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  • Paint java GUI component to image file

    - by Simon
    Let's say I have JButton test = new JButton("Test Button"); and I want to draw the button into an image object and save it to a file. I tried this: BufferedImage b = new BufferedImage(500, 500, BufferedImage.TYPE_INT_ARGB); test.paint(b.createGraphics()); File output = new File("C:\\screenie.png"); try { ImageIO.write(b, "png", output); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } This code produced an empty 500x500 PNG-file. Does anyone know how I can draw the GUI component to an image file?

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  • Java Interfaces

    - by Mandar
    I have a doubt.. Why do we need interfaces ? Can't we acheive the same effect by writing the implementation directly in the class? It would be great if you could illustrate your point with an example. Thanks in advance.

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  • Java EE deployment error

    - by Rajesh
    While deploying a particular project I'm getting deployment error like "module has not been deployed"... but I'm able to deploy other projects... the error shown is as follows In-place deployment at F:\onlineexam_1\build\web deploy?path=F:\onlineexam_1\build\web&name=onlineexam_1&force=true failed on GlassFish v3 Domain F:\onlineexam_1\nbproject\build-impl.xml:577: The module has not been deployed. BUILD FAILED (total time: 3 seconds)

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  • Passing Interface Class as a Parameter in Java

    - by aleclerc
    I have an interface: public interface IMech { } and a class that implements it public class Email implements IMech { } and a third class that has this method implemented: public void sendNotification( Class< IMech > mechanism ){ } now I'm trying to call that method like so foo.sendNotification(Email.class); but i keep getting an exception saying: The method sendNotification(Class<IMechanism>) in the type RemediationOperator is not applicable for the arguments (Class<EmailNotification>) Shouldn't this work if it interfaces that class?

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  • How can i zip files in Java and not include files paths

    - by Ignacio
    For example, i want to zip a file stored in /Users/me/Desktop/image.jpg I maded this method: public static Boolean generateZipFile(ArrayList<String> sourcesFilenames, String destinationDir, String zipFilename){ // Create a buffer for reading the files byte[] buf = new byte[1024]; try { // VER SI HAY QUE CREAR EL ROOT PATH boolean result = (new File(destinationDir)).mkdirs(); String zipFullFilename = destinationDir + "/" + zipFilename ; System.out.println(result); // Create the ZIP file ZipOutputStream out = new ZipOutputStream(new FileOutputStream(zipFullFilename)); // Compress the files for (String filename: sourcesFilenames) { FileInputStream in = new FileInputStream(filename); // Add ZIP entry to output stream. out.putNextEntry(new ZipEntry(filename)); // Transfer bytes from the file to the ZIP file int len; while ((len = in.read(buf)) > 0) { out.write(buf, 0, len); } // Complete the entry out.closeEntry(); in.close(); } // Complete the ZIP file out.close(); return true; } catch (IOException e) { return false; } } But when i extract the file, the unzipped files have the full path. I don't want the full path of each file in the zip i only want the filename. How can i made this?

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  • Fastest Java web templating language

    - by CaptainAwesomePants
    I'm about to start in on a new Spring MVC project, and I'm examining the various options for the view. I've never been a fan of JSP, and I've run into JSP-related performance problems in the past, so I was looking through the other options. I'm hoping that somewhere somebody's taken a census of the various options (maybe it'll have to be me) and pronounced which ones are quick, or at least which options there are. Here are the choices I've thought of, ordered from obvious to bizarre: JSP, JSTL Velocity FreeMarker GSP (Groovy JSP) ERB powered by IronRuby or some such craziness Tea Any suggestions, personal preferences, or other good options for the list?

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  • http streaming using java servlet

    - by Shamik
    I have a servlet based web application which produces two sets of data. One set of data in the webpage which is essential and other set which is optional. I would like to render the essential data as fast as possible and then stream the optional data. I was thinking of writing the essential data to the output stream of HttpServletRequest and then call HttpServletRequest.flushBuffer() to commit the response to the client, but do not return from the servlet code, but instead create the optional data , write that to the outputstream again and then return from servlet code. What are the things that could go wrong in this scheme ? Is this a standard practice to achieve this goal?

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  • What are the essential Java libraries and utilities for a returning dynamic language user?

    - by jbwiv
    Guys, Long time Java developer here, but I've spent more time working with Ruby over the past 3 years or so as far as web applications go. I really have enjoyed it, but there are concerns I've uncovered that I won't cover here. Now that I've found the Play! framework, I'm thrilled about the prospect of having a Rails-like experience with Java's speed and reliability. Aside from what Play! provides out of the box, I'm looking for recommendations on "can't miss" libraries and tools for the Java developer used to pragmatic, dynamic experiences. I've found Project Lombok, which looks like a very intriguing way to eliminate a lot of the boiler plate, unnecessary Java noise. What else should I know about? I know Google has released quite a few libraries over the past three years that I've heard mentioned on the Java Posse, but I can't recall exactly what they are. I'm sure I've missed others in my absence. So, what makes up your essential Java toolbox these days? Thanks for your answers!

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  • Java Web Application on Tomcat - Displaying a File Uploaded by User

    - by walnutmon
    I need to display uploaded files on a web application, the flow is as follows User uploads file through web UI Validation on image Makes call to imageRepository.store( uploadedImage, user.getSite() ) The user wants the image displayed which adds <img src="${anUploadedImage.getUrl()}"/> but that is where I'm stuck, what can getUrl() do? The simple solution is to put it someplace and let Apache serve the file, but then I can't use the application to ensure that one user isn't modifying the URL to view other users files, which in this case is important

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  • Bluetooth in Java Mobile: Handling connections that go out of range

    - by Albus Dumbledore
    I am trying to implement a server-client connection over the spp. After initializing the server, I start a thread that first listens for clients and then receives data from them. It looks like that: public final void run() { while (alive) { try { /* * Await client connection */ System.out.println("Awaiting client connection..."); client = server.acceptAndOpen(); /* * Start receiving data */ int read; byte[] buffer = new byte[128]; DataInputStream receive = client.openDataInputStream(); try { while ((read = receive.read(buffer)) > 0) { System.out.println("[Recieved]: " + new String(buffer, 0, read)); if (!alive) { return; } } } finally { System.out.println("Closing connection..."); receive.close(); } } catch (IOException e){ e.printStackTrace(); } } } It's working fine for I am able to receive messages. What's troubling me is how would the thread eventually die when a device goes out of range? Firstly, the call to receive.read(buffer) blocks so that the thread waits until it receives any data. If the device goes out of range, it would never proceed onward to check if meanwhile it has been interrupted. Secondly, it would never close the connection, i.e. the server would not accept the device once it goes back in range. Thanks! Any ideas would be highly appreciated! Merry Christmas!

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  • Unique serial number in a java web application.

    - by Zenzen
    I've been wondering what's the correct practice for generating unique ids? The thing is in my web app I'll have a plugin system, when a user registers a plugin I want to generate a unique serial ID for it. I've been thinking about storing all numbers in a DB or a file on the server, generating a random number and checking whether it already exists in the DB/file, but that doesn't seem that good. Are there other ways to do it? Would using the UUID be the preferred way to go?

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  • Do we need seperate file path for window and linux in java

    - by Kishor Sharma
    I have a file on linux ubuntu server hosted with path name /home/kishor/project/detail/. When I made a web app in window to upload and download file from specified location i used path "c:\kishor\projects\detail\" for saving in window. For my surprise when i used window file path name in my server i am still able to get files and upload them, i.e, "c:\kishor\projects\detail\". Can anyone explain why it is working (as window and linux both use different file path pattern).

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  • Best OpenID library for Java

    - by Adam Crume
    I want users to be able to log into my website with OpenID, but I don't know which library to use. I know which ones are out there, but I would like to know which one would be best. I'm running JOnAS, but no web framework (no Spring, Struts, GWT, etc.). (Please don't chastise me for not using a web framework. I have my reasons.) For what it's worth, my web site is broken into multiple WARs, and I would prefer something that works well in that situation, but that's not a big deal. Does anyone have experience with the different libraries? Any experiences or wisdom you can share?

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  • Implementing OAuth protocol in Java

    - by Wasim
    Hi all , I'm looking for an open source library that implements the OAuth protocol , I need the server side implementation . Say I have a Social network system , and I want to give my users an OAth abiliy to my API , like facebook. Do you have any suggestion , sure examples . Thanks in advance ...

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  • Java Executor: Small tasks or big ones?

    - by Arash Shahkar
    Consider one big task which could be broken into hundreds of small, independently-runnable tasks. To be more specific, each small task is to send a light network request and decide upon the answer received from the server. These small tasks are not expected to take longer than a second, and involve a few servers in total. I have in mind two approaches to implement this using the Executor framework, and I want to know which one's better and why. Create a few, say 5 to 10 tasks each involving doing a bunch of send and receives. Create a single task (Callable or Runnable) for each send & receive and schedule all of them (hundreds) to be run by the executor. I'm sorry if my question shows that I'm lazy to test these and see for myself what's better (at least performance-wise). My question, while looking after an answer to this specific case, has a more general aspect. In situations like these when you want to use an executor to do all the scheduling and other stuff, is it better to create lots of small tasks or to group those into a less number of bigger tasks?

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  • Dealing With Java Default Level Access Specifiers

    - by Tom Tresansky
    I've seen some code in a project recently where some fields in a couple classes have been using the default access modifier without good reason to. It almost looks like a case of "oops, forgot to make these private". Since the classes are used almost exclusively outside of the package they are defined in, the fields are not visible from the calling code, and are treated as private. So the mistake/oversight would not be very noticeable. However, encapsulation is broken. If I wanted to add a new class to the existing package, I could then mess with internal data in objects using fields with default access. So, my questions: Are there any best practices concerning default access specifiers that I should be aware of? Anything that would help prevent this type of accident from re-occurring? Are are any annotations which might say something to the effect of "I really meant for these to be default access"? Using CheckStyle, or any other Eclipse plugins, is there any way to flag instances of default fields, or disallow any not accompanied by, say, a "//default access" comment trailing them?

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  • Java - How to change context root of a dynamic web project in eclipse

    - by Yatendra Goel
    I have developed a dynamic web project in eclipse. Now I can access it through my browser using the following url: http://localhost:8080/MyDynamicWebApp Now I want to change the access url to http://localhost:8080/app I changed the context root from the project properties | Web Project Settings | Context Root But it is not working. The web app still has the access url as earlier. I have re-deployed the application on tomcat, re-started the tomcat and have done everything that should be done but the access url is the same as earlier. I found that there were no server.xml file attached with the WARfile. The how the tomcat is determining that the context root of my web app is /MyDynamicWebApp and is allowing me to access the application through that url

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  • How to avoid resetting the java Scanner position

    - by Derek
    I have some code that looks more or less like this: while(scanner.hasNext()) { if(scanner.findInLine("Test") !=null) { //do some things }else{ scanner.nextLine(); } } I am using this to parse an ~10MB text file. The problem is, if I put a breakpoint on the while() and the scanner.nextLine(), I can see that sometimes the scanners position (in the debug window) goes back to zero. I think this is causing me some kind of loop blow up, because the regext in findInLine() starts at zero, looks through some amount of text, advancing the position, and then it randomly gets set back to zero, so it has to re-parse all that text again. Any ideas what can be causing that? Am I even doing this the right way? Thanks Some additional info: The Scanner is instantiated from an InputStream. After diubg sine debugging, it appears that there is a HearCharBuffer that Scanner uses and it only allows 1024 characters at a time, and then resets. Is there a way to avoid this, or do things differently? That seems like a small amount of characters to be able to scan. Derek

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  • JPA in distributed Java EE configuration

    - by sof
    Hello, I'm developing a JEE application to run on Glassfish: Database (javaDB, MS SQL, MySQL or Oracle) EJB layer with JPA (Toplink essentials - from Glassfish) for database access JSF/Icefaces based web UI accessing the EJB layer The application will have a lot of concurrent web client, so I want to run it on different physical servers and use a load-balancer. My problem is now how to keep the applications synchronized. I intend to set up multiple servers, each running Glassfish with my EAR app installed. Whenever on one of the servers data is added to or removed from the database (via JPA, no direct SQL queries), this change should be reflected in the JPA layer on the other servers. I've been looking around for solutions to this, but couldn't find anything I really like (the full Toplink from Oracle claims to have a solution, but don't know). Doing a refresh before every access to a JPA entity could work, but is far from efficient. Are there any patterns, libraries, ... that could help here? Thanks a lot!

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  • Fastest way to learn Flex and Java EE?

    - by LostWebNewbie
    Ok so me and my 2 friends have to make a webapp and well we think it's a good opportunity to learn JEE and Flex. The thing is we have very little knowledge about them and we have only 3 months to do it (it doesn't have to be super complicated). So my question is: what, in your opinion, would be the fastest way to learn them both? I guess we need to know some JSP, Serlvets, JPA (??), Flex, maybe JavaScript+CSS? Anything else like EJB? Should we also learn Spring (or Struts)? Obviously reading books would be a good idea, but I bet we won't make the deadline if we try to read all the books... @Edit: I know the basics of JSP/Servlets (read Head First JSP&Servlets) but I made only 1 project so far (a semi-decent hangman with JSP/Serlvets and JPA for persistance) that's about it. Flex - I'm just starting, I know really the basics of mxml and as3. As for why: 1) because we need to do a project for the uni and well I was thinking bout becoming a web dev (yup - jee+flex) after graduation, this is the perfect opportunity to learn them.

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  • Recommendations for java captcha libraries

    - by skaffman
    I'm looking for a replacement for JCaptcha, which doesn't seem to be maintained any more, and isn't very good to begin with. The replacement has to integrate nicely with JavaEE webapps. As I can see it, there are three options: JCaptcha - No longer maintained, crude API SimpleCaptcha - much nicer API, nicer captchas, but seems to be Java6 only ReCaptcha - easy to use, uses remote web-service to generate captchas, but not much control over look and feel Has anyone used any others, that they'd recommend?

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  • Reading files with Java

    - by sikas
    I would like to know how can I read a file byte by byte then perform some operation every n bytes. for example: Say I have a file of size = 50 bytes, I want to divide it into blocks each of n bytes. Then each block is sent to a function for some operations to be done on those bytes. The blocks are to be created during the read process and sent to the function when the block reaches n bytes so that I don`t use much memory for storing all blocks. I want the output of the function to be written/appended on a new file. This is what I've reached to read, yet I don't know it it is right: fc = new JFileChooser(); File f = fc.getSelectedFile(); FileInputStream in = new FileInputStream(f); byte[] b = new byte[16]; in.read(b); I haven't done anything yet for the write process.

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  • How to crete a Java Iterator that throws IOException

    - by Antonio
    I'd like to implement an iterator that retrieves objects from disk/network. Iterator itr = getRemoteIterator(); while(itr.hasNext()) { Object element = itr.next(); System.out.print(element + " "); } However the problem is that hasNext() and next() methods of the Iterator object does not allow to throw IOException. Is there any other standard interface work around this issue? Desired code is: public interface RemoteIterator<E> { boolean hasNext() throws IOException; E next() throws IOException; void remove(); }

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  • Accessing Java Connector Architecture (JCA) from a Non-Managed environment

    - by Paul Kuykendall
    Hi, We have been using a JCA to interface with a low-level network resource from within WebSphere, however we have a requirement to be able to access the same network resource externally from Tomcat (i.e. not in a managed environment). The network communication and protocol layouts is very verbose, so we would rather not copy/paste several thousand lines of code (and then have to maintain them separately). From reading the JCA spec, there is supposedly some support to execute the code in a non-managed environment (such as Tomcat). Unfortunately, I have no idea what the interfaces are supposed to do, or how to call them from outside a managed environment (the spec is pretty vague). Are there any implementation examples out there that show how to modify a JCA to be usable in a non-managed environment? Thanks!

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  • Java Scanner - next String until a | is found

    - by user1375883
    Currently I'm trying to read through some basic cells, in this format: +-------+-------+ | | | +-------+-------+ Now I need to get the string representation of the cell's contents and send it off to another method. The problem is that the cells have no pre-defined length. I'm reading these from a file, so my easiest option should be to just use the Scanner I already have set up. Problem is, I don't really know how for this case. I have a strong feeling that I need to use the pattern somehow, but I'm at a complete loss on how to do it. I could also probably just build it up somehow, but that strikes me as being painfully slow.

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