloader's getResources("mydir") and get an enumeration of URLs containing myresource.properties. When I pack up the exact same resources into a .jar, I don't get anything in the enumeration of URLs when I make the call. I've only replaced the folder structure with a jar containing those folders (it's a webapp, so the jar is going into /WEB-INF/lib). I've also got a number of other calls using getResourceAsStream(location) to get other resources individually by name and they're all working fine. What's different about enumerating resources when the resources are in a .jar?

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  • any way to use ajax with jstl customtags without duplicating tags in javascript?

    - by CodeMonkeyB
    I am working on a page where part of the content is loaded normally and the pages are rendered using jsps. The product images and links generated on that page are by custom jstl tags. When the user scrolls more products are requested from the server in a JSON response and then using UnderscoreJS templates they are rendered and added to the bottom of the page. Is there any way I can use the JSTL tags in Javascript without recreating them using a javascript function (it won't be possible to re-create all of them in javascript). What is the best way to handle this scenario? I guess I could return a rendered html response for the ajax call, but that would mean I have some ajax requests which use json and some that use rendered html...

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  • Jaxb to generate the XML directly to the OutputStream

    - by sonu
    Hi, I have a 500Mb csv file. I need to convert it into XML file. I am using the Jaxb to created the xml file. It is working fine for small amout of data. but for large amout of data like 300 mb it is throwing out of memory exception. Can anyone tell me that How can I create each element and write it into a file without creating the whole tree using the jaxb?" Thanks Sonu

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  • What is the fastest findByName query with hibernate?

    - by Karussell
    I am sure I can improve the performance of the following findByName query of hibernate: public List<User> findByName(String name) { session.createCriteria(User.class).add(Restrictions.eq("name", name)).list(); } In which way should I improve it or even more important: in which ways should I improve it first? I will need the full object with all the collections (layz or not) and deps of this class.

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  • How to use Scanner to accept only valid int as input

    - by John
    I'm trying to make a small program more robust and I need some help with that. Scanner kb = new Scanner(System.in); int num1; int num2 = 0; System.out.print("Enter number 1: "); num1 = kb.nextInt(); while(num2<num1) { System.out.print("Enter number 2: "); num2 = kb.nextInt(); } Number 2 has to be greater than number 1 Also I want the program to automatically check and ignore if the user enters a character instead of a number. Because right now when a user enters for example r instead of a number the program just exits.

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