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  • Whats a good API for generating reports for a java web application?

    - by Ahmad
    I have a J2EE application that has a lot of reports, the situation now is the following: Report filters' values are sent to the application over DWR mainly, the data are retrieved from Oracle DB throw DB procedures and returned back to the client. However, some customization is required every now and then (new data filters, columns, ordering, ...), and these changes are painful to implement since we need to modify the JSPs, DB Procedures, the application itself, ... What API do you recommend to use for such reports?

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  • java methods and race condition in a jsp/servlets application.

    - by A.S al-shammari
    Hi. Suppose that I have a method called doSomething() and I want to use this method in a multithreaded application (each servlet inherits from HttpServlet).I'm wondering if it is possible that a race condition will occur in the following cases: doSomething() is not staic method and it writes values to a database. doSomething() is static method but it does not write values to a database. what I have noticed that many methods in my application may lead to a race condition or dirty read/write. for example , I have a Poll System , and for each voting operation, a certain method will change a single cell value for that poll as the following: [poll_id | poll_data ] [1 | {choice_1 : 10, choice_2 : 20}] will the JSP/Servlets app solve these issues by itself, or I have to solve all that by myself? Thanks..

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  • Java JAX-WS web-service client: how log request & response xml ?

    - by EugeneP
    I created an implementation of LoggingHandler that implements SOAPHandler It should log whenever handleMessage triggers. [ And it is never called in my case ] then : MyService service = new MyService(); MyServicePort port = service.getPortType(); now I try this: BindingProvider bindingProvider = (BindingProvider)port; bindingProvider.getBinding().getHandlerChain().add(new LoggingHandler()); I do not see any request / response xml though. Can you suggest any solution? Maybe there's other way to see output and request xml s ?

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  • Need help with strange Class#getResource() issue

    - by Andreas_D
    I have some legacy code that reads a configuration file from an existing jar, like: URL url = SomeClass.class.getResource("/configuration.properties"); // some more code here using url variable InputStream in = url.openStream(); Obviously it worked before but when I execute this code, the URL is valid but I get an IOException on the third line, saying it can't find the file. The url is something like "file:jar:c:/path/to/jar/somejar.jar!configuration.properties" so it doesn't look like a classpath issue - java knows pretty well where the file can be found.. The above code is part of an ant task and it fails while the task is executed. Strange enough - I copied the code and the jar file into a separate class and it works as expected, the properties file is readable. At some point I changed the code of the ant task to URL url = SomeClass.class.getResource("/configuration.properties"); // some more code here using url variable InputStream in = SomeClass.class.getResourceAsStream("/configuration.properties"); and now it works - just until it crashes in another class where a similiar access pattern is implemented.. Why could it have worked before, why does it fail now? The only difference I see at the moment is, that the old build was done with java 1.4 while I'm trying it with Java 6 now. Workaround Today I installed Java 1.4.2_19 on the build server and made ant to use it. To my totally frustrating surprise: The problem is gone. It looks to me, that java 1.4.2 can handle URLs of this type while Java 1.6 can't (at least in my context/environment). I'm still hoping for an explanation although I'm facing the work to rewrite parts of the code to use Class#getRessourceAsStream which behaved much more stable...

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  • How do you draw a string centered vertically in Java?

    - by Paul Alexander
    I know it's a simple concept but I'm struggling with the font metrics. Centering horizontally isn't too hard but vertically seems a bit difficult. I've tried using the FontMetrics getAscent, getLeading, getXXXX methods in various combinations but no matter what I've tried the text is always off by a few pixels. Is there a way to measure the exact height of the text so that it is exactly centered.

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  • Getting a cryptic error on my simple Java program, comparing char[i] to a string.

    - by Sergio Tapia
    public static void ejemplosString(String palabra){ char[] letras = palabra.toCharArray(); int contadorVocales = 0; for (int i = 0; i < letras.length; i++) { if (char[i] == 'a') { contadorVocales++; } if (char[i] == "e") { contadorVocales++; } if (char[i] == "i") { contadorVocales++; } if (char[i] == "o") { contadorVocales++; } if (char[i] == "u") { contadorVocales++; } } } Getting the error on every If statement. Any guidance?

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  • How do you raise a Java BigInteger to the power of a BigInteger without doing modular arithmetic?

    - by angstrom91
    I'm doing some large integer computing, and I need to raise a BigInteger to the power of another BigInteger. The .pow() method does what I want, but takes an int value as an argument. The .modPow method takes a BigInteger as an argument, but I do not want an answer congruent to the value I'm trying to compute. My BigInteger exponent is too large to be represented as an int, can someone suggest a way to work around this limitation?

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  • Is it bad to explicitly compare against boolean constants e.g. if (b == false) in Java?

    - by polygenelubricants
    Is it bad to write: if (b == false) //... while (b != true) //... Is it always better to instead write: if (!b) //... while (!b) //... Presumably there is no difference in performance (or is there?), but how do you weigh the explicitness, the conciseness, the clarity, the readability, etc between the two? Note: the variable name b is just used as an example, ala foo and bar.

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  • How to preview any files inside a Java application ?

    - by Studer
    I'm using a JTree to browse the content of a folder and I want that when a user click on a file, the software shows a preview of it (a screenshot of its first page). The files are mostly Office documents and PDF. I manage to do it for PDF file using a module downloaded from Sun, but I'd like to know if there is a way to do it using any software (JARs preferably) or even the built-in Windows API. I was thinking of converting the file to PDF then do a preview of this PDF but this isn't optimal. Any ideas ?

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  • Java - How to declare table[i][j] elements as instance variables?

    - by JDelage
    All, I am trying to code a Connect4 game. For this, I have created a P4Game class and a P4Board class which represents the i X j dimensions of the Connect4 board. In P4Game, I have the following: public class P4Game{ //INSTANCE VARIABLES private int nbLines; private int nbColumns; private P4Board [][] position; //CONSTRUCTOR public P4Game(int nbLines, int nbColumns){ this.nbColumns = nbColumns; this.nbLines = nbLines; P4Board [][] position = new P4Board [nbLines][nbColumns]; //Creates the table to receive the instances of the P4Board object.*/ for (int i=0; i<nbLines; i++){ for (int j=0; j<nbColumns; j++){ this.position[i][j] = new P4Board(i,j); //Meant to create each object at (line=i, column=j) } } } This causes a NullPointerException in the nested loops where I mention this.position[i][j]. I reference those objects in other methods of this class so I need them to be instance variables. I suppose the exception is due to the fact that I have not listed the table element position[i][j] as an instance variable at the beginning of the class. my question to people here is (1) is my assumption correct, and if so (2) what would be the syntax to declare instance variables of this form? Thank you all for your help with what I realize is a very basic question. Hopefully it will also benefit other newbies. Cheers, JDelage

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  • How to read comma separated values from text file in JAVA?

    - by user1425223
    I have got this text file with latitude and longitude values of different points on a map. I want to store these coordinates into a mySQL database using hibernate. I want to know how can I split my string into latitudes and longitudes? What is the general way to do these type of things that is with other delimiters like space, tab etc.? File: 28.515046280572285,77.38258838653564 28.51430151808072,77.38336086273193 28.513566177802456,77.38413333892822 28.512830832397192,77.38490581512451 28.51208605426073,77.3856782913208 28.511341270865113,77.38645076751709 28.510530488025346,77.38720178604126 28.509615992924807,77.38790988922119 28.50875805732363,77.38862872123718 28.507994394490268,77.38943338394165 28.50728729434496,77.39038825035095 28.506674470385246,77.39145040512085 28.506174780521828,77.39260911941528 28.505665660113582,77.39376783370972 28.505156537248446,77.39492654800415 28.50466626846366,77.39608526229858 28.504175997400655,77.39724397659302 28.503685724059455,77.39840269088745 28.503195448440064,77.39956140518188 28.50276174118543,77.4007523059845 28.502309175192945,77.40194320678711 28.50185660725938,77.40313410758972 28.50140403738471,77.40432500839233 28.500951465568985,77.40551590919495 28.500498891812207,77.40670680999756 28.5000463161144,77.40789771080017 28.49959373847559,77.40908861160278 Code I am using to read from file: try { BufferedReader in = new BufferedReader(new FileReader("G:\\RoutePPAdvant2.txt")); String str; str = in.readLine(); while ((str = in.readLine()) != null) { System.out.println(str); } in.close(); } catch (IOException e) { System.out.println("File Read Error"); }

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  • Java: How to test methods that call System.exit()?

    - by Chris Conway
    I've got a few methods that should call System.exit() on certain inputs. Unfortunately, testing these cases causes JUnit to terminate! Putting the method calls in a new Thread doesn't seem to help, since System.exit() terminates the JVM, not just the current thread. Are there any common patterns for dealing with this? For example, can I subsitute a stub for System.exit()? [EDIT] The class in question is actually a command-line tool which I'm attempting to test inside JUnit. Maybe JUnit is simply not the right tool for the job? Suggestions for complementary regression testing tools are welcome (preferably something that integrates well with JUnit and EclEmma).

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  • Java Swing: how to listen to JComboBox's width changes?

    - by agnieszka
    I tried PropertyChangeListener with property set to "width", "Width", "size" and "Size". PropertyChangeListener widthChangeListener = new PropertyChangeListener() { @Override public void propertyChange(PropertyChangeEvent evt) { //code } }; streamsComboBox.addPropertyChangeListener("width", widthChangeListener); projectsComboBox.addPropertyChangeListener("width", widthChangeListener); vobsComboBox.addPropertyChangeListener("width", widthChangeListener); Nothing works - the handler method is never fired. What should I do to handle JComboBox's size change? Where does the property name come from anyway?

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  • When does the call() method get called in a Java Executor using Callable objects?

    - by MalcomTucker
    This is some sample code from an example. What I need to know is when call() gets called on the callable? What triggers it? public class CallableExample { public static class WordLengthCallable implements Callable { private String word; public WordLengthCallable(String word) { this.word = word; } public Integer call() { return Integer.valueOf(word.length()); } } public static void main(String args[]) throws Exception { ExecutorService pool = Executors.newFixedThreadPool(3); Set<Future<Integer>> set = new HashSet<Future<Integer>>(); for (String word: args) { Callable<Integer> callable = new WordLengthCallable(word); Future<Integer> future = pool.submit(callable); //**DOES THIS CALL call()?** set.add(future); } int sum = 0; for (Future<Integer> future : set) { sum += future.get();//**OR DOES THIS CALL call()?** } System.out.printf("The sum of lengths is %s%n", sum); System.exit(sum); } }

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  • JAVA: 500 Worker Threads, what kind of thread pool?

    - by Submerged
    I am wondering if this is the best way to do this. I have about 500 threads that run indefinitely, but Thread.sleep for a minute when done one cycle of processing. ExecutorService es = Executors.newFixedThreadPool(list.size()+1); for (int i = 0; i < list.size(); i++) { es.execute(coreAppVector.elementAt(i)); //coreAppVector is a vector of extends thread objects } I do need a separate threads for each running task, so changing the architecture isn't an option. I tried making my threadPool size equal to Runtime.getRuntime().availableProcessors() which attempted to run all 500 threads, but only let 8 (4xhyperthreading) of them execute. The other threads wouldn't surrender and let other threads have their turn. I tried putting in a wait() and notify(), but still no luck. If anyone has a simple example or some tips, I would be grateful!

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  • Java - How can I edit the size and position of a button using Swing?

    - by mino
    I have the following code but I'd like to structure several buttons of certain sizes. I'm just wondering how to do this as I've Googled it and found several different methods but none seem to work. Any advice? import javax.swing.*; public class GUI { public static void main(String[] args) { JFrame window = new JFrame(); window.setSize(500, 500); window.setTitle("My Application"); JButton button = new JButton("click me"); window.add(button); window.setVisible(true); } }

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