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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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  • DataSource or ConnectionPoolDataSource for Application Server JDBC resources

    - by Vinnie
    When creating JNDI JDBC connection pools in an application server, I always specified the type as javax.sql.ConnectionPoolDataSource. I never really gave it too much thought as it always seemed natural to prefer pooled connections over non-pooled. However, in looking at some examples (specifically for Tomcat) I noticed that they specify javax.sql.DataSource. Further, it seems there are settings for maxIdle and maxWait giving the impression that these connections are pooled as well. Glassfish also allows these parameters regardless of the type of data source selected. Are javax.sql.DataSource pooled in an application server (or servlet container)? What (if any) advantages are there for choosing javax.sql.ConnectionPoolDataSource over javax.sql.DataSource (or vice versa)?

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  • JCombobox containing enum values inside a table

    - by Edan
    Hello, I have a class containing Enum with values. (names) In other class I would like to enter inside a table a cell type of JCombobox that will use these enums values. my problem is to combain between string values and the enum. for example the enum class: enum item_Type {entree, main_Meal, Dessert, Drink} for example the table class: setTitle("Add new item" ); setSize(300, 80); setBackground( Color.gray ); // Create a panel to hold all other components topPanel = new JPanel(); topPanel.setLayout( new BorderLayout() ); getContentPane().add( topPanel ); //new JComboBox(item_Type.values()); JComboBox aaa = new JComboBox(); aaa = new JComboBox(item_Type.values()); TableColumn sportColumn = table.getColumnModel().getColumn(2); // Create columns names String columnNames[] = {"Item Description", "Item Type", "Item Price"}; // Create some data String dataValues[][] = {{ "0", aaa, "0" }}; // Create a new table instance table = new JTable( dataValues, columnNames ); // Add the table to a scrolling pane scrollPane = new JScrollPane( table ); topPanel.add( scrollPane, BorderLayout.CENTER ); I know that at the dataValues array I cant use aaa (the enum jcombobox). How can I do that? thanks in advance.

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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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  • OO vs Simplicity when it comes to user interaction

    - by Oetzi
    Firstly, sorry if this question is rather vague but it's something I'd really like an answer to. As a project over summer while I have some downtime from Uni I am going to build a monopoly game. This question is more about the general idea of the problem however, rather than the specific task I'm trying to carry out. I decided to build this with a bottom up approach, creating just movement around a forty space board and then moving on to interaction with spaces. I realised that I was quite unsure of the best way of proceeding with this and I am torn between two design ideas: Giving every space its own object, all sub-classes of a Space object so the interaction can be defined by the space object itself. I could do this by implementing different land() methods for each type of space. Only giving the Properties and Utilities (as each property has unique features) objects and creating methods for dealing with the buying/renting etc in the main class of the program (or Board as I'm calling it). Spaces like go and super tax could be implemented by a small set of conditionals checking to see if player is on a special space. Option 1 is obviously the OO (and I feel the correct) way of doing things but I'd like to only have to handle user interaction from the programs main class. In other words, I don't want the space objects to be interacting with the player. Why? Errr. A lot of the coding I've done thus far has had this simplicity but I'm not sure if this is a pipe dream or not for larger projects. Should I really be handling user interaction in an entirely separate class? As you can see I am quite confused about this situation. Is there some way round this? And, does anyone have any advice on practical OO design that could help in general?

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  • How to get a Class literal from a generically specific Class

    - by h2g2java
    There are methods like these which require Class literals as argument. Collection<EmpInfo> emps = SomeSqlUtil.select( EmpInfo.class, "select * from emps"); or GWT.create(Razmataz.class); The problem presents itself when I need to supply generic specific classes like EmpInfo<String> Razmataz<Integer> The following would be wrong syntax Collection<EmpInfo<String>> emps = SomeSqlUtil.select( EmpInfo<String>.class, "select * from emps"); or GWT.create(Razmataz<Integer>.class); Because you cannot do syntax like Razmataz<Integer>.class So, how would I be able to squeeze a class literal out of EmpInfo<String> Razmataz<Integer> so that I could feed them as arguments to methods requiring Class literals? Further info Okay, I confess that I am asking this primarily for GWT. I have a pair of GWT RPC interface Razmataz. (FYI, GWT RPC interface has to be defined in server-client pairs). I plan to use the same interface pair for communicating whether it be String, Integer, Boolean, etc. GWT.create(Razmataz) for Razmataz<T> complains that, since I did not specify T, GWT compiler treated it as Object. Then GWT compiler would not accept Object class. It needs to be more specific than being an Object. So, it seems there is no way for me to tell GWT.create what T is because a Class literal is a runtime concept while generics is a compile time concept, Right?

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  • What web UI framework is most suitable for building dynamic pages / forms?

    - by waxwing
    Hello, We are at a stage where we are considering different Web UI frameworks (most likely component based ones such as GWT, JSF, Wicket, Vaadin, etc). One of the main use cases / constraints is that it must support generating dynamic pages. I.e., the page/form layout and components is stored in a database and is changeable at runtime, and from this pages are generated. We are also going to write static layouts, but that is not the main focus of this question. I thought maybe the user community here can share experiences of different frameworks in this context. Are there differences in ease of implementation and what is suitable?

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  • Handle Transaction on differents EARs

    - by rfders
    Hello, what is the best practice to handle multiple EARs and the same transaction, as far as we know we need to apply XA concepts in order transaction works correctly. but apparently in currents project that we've been working on, this is not strictly necessary for creates and updates; however if we try to retrieve any collection from an entity we get an error that say there its not an active transaction or it was closed, but if we update Entity A in Ear A and update Entity B in Ear B it works perfectly when Entity A and Entity B has different datasources, at this point we are so confused about that, because we haven't configure any xa datasource yet. how is the best approach to work with this. transaction are handles by beans and not by the container and datasource are different between EAR A and EAR B

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  • Cast object to interface when created via reflection

    - by Al
    I'm trying some stuff out in Android and I'm stuck at when trying to cast a class in another .apk to my interface. I have the interface and various classes in other .apks that implement that interface. I find the other classes using PackageManager's query methods and use Application#createPackageContext() to get the classloader for that context. I then load the class, create a new instance and try to cast it to my interface, which I know it definitely implements. When I try to cast, it throws a class cast exception. I tried various things like loading the interface first, using Class#asSubclass, etc, none of which work. Class#getInterfaces() shows the interface is implemented. My code is below: PackageManager pm = getPackageManager(); List<ResolveInfo> lr = pm.queryIntentServices(new Intent("com.example.some.action"), 0); ArrayList<MyInterface> list = new ArrayList<MyInterface>(); for (ResolveInfo r : lr) { try { Context c = getApplication().createPackageContext(r.serviceInfo.packageName, Context.CONTEXT_IGNORE_SECURITY | Context.CONTEXT_INCLUDE_CODE); ClassLoader cl = c.getClassLoader(); String className = r.serviceInfo.name; if (className != null) { try { Class<?> cls = cl.loadClass(className); Object o = cls.newInstance(); if (o instanceof MyInterface) { //fails list.add((MyInterface) o); } } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } // some exceptions removed for readability } } catch (NameNotFoundException e1) { e1.printStackTrace(); }

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  • Counting down to zero in contrast to counting up to length - 1

    - by Helper Method
    Is it recommended to count in small loops (where possible) down from length - 1 to zero instead of counting up to length - 1? 1.) Counting down for (int i = a.length - 1; i >= 0; i--) { if (a[i] == key) return i; } 2.) Counting up for (int i = 0; i < a.length; i++) { if (a[i] == key) return i; } The first one is slightly faster that the second one (because comparing to zero is faster) but is a little more error-prone in my opinion. Besides, the first one could maybe not be optimized by future improvements of the JVM. Any ideas on that?

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  • Partially constructed object / Multi threading

    - by reto
    Heya! I'm using joda due to it's good reputation regarding multi threading. It goes great distances to make multi threaded date handling efficient, for example by making all Date/Time/DateTime objects immutable. But here's a situation where I'm not sure if Joda is really doing the right thing. It probably is correct, but I'd be very interested to see the explanation for it. When a toString() of a DateTime is being called Joda does the following: /* org.joda.time.base.AbstractInstant */ public String toString() { return ISODateTimeFormat.dateTime().print(this); } All formatters are thread safe, as they are as well ready-only. But what's about the formatter-factory: private static DateTimeFormatter dt; /* org.joda.time.format.ISODateTimeFormat */ public static DateTimeFormatter dateTime() { if (dt == null) { dt = new DateTimeFormatterBuilder() .append(date()) .append(tTime()) .toFormatter(); } return dt; } This is a common pattern in single threaded applications. I see the following dangers: Race condition during null check -- worst case: two objects get created. No Problem, as this is solely a helper object (unlike a normal singleton pattern situation), one gets saved in dt, the other is lost and will be garbage collected sooner or later. the static variable might point to a partially constructed object before the objec has been finished initialization (before calling me crazy, read about a similar situation in this Wikipedia article. So how does Joda ensure that not partially created formatter gets published in this static variable? Thanks for your explanations! Reto

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  • How to click through JGlassPane With MouseListener to UI behind it

    - by Epicmaster
    I have a JFrame and a bunch of JComponents on top of the JFrame. I need to make use of the JGlassPane and I used this implementation to set it up. JPanel glass = new JPanel(); frame.setGlassPane(glass); glass.setVisible(true); glass.setOpaque(false); After doing so I can't select any JButtons or other JComponents under the JGlassPane. Is there a way to have only the components on the GlassPane selectable while still having the ability to select components under the GlassPane? Edit I forgot to mention (not knowing this would be relevant) that I did attach both a MouseListener and a MouseMotionListener to the glass pane. Is there a way to pass the Mouse Events to other components and only use them when needed?

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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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  • Can the JVM recover from an OutOfMemoryError without a restart

    - by askullhead
    Can the JVM recover from an OutOfMemoryError without a restart if it gets a chance to run the GC before more object allocation requests come in? Do the various JVM implementations differ in this aspect? EDIT: My question was about the JVM recovering and not the user program trying to recover by catching the error. In other words if an OOME is thrown in an application server (jboss/websphere/..) do I have to restart it? Or can I let it run if further requests seem to work without a problem. Sorry if that wan't clear.

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  • @NamedQuery select parameter meaning

    - by sergionni
    Found some examples of @NamedQuery annotations,e.g.: @NamedQuery(name="employeeBySsn" query="select e from Employee e where e.ssn = :ssn") what does parameter e mean? the second usage of it seems like alias name of table and what does "select e" part mean?

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  • Loading velocity template inside a jar file

    - by Rafael
    I have a project where I want to load a velocity template to complete it with parameters. The whole application is packaged as a jar file. What I initially thought of doing was this: VelocityEngine ve = new VelocityEngine(); URL url = this.getClass().getResource("/templates/"); File file = new File(url.getFile()); ve = new VelocityEngine(); ve.setProperty(RuntimeConstants.RESOURCE_LOADER, "file"); ve.setProperty(RuntimeConstants.FILE_RESOURCE_LOADER_PATH, file.getAbsolutePath()); ve.setProperty(RuntimeConstants.FILE_RESOURCE_LOADER_CACHE, "true"); ve.init(); VelocityContext context = new VelocityContext(); if (properties != null) { stringfyNulls(properties); for (Map.Entry<String, Object> property : properties.entrySet()) { context.put(property.getKey(), property.getValue()); } } final String templatePath = templateName + ".vm"; Template template = ve.getTemplate(templatePath, "UTF-8"); String outFileName = File.createTempFile("p2d_report", ".html").getAbsolutePath(); BufferedWriter writer = new BufferedWriter(new FileWriter(new File(outFileName))); template.merge(context, writer); writer.flush(); writer.close(); And this works fine when I run it in eclipse. However, once I package the program and try to run it using the command line I get an error because the file could not be found. I imagine the problem is in this line: ve.setProperty(RuntimeConstants.FILE_RESOURCE_LOADER_PATH, file.getAbsolutePath()); Because in a jar the absolute file does not exist, since it's inside a zip, but I couldn't yet find a better way to do it. Anyone has any ideas?

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  • Google App Engine - What causes cold start latency time to be high, even though my CPU usage is rela

    - by Spines
    I've optimized my code to use only lightweight libraries. I'm even using the low level datastore rather than JDO. And my cold start CPU usage has dropped from about 5 seconds to about 1.5 seconds. However, the time it takes to respond is often about 4.5 seconds, though it varies a lot. Here are some lines from my logs: 03-19 09:16PM 57.368 /donothing 200 4506ms 1516cpu_ms 0kb Mozilla/5.0 03-19 09:22PM 54.884 /donothing 200 4452ms 1477cpu_ms 0kb Mozilla/5.0 What is the app engine doing for those extra 3 seconds that apparently isn't using any CPU?

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  • Android map overly transparency has unwanted gradient

    - by DavidP2190
    I'm a making my first android app and for part of it I need some shaded areas over a mapview. I've got this working so far but the when I set the alpha of the fill colour, it goes strange. I'm not allowed to post images yet, but you can see what happens here: http://i.imgur.com/leXmc.png I'm not sure what causes it, but here is some code from where it gets drawn. public boolean draw(Canvas canvas, MapView mapView, boolean shadow, long when) { Paint paint = new Paint(); paint.setStrokeWidth(2); paint.setColor(android.graphics.Color.GREEN); paint.setStyle(Paint.Style.FILL_AND_STROKE); paint.setAlpha(25); screenPoints = new Point[10]; Path path = new Path(); for (int x = 0; x<greenZone.length; x++){ screenPoints[x] = new Point(); mapView.getProjection().toPixels(greenZone[x], screenPoints[x]); } path.moveTo(screenPoints[0].x, screenPoints[0].y); for (int x = 1; x < screenPoints.length-1; x++){ paint.setAlpha(25); if (x<9){ path.lineTo(screenPoints[x].x, screenPoints[x].y); canvas.drawPath(path, paint); } else{ path.moveTo(screenPoints[screenPoints.length-1].x, screenPoints[screenPoints.length-1].y); path.lineTo(screenPoints[0].x, screenPoints[0].y); canvas.drawPath(path, paint); } } return true; } Thanks.

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  • Can a user-chosen image be inserted directly into a JEditorPane?

    - by JIM
    What I am trying to do is open up a JFilechooser that filters jpeg,gif and png images, then gets the user's selection and inserts it into the JEditorPane. Can this be done? or am i attempting something impossible? Here is a sample of my program.(insert is a JMenuItem and mainText is a JEditorPane) insert.addActionListener(new ActionListener(){ public void actionPerformed(ActionEvent e){ JFileChooser imageChooser = new JFileChooser(); imageChooser.setFileFilter(new FileNameExtensionFilter("Image Format","jpg","jpeg","gif","png")); int choice = imageChooser.showOpenDialog(mainText); if (choice == JFileChooser.APPROVE_OPTION) { mainText.add(imageChooser.getSelectedFile()); } } }); What i tried to do is use the add method, i know it's wrong but just to give you an idea of what i'm trying to do. Before you complain, i'm sorry about the code formatting, i don't really know all the conventions of what is considered good or bad style. Thank you very much.

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