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  • How do I implement a listener pattern over RMI using Spring?

    - by predhme
    So here is a generalized version of our application desgin: @Controller public class MyController { @Autowired private MyServiceInterface myServiceInterface; @RequestMapping("/myURL") public @ResponseBody String doSomething() { MyListenerInterface listener = new MyListenerInterfaceImpl(); myServiceInterface.doThenCallListener(listener); // do post stuff } } public interface MyListenerInterface { public void callA(); public void callB(); } public class MyListenerInterfaceImpl implements MyListenerInterface { // ... omitted for clarity } public interface MyServiceInterface { public void doThenCallListener(MyListenerInterface listener); } public class MyServiceImpl { public void doThenCallListener(MyListenerInterface listener) { // do stuff listener.callA(); } } Basically I have a controller that is being called via AJAX in which I am looking to return a response as a string. However, I need to make a call to the backend (MyServiceInterface). That guy is exposed through RMI by using Spring (man that was easy). But the service method as described requires a listener to be registered for invokation completion purposes. So what I assume I need to achieve is transparently to the backend make it so that when the listener methods are called, really the call is going over RMI. I would have thought Spring would have a simple way to wrap a POJO (not a service singleton) with RMI calls. I looked through their documentation but they had nothing besides exposing services via RMI. Could someone point me in the right direction?

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  • JTable custom cell renderer to create row header

    - by hhj
    Can somebody please explain how I would create row headers? I already have the data and header texts set in the JTable: all I want to know is how I can use a cell renderer to take that first column (i.e. the row header column) and make it look like the column headers (i.e. the first row). Right now its background is white, so it looks like regular data. I want it to appear gray (or non-opaque I guess??). Oh and it should also not be selectable. Thanks.

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  • Recursion Question : Revision

    - by stan
    My slides say that: A recursive call should always be on a smaller data structure than the current one There must be a non recursive option if the data structure is too small You need a wrapper method to make the recursive method accessible Just reading this from the slides makes no sense, especially seeing as it was a topic from before christmas! Could anyone try and clear up what it means please? Thank you

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  • Change classloader

    - by Chris
    I'm trying to switch the class loader at runtime: public class Test { public static void main(String[] args) throws Exception { final InjectingClassLoader classLoader = new InjectingClassLoader(); Thread.currentThread().setContextClassLoader(classLoader); Thread thread = new Thread("test") { public void run() { System.out.println("running..."); // approach 1 ClassLoader cl = TestProxy.class.getClassLoader(); try { Class c = classLoader.loadClass("classloader.TestProxy"); Object o = c.newInstance(); c.getMethod("test", new Class[] {}).invoke(o); } catch (Exception e) { e.printStackTrace(); } // approach 2 new TestProxy().test(); }; }; thread.setContextClassLoader(classLoader); thread.start(); } } and: public class TestProxy { public void test() { ClassLoader tcl = Thread.currentThread().getContextClassLoader(); ClassLoader ccl = ClassToLoad.class.getClassLoader(); ClassToLoad classToLoad = new ClassToLoad(); } } (it is not relevant what the InjectingClassLoader is) I'd like to make the result of "approach 1" and "approach 2" exactly same, but it looks like thread.setContextClassLoader(classLoader) does nothing and the "approach 2" always uses the system classloader (can be determined by comparing tcl and ccl variables while debugging). Is it possible to make all classes loaded by new thread use given classloader?

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  • hibernate for dynamic table creation

    - by user369316
    i AM A HIBERNATE BEGINNER ,Since i need to create dynamic tables with dynamic fields in them i chose to use hibernate . As far as my understanding , creating tables requires a class with the fields defined in the class . How do i generate the classes dynamically based on the table with the required fields ?

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  • JUnit Test method with randomized nature

    - by Peter
    Hey, I'm working on a small project for myself at the moment and I'm using it as an opportunity to get acquainted with unit testing and maintaining proper documentation. I have a Deck class with represents a deck of cards (it's very simple and, to be honest, I can be sure that it works without a unit test, but like I said I'm getting used to using unit tests) and it has a shuffle() method which changes the order of the cards in the deck. The implementation is very simple and will certainly work: public void shuffle() { Collections.shuffle(this.cards); } But, how could I implement a unit test for this method. My first thought was to check if the top card of the deck was different after calling shuffle() but there is of course the possibility that it would be the same. My second thought was to check if the entire order of cards has changed, but again they could possibly be in the same order. So, how could I write a test that ensures this method works in all cases? And, in general, how can you unit test methods for which the outcome depends on some randomness? Cheers, Pete

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  • fail-fast iterator

    - by joy
    I get this definition : As name suggest fail-fast Iterators fail as soon as they realized that structure of Collection has been changed since iteration has begun. what it mean by since iteration has begun? is that mean after Iterator it=set.iterator() this line of code? public static void customize(BufferedReader br) throws IOException{ Set<String> set=new HashSet<String>(); // Actual type parameter added **Iterator it=set.iterator();**

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  • JTree keep expanding problem

    - by newbie123
    I want to keep my jTree file expanded. I using below code to expand the jTree : public void expandAll(JTree tree) { int row = 0; while (row < tree.getRowCount()) { tree.expandRow(row); row++; } } It works, but when I add in new file or delete file the jtree collapse back. How can keep the jTree expanded?

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  • Source code versioning with comments (organizational practice) - leave or remove?

    - by ADTC
    Before you start admonishing me with "DON'T DO IT," "BAD PRACTICE!" and "Learn to use proper source code control", please hear me out first. I am fully aware that the practice of commenting out old code and leaving it there forever is very bad and I hate such practice myself. But here's the situation I'm in. A few months ago I joined a company as software developer. I had worked in the company for few months as an intern, about a year before joining recently. Our company uses source code version control (CVS) but not properly. Here's what happened both in my internship and my current permanent position. Each time I was assigned to work on a project (legacy, about 8-10 years old). Instead of creating a CVS account and letting me check out code and check in changes, a senior colleague exported the code from CVS, zipped it up and passed it to me. While this colleague checks in all changes in bulk every few weeks, our usual practice is to do fine-grained versioning in the actual source code itself (each file increments in versions independent from the rest). Whenever a change is made to a file, old code is commented out, new code entered below it, and this whole section is marked with a version number. Finally a note about the changes is placed at the top of the file in a section called Modification History. Finally the changed files are placed in a shared folder, ready and waiting for the bulk check-in. /* * Copyright notice blah blah * Some details about file (project name, file name etc) * Modification History: * Date Version Modified By Description * 2012-10-15 1.0 Joey Initial creation * 2012-10-22 1.1 Chandler Replaced old code with new code */ code .... //v1.1 start //old code new code //v1.1 end code .... Now the problem is this. In the project I'm working on, I needed to copy some new source code files from another project (new in the sense that they didn't exist in destination project before). These files have a lot of historical commented out code and comment-based versioning including usually long or very long Modification History section. Since the files are new to this project I decided to clean them up and remove unnecessary code including historical code, and start fresh at version 1.0. (I still have to continue the practice of comment-based versioning despite hating it. And don't ask why not start at version 0.1...) I have done similar something during my internship and no one said anything. My supervisor has seen the work a few times and didn't say I shouldn't do such clean-up (if at all it was noticed). But a same-level colleague saw this and said it's not recommended as it may cause downtime in the future and increase maintenance costs. An example is when changes are made in another project on the original files and these changes need to be propagated to this project. With code files drastically different, it could cause confusion to an employee doing the propagation. It makes sense to me, and is a valid point. I couldn't find any reason to do my clean-up other than the inconvenience of a ridiculously messy code. So, long story short: Given the practice in our company, should I not do such clean-up when copying new files from project to project? Is it better to make changes on the (copy of) original code with full history in comments? Or what justification can I give for doing the clean-up? PS to mods: Hope you allow this question some time even if for any reason you determine it to be unfit in SO. I apologize in advance if anything is inappropriate including tags.

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  • Need to map classes to different databases at runtime in Hibernate

    - by serg555
    I have MainDB database and unknown number (at compile time) of UserDB_1, ..., UserDB_N databases. MainDB contains names of those UserDB databases in some table (new UserDB can be created at runtime). All UserDB have exactly the same table names and fields. How to handle such situation in Hibernate? (database structure cannot be changed). Currently I am planning to create generic User classes not mapped to anything and just use native SQL for all queries: session.createSQLQuery("select * from " + db + ".user where id=1") .setResultTransformer(Transformers.aliasToBean(User.class)); Is there anything better I can do? Ideally I would want to have mappings for UserDB tables and relations and use HQL on required database.

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  • Configurable Values in Enum

    - by Omer Akhter
    I often use this design in my code to maintain configurable values. Consider this code: public enum Options { REGEX_STRING("Some Regex"), REGEX_PATTERN(Pattern.compile(REGEX_STRING.getString()), false), THREAD_COUNT(2), OPTIONS_PATH("options.config", false), DEBUG(true), ALWAYS_SAVE_OPTIONS(true), THREAD_WAIT_MILLIS(1000); Object value; boolean saveValue = true; private Options(Object value) { this.value = value; } private Options(Object value, boolean saveValue) { this.value = value; this.saveValue = saveValue; } public void setValue(Object value) { this.value = value; } public Object getValue() { return value; } public String getString() { return value.toString(); } public boolean getBoolean() { Boolean booleanValue = (value instanceof Boolean) ? (Boolean) value : null; if (value == null) { try { booleanValue = Boolean.valueOf(value.toString()); } catch (Throwable t) { } } // We want a NullPointerException here return booleanValue.booleanValue(); } public int getInteger() { Integer integerValue = (value instanceof Number) ? ((Number) value).intValue() : null; if (integerValue == null) { try { integerValue = Integer.valueOf(value.toString()); } catch (Throwable t) { } } return integerValue.intValue(); } public float getFloat() { Float floatValue = (value instanceof Number) ? ((Number) value).floatValue() : null; if (floatValue == null) { try { floatValue = Float.valueOf(value.toString()); } catch (Throwable t) { } } return floatValue.floatValue(); } public static void saveToFile(String path) throws IOException { FileWriter fw = new FileWriter(path); Properties properties = new Properties(); for (Options option : Options.values()) { if (option.saveValue) { properties.setProperty(option.name(), option.getString()); } } if (DEBUG.getBoolean()) { properties.list(System.out); } properties.store(fw, null); } public static void loadFromFile(String path) throws IOException { FileReader fr = new FileReader(path); Properties properties = new Properties(); properties.load(fr); if (DEBUG.getBoolean()) { properties.list(System.out); } Object value = null; for (Options option : Options.values()) { if (option.saveValue) { Class<?> clazz = option.value.getClass(); try { if (String.class.equals(clazz)) { value = properties.getProperty(option.name()); } else { value = clazz.getConstructor(String.class).newInstance(properties.getProperty(option.name())); } } catch (NoSuchMethodException ex) { Debug.log(ex); } catch (InstantiationException ex) { Debug.log(ex); } catch (IllegalAccessException ex) { Debug.log(ex); } catch (IllegalArgumentException ex) { Debug.log(ex); } catch (InvocationTargetException ex) { Debug.log(ex); } if (value != null) { option.setValue(value); } } } } } This way, I can save and retrieve values from files easily. The problem is that I don't want to repeat this code everywhere. Like as we know, enums can't be extended; so wherever I use this, I have to put all these methods there. I want only to declare the values and that if they should be persisted. No method definitions each time; any ideas?

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  • JFrame that has multiple layers

    - by phunehehe
    Hello, I have a window that has two layers: a static background and a foreground that contains moving objects. My idea is to draw the background just once (because it's not going to change), so I make the changing panel transparent and add it on top of the static background. Here is the code for this: public static void main(String[] args) { JPanel changingPanel = new JPanel() { @Override public void paintComponent(Graphics g) { super.paintComponent(g); g.setColor(Color.RED); g.fillRect(100, 100, 100, 100); } }; changingPanel.setOpaque(false); JPanel staticPanel = new JPanel(); staticPanel.setBackground(Color.BLUE); staticPanel.setLayout(new BorderLayout()); staticPanel.add(changingPanel); JFrame frame = new JFrame(); frame.add(staticPanel); frame.setSize(800, 600); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); } This piece of code gives me the correct image I want, but every time I repaint changingPanel, staticPanel gets repainted as well (which is obviously against the whole idea of painting the static panel just once). Can somebody show me what's wrong? FYI I am using the javax.swing.Timer to recalculate and repaint the changing panel 24 times every second.

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  • How to access private static target field in aspect in AspectJ?

    - by LihO
    I have a simple class Main with private static int x and an aspect that should output the old value of x before it is reassigned: public class Main { private static int x; public static void main(String[] args) { foo(7); } public static void foo(int y) { x = y; } } and MonitorX.aj: public aspect MonitorX { before() : set(static int Main.x){ System.out.println(Main.x); } } which doesn't work since I can't access private x using Main.x. I've also tried: before(int t) : set(static int Main.x) && target(t){ System.out.println(t); } which doesn't work either (nothing is outputted, if I try to output string, it seems that the aspect isn't invoked at all). However printing out the new value that is being assigned works: before(int newVal) : set(static int Main.x) && args(newVal){ System.out.println(newVal); } What am I missing?

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