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• download zip file using java?

  - by Mohamed

  I am downloading zip file from web server using Java but somehow I am loosing about 2kb in each file. I don't know why since same code works fine with other formats, e.g, text, mp3 and extra. any help is appreciated? here is my code. public void download_zip_file(String save_to) { try { URLConnection conn = this.url.openConnection(); conn.setDoOutput(true); conn.setDoInput(true); conn.setRequestProperty("content-type", "binary/data"); InputStream in = conn.getInputStream(); FileOutputStream out = new FileOutputStream(save_to + "tmp.zip"); byte[] b = new byte[1024]; int count; while ((count = in.read(b)) > 0) { out.write(b, 0, count); } out.close(); in.close(); } catch (IOException e) { e.printStackTrace(); } }

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• Create Personalized Controls For Java ME

  - by Nathan Campos

  I'm starting to develop a eBook reader for mobile using Java ME, but for the control were the book will be shown I need a personalized control. For this I need to first know how to do one, to workaround with my needs. Then I need to know how can I do a personalized control as we do with Visual Basic. PS: I want to do a personalized TextBox, that in some parts can be in bold, italic, sublined, that supports topics(as the Edit, the MS-DOS Text Editor) and many other things that make a eBook better viewed than a simple plain text

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• Java 2D clip area to shape

  - by user2923880

  I'm quite new to graphics in java and I'm trying to create a shape that clips to the bottom of another shape. Here is an example of what I'm trying to achieve: Where the white line at the base of the shape is the sort of clipped within the round edges. The current way I am doing this is like so: g2.setColor(gray); Shape shape = getShape(); //round rectangle g2.fill(shape); Rectangle rect = new Rectangle(shape.getBounds().x, shape.getBounds().y, width, height - 3); Area area = new Area(shape); area.subtract(new Area(rect)); g2.setColor(white); g2.fill(area); I'm still experimenting with the clip methods but I can't seem to get it right. Is this current method ok (performance wise, since the component repaints quite often) or is there a more efficient way? Thanks in advance.

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• Using a JSON web service from a Java client application

  - by user383341

  I am developing a client-side Java application that has a bit of functionality that requires getting data from some web services that transmit in JSON (some RESTful, some not). No JavaScript, no web browser, just a plain JAR file that will run locally with Swing for the GUI. This is not a new or unique problem; surely there must be some open source libraries out there that will handle the JSON data transmission over HTTP. I've already found some that will parse JSON, but I'm having trouble finding any that will handle the HTTP communication to consume the JSON web service. So far I've found Apache Axis2 apparently which might have at least part of the solution, but I don't see enough documentation for it to know if it will do what I need, or how to use it. Maybe part of the problem is that I don't have experience with web services so I'm not able to know a solution when I see it. I hope some of you can point me in the right direction. Examples would be helpful.

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• Retrieving Large Lists of Objects Using Java EE

  - by hallidave

  Is there a generally-accepted way to return a large list of objects using Java EE? For example, if you had a database ResultSet that had millions of objects how would you return those objects to a (remote) client application? Another example -- that is closer to what I'm actually doing -- would be to aggregate data from hundreds of sources, normalize it, and incrementally transfer it to a client system as a single "list". Since all the data cannot fit in memory, I was thinking that a combination of a stateful SessionBean and some sort of custom Iterator that called back to the server would do the trick. How have you successfully solved this problem in the past?

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• Java Hibernate/C3P0 error: "Could not obtain connection metadata. An attempt by a client to checkout

  - by Allan

  I'm trying to get some code I was passed up and running. It appears to use the Hibernate framework. I've gotten past most of the errors tweaking the configuration, but this one has me dead stumped. It's trying to connect to two databases: gameapp and gamelog. Both exist. It seems to have issues connecting to gamelog, but none connecting to gameapp (later in the init, it connects to and loads other DBs just fine). Below, I've pasted the error and exception stack dump. I imaging there's something else in the configs, so I've also included the configuration file for that db. I know this is very vague, but I'm hoping some pro can see the stupid mistake I'm missing. <?xml version="1.0" encoding="GBK"?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://127.0.0.1:3306/gamelog</property> <property name="connection.username">root</property> <property name="connection.password"></property> <property name="connection.useUnicode">true</property> <property name="connection.characterEncoding">UTF-8</property> <property name="hibernate.jdbc.batch_size">100</property> <property name="jdbc.fetch_size">1</property> <property name="hbm2ddl.auto">none</property><!-- update --> <property name="connection.useUnicode">true</property> <property name="show_sql">true</property> <!-- c3p0-configuration --> <property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property> <property name="hibernate.c3p0.min_size">5</property> <property name="hibernate.c3p0.max_size">10</property> <property name="hibernate.c3p0.timeout">30</property> <property name="hibernate.c3p0.idle_test_period">30</property> <property name="hibernate.c3p0.max_statements">0</property> <property name="hibernate.c3p0.acquire_increment">5</property> </session-factory> </hibernate-configuration> Exception and stack trace: 2010-04-30 17:50:00,411 WARN [org.hibernate.cfg.SettingsFactory] - Could not obtain connection metadata java.sql.SQLException: An attempt by a client to checkout a Connection has timed out. at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106) at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:65) at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:527) at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128) at org.hibernate.connection.C3P0ConnectionProvider.getConnection(C3P0ConnectionProvider.java:35) at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:76) at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:1933) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1216) at com.database.hibernate.util.HibernateFactory.<init>(Unknown Source) at com.database.hibernate.util.HibernateUtil.<clinit>(Unknown Source) at com.server.databaseop.goodOp.GoodOpImpl.initBreedGoods(Unknown Source) at com.server.databaseop.goodOp.GoodOpImpl.access$000(Unknown Source) at com.server.databaseop.goodOp.GoodOpImpl$1.run(Unknown Source) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351) at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:165) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:267) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:636) Caused by: com.mchange.v2.resourcepool.TimeoutException: A client timed out while waiting to acquire a resource from com.mchange.v2.resourcepool.BasicResourcePool@ca470 -- timeout at awaitAvailable() at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1317) at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557) at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477) at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525) ... 18 more

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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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• What's new in Servlet 3.1 ? - Java EE 7 moving forward

  - by arungupta

  Servlet 3.0 was released as part of Java EE 6 and made huge changes focused at ease-of-use. The idea was to leverage the latest language features such as annotations and generics and modernize how Servlets can be written. The web.xml was made as optional as possible. Servet 3.1 (JSR 340), scheduled to be part of Java EE 7, is an incremental release focusing on couple of key features and some clarifications in the specification. The main features of Servlet 3.1 are explained below: Non-blocking I/O - Servlet 3.0 allowed asynchronous request processing but only traditional I/O was permitted. This can restrict scalability of your applications. Non-blocking I/O allow to build scalable applications. TOTD #188 provide more details about how non-blocking I/O can be done using Servlet 3.1. HTTP protocol upgrade mechanism - Section 14.42 in the HTTP 1.1 specification (RFC 2616) defines an upgrade mechanism that allows to transition from HTTP 1.1 to some other, incompatible protocol. The capabilities and nature of the application-layer communication after the protocol change is entirely dependent upon the new protocol chosen. After an upgrade is negotiated between the client and the server, the subsequent requests use the new chosen protocol for message exchanges. A typical example is how WebSocket protocol is upgraded from HTTP as described in Opening Handshake section of RFC 6455. The decision to upgrade is made in Servlet.service method. This is achieved by adding a new method: HttpServletRequest.upgrade and two new interfaces: javax.servlet.http.HttpUpgradeHandler and javax.servlet.http.WebConnection. TyrusHttpUpgradeHandler shows how WebSocket protocol upgrade is done in Tyrus (Reference Implementation for Java API for WebSocket). Security enhancements Applying run-as security roles to #init and #destroy methods Session fixation attack by adding HttpServletRequest.changeSessionId and a new interface HttpSessionIdListener. You can listen for any session id changes using these methods. Default security semantic for non-specified HTTP method in <security-constraint> Clarifying the semantics if a parameter is specified in the URI and payload Miscellaneous ServletResponse.reset clears any data that exists in the buffer as well as the status code, headers. In addition, Servlet 3.1 will also clears the state of calling getServletOutputStream or getWriter. ServletResponse.setCharacterEncoding: Sets the character encoding (MIME charset) of the response being sent to the client, for example, to UTF-8. Relative protocol URL can be specified in HttpServletResponse.sendRedirect. This will allow a URL to be specified without a scheme. That means instead of specifying "http://anotherhost.com/foo/bar.jsp" as a redirect address, "//anotherhost.com/foo/bar.jsp" can be specified. In this case the scheme of the corresponding request will be used. Clarification in HttpServletRequest.getPart and .getParts without multipart configuration. Clarification that ServletContainerInitializer is independent of metadata-complete and is instantiated per web application. A complete replay of What's New in Servlet 3.1: An Overview from JavaOne 2012 can be seen here (click on CON6793_mp4_6793_001 in Media). Each feature will be added to the JSR subject to EG approval. You can share your feedback to users@servlet-spec.java.net. Here are some more references for you: Servlet 3.1 Public Review Candidate Downloads Servlet 3.1 PR Candidate Spec Servlet 3.1 PR Candidate Javadocs Servlet Specification Project JSR Expert Group Discussion Archive Java EE 7 Specification Status Several features have already been integrated in GlassFish 4 Promoted Builds. Have you tried any of them ? Here are some other Java EE 7 primers published so far: Concurrency Utilities for Java EE (JSR 236) Collaborative Whiteboard using WebSocket in GlassFish 4 (TOTD #189) Non-blocking I/O using Servlet 3.1 (TOTD #188) What's New in EJB 3.2 ? JPA 2.1 Schema Generation (TOTD #187) WebSocket Applications using Java (JSR 356) Jersey 2 in GlassFish 4 (TOTD #182) WebSocket and Java EE 7 (TOTD #181) Java API for JSON Processing (JSR 353) JMS 2.0 Early Draft (JSR 343) And of course, more on their way! Do you want to see any particular one first ?

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• Handling file upload in a non-blocking manner

  - by Kaliyug Antagonist

  The background thread is here Just to make objective clear - the user will upload a large file and must be redirected immediately to another page for proceeding different operations. But the file being large, will take time to be read from the controller's InputStream. So I unwillingly decided to fork a new Thread to handle this I/O. The code is as follows : The controller servlet /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse * response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub System.out.println("In Controller.doPost(...)"); TempModel tempModel = new TempModel(); tempModel.uploadSegYFile(request, response); System.out.println("Forwarding to Accepted.jsp"); /*try { Thread.sleep(1000 * 60); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); }*/ request.getRequestDispatcher("/jsp/Accepted.jsp").forward(request, response); } The model class package com.model; import java.io.IOException; import java.util.concurrent.ExecutionException; import java.util.concurrent.Future; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.utils.ProcessUtils; public class TempModel { public void uploadSegYFile(HttpServletRequest request, HttpServletResponse response) { // TODO Auto-generated method stub System.out.println("In TempModel.uploadSegYFile(...)"); /* * Trigger the upload/processing code in a thread, return immediately * and notify when the thread completes */ try { FileUploaderRunnable fileUploadRunnable = new FileUploaderRunnable( request.getInputStream()); /* * Future<FileUploaderRunnable> future = ProcessUtils.submitTask( * fileUploadRunnable, fileUploadRunnable); * * FileUploaderRunnable processed = future.get(); * * System.out.println("Is file uploaded : " + * processed.isFileUploaded()); */ Thread uploadThread = new Thread(fileUploadRunnable); uploadThread.start(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } /* * catch (InterruptedException e) { // TODO Auto-generated catch block * e.printStackTrace(); } catch (ExecutionException e) { // TODO * Auto-generated catch block e.printStackTrace(); } */ System.out.println("Returning from TempModel.uploadSegYFile(...)"); } } The Runnable package com.model; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.nio.ByteBuffer; import java.nio.channels.Channels; import java.nio.channels.ReadableByteChannel; public class FileUploaderRunnable implements Runnable { private boolean isFileUploaded = false; private InputStream inputStream = null; public FileUploaderRunnable(InputStream inputStream) { // TODO Auto-generated constructor stub this.inputStream = inputStream; } public void run() { // TODO Auto-generated method stub /* Read from InputStream. If success, set isFileUploaded = true */ System.out.println("Starting upload in a thread"); File outputFile = new File("D:/06c01_output.seg");/* * This will be changed * later */ FileOutputStream fos; ReadableByteChannel readable = Channels.newChannel(inputStream); ByteBuffer buffer = ByteBuffer.allocate(1000000); try { fos = new FileOutputStream(outputFile); while (readable.read(buffer) != -1) { fos.write(buffer.array()); buffer.clear(); } fos.flush(); fos.close(); readable.close(); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println("File upload thread completed"); } public boolean isFileUploaded() { return isFileUploaded; } } My queries/doubts : Spawning threads manually from the Servlet makes sense to me logically but scares me coding wise - the container isn't aware of these threads after all(I think so!) The current code is giving an Exception which is quite obvious - the stream is inaccessible as the doPost(...) method returns before the run() method completes : In Controller.doPost(...) In TempModel.uploadSegYFile(...) Returning from TempModel.uploadSegYFile(...) Forwarding to Accepted.jsp Starting upload in a thread Exception in thread "Thread-4" java.lang.NullPointerException at org.apache.coyote.http11.InternalInputBuffer.fill(InternalInputBuffer.java:512) at org.apache.coyote.http11.InternalInputBuffer.fill(InternalInputBuffer.java:497) at org.apache.coyote.http11.InternalInputBuffer$InputStreamInputBuffer.doRead(InternalInputBuffer.java:559) at org.apache.coyote.http11.AbstractInputBuffer.doRead(AbstractInputBuffer.java:324) at org.apache.coyote.Request.doRead(Request.java:422) at org.apache.catalina.connector.InputBuffer.realReadBytes(InputBuffer.java:287) at org.apache.tomcat.util.buf.ByteChunk.substract(ByteChunk.java:407) at org.apache.catalina.connector.InputBuffer.read(InputBuffer.java:310) at org.apache.catalina.connector.CoyoteInputStream.read(CoyoteInputStream.java:202) at java.nio.channels.Channels$ReadableByteChannelImpl.read(Unknown Source) at com.model.FileUploaderRunnable.run(FileUploaderRunnable.java:39) at java.lang.Thread.run(Unknown Source) Keeping in mind the point 1., does the use of Executor framework help me in anyway ? package com.utils; import java.util.concurrent.Future; import java.util.concurrent.ScheduledThreadPoolExecutor; public final class ProcessUtils { /* Ensure that no more than 2 uploads,processing req. are allowed */ private static final ScheduledThreadPoolExecutor threadPoolExec = new ScheduledThreadPoolExecutor( 2); public static <T> Future<T> submitTask(Runnable task, T result) { return threadPoolExec.submit(task, result); } } So how should I ensure that the user doesn't block and the stream remains accessible so that the (uploaded)file can be read from it?

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• Simple Java networking game engine [on hold]

  - by Florian Peschka

  I want to create a simple java networking game and search a networking engine that eases use of sockets etc. I have already read some questions on here and the internet about java networking for games, but many of them were over 10 years old or not really answered. I have no idea whatsoever about what exactly I need to send in terms of messages, but I figured simple strings or integers will be enough for my purposes. It's basically a peer to peer game, so I don't need a centralized server structure. Messaging doesn't have to have an extremely low ping, yet of course all players need to have a synchronized view. What are the possibilities I have here?

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• Open source Java CMS for Google App Engine?

  - by markvgti

  I am looking for an open source Java CMS (Web CMS, actually) to run on Google App Engine. I have looked at related older questions on this topic (What CMS runs on Google AppEngine?, CMS over Google App Engine, with SEO etc.) but the problem is that they all largely list Python-based CMSes. Plus these questions are pretty old, and since GAE is a fast-moving target, I thought it might be worthwhile to ask again. I want a CMS for creating some websites (for myself and for others), but would rather not start writing one from scratch. A "good" (very subjective, I know) open source WCMS allows me to start using a product, while still being able to add to/extend the product/project. On the one hand I am looking for a somewhat mature product/project, on the other hand it's easier to start contributing to the development cycle of a young product/project (conflicting, I know :-). Here are some features that would be preferable: [X]HTML/XML/CSS based templating Ability to create multiple blogs Galleries Ability to create a "Downloads" section (is this pretty much standard?) Separate management for digital assets (images, PDFs, binary files etc.) Roles like "Administrator", "Editor", "Contributor" etc. (or their equivalents) Ability to move/reorganize pages Export to PDF Reformat content for printing Is the CMS you are about to suggest especially well-suited to publishing an online book? My idea is that while the book may be offered as a downloadable eBook, the latest, most current version will be the one available on the website.

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• Java Spotlight Episode 84: Anil Gaur on JavaEE 7

  - by Roger Brinkley

  Tweet Interview with Anil Gaur, VP of Java Platform for Enterprise Edition and GlassFish Server, on JavaEE 7. Joining us this week on the Java All Star Developer Panel are Dalibor Topic, Java Free and Open Source Software Ambassador and Arun Gupta, Java EE Guy. Right-click or Control-click to download this MP3 file. You can also subscribe to the Java Spotlight Podcast Feed to get the latest podcast automatically. If you use iTunes you can open iTunes and subscribe with this link:  Java Spotlight Podcast in iTunes. Show Notes News Tori Wieldt - Judges Selected for Duke's Choice Awards Donald Smith - #OpenJDK interview in Java Magazine Henrik Ståhl - Java 7 adoption at 23% JavaOne Kicks Off with Sunday Keynotes at Masonic Auditorium Jersey 2.0 M4 JSF 2.2 Latest Snapshot NetBeans IDE 7.2 - Deploy to Cloud Events May 30, OTN Java Developer Day, Redwood Shores June 11-14, Cloud Computing Expo, New York City June 12, Boulder JUG June 13, Denver JUG June 13, Eclipse Juno DemoCamp, Redwoood Shore June 13, JUG Münster June 14, Java Klassentreffen, Vienna, Austria June 18-20, QCon, New York City June 26-28, Jazoon, Zurich, Switzerland July 5, Java Forum, Stuttgart, Germany July 30-August 1, JVM Language Summit, Santa Clara Feature InterviewAnil Gaur is the Vice President of Java Platform, Enterprise Edition, and GlassFish Server at Oracle in the Fusion Middleware Group. Is responsible for creation of Java EE Specifications, Reference Implementation, and Compatibility Test Suites. Leading the evolution on Java EE into Cloud and PaaS environment through the Java EE 7 standard. Prior to that, managed the delivery of Java EE 6 Platform and SDK which quickly gained momentum in enterprise application development and deployments. In this episode we talk about GlassFish 3.1 release. Mail Bag What’s Cool RFR (L): Adding core file parsing on Mac OS X to SA Sergio Del Valle @swdelvalle is the 1,000 @JavaSpotlight twitter follower

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• Tech Article: Powerful Logging in Java ME

  - by OracleTechnologyNetwork

  Learn how to add logging to your Java ME MIDlets with Microlog, an open-source logging library.

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• java.lang.ClassCastException: $Proxy99 cannot be cast

  - by svaret

  Hi, I am using JBoss4.2.2 and java6. The deployed ear's name is apa.ear In a servlet I have the following code line: placeBid = (PlaceBid) context.lookup("apa/" + PlaceBid.class.getSimpleName() + "/remote"); I have a generated jboss-app.xml like this: <jboss-app> <loader-repository>apa:app=ejb3</loader-repository> </jboss-app> When trying to get the PlaceBid via the context I get this exception java.lang.ClassCastException: $Proxy99 cannot be cast to se.nextit.actionbazaar.buslogic.PlaceBid The PlaceBid interface looks like this: @Remote public interface PlaceBid { Long addBid(String userId, Long itemId, Double bidPrice); } When I run the example coming with EJB3 in action it works. EJB3 in action sample code comes with ant building. I want to use Maven so I have rearranged the code some. However, I don't understan what I am doing wrong here. I have some thoughts about the jboss-app.xml file. I am not sure of how its content should look like. Grateful for any help. Best wishes Lasse

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• Java Transaction Service without the application server

  - by johnny

  Is it possible to have a Java standalone application (no application server attached) that exposes some operations that a client can call and be the one to manage the transactions? I was thinking this application to expose JNDI resources and get a hold of a java:comp/UserTransaction from there, get also a bean from there and call methods A, B and C on it and coordinate the transaction from the client? The application I'm writing isn't complex enough so that I need a big application server around it so I'm thinking to have a standalone JTS inside it that the client could interact with from a transactions point of view. I don't have much experience with distributed transactions and don't really know how to tackle the issue. Is it even possible? Am I getting myself into something beyond what a mere mortal (programmer) can handle? How can I approach this?

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• ca-certificates-java fails to install

  - by Jonas

  I use a VPS with Ubuntu Server 10.10. I want to use Jetty and run the command sudo apt-get install jetty but it fails because the installation encounted errors while processing ca-certificates-java. I have tried to install the failed package with: sudo apt-get install ca-certificates-java How can I solve this? I have run sudo apt-get update and sudo apt-get upgrade but I get the same errors after that. I have also installed Ubuntu Server x64 on a VirtualBox, but the two Ubuntu Server 10.10 has different kernel versions (2.6.35 on VirtualBox and 2.6.18 on my VPS). And on VirtualBox I can install Jetty without any problems.

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• Feasibility to take over a JavaMe Project by Coders who have no experience in JavaMe

  - by Stephenmjm

  As the original JavaMe team will leave to do other items. The JavaMe project will be taken over by some guys knowing nothing about JavaMe. Transition period: One month About this JavaMe project: about 3.5 million lines of code (more than 180 java file, SourceCode is 8.5KB in total) using the Polish, Proguard document: The JavaMe project itself have no document. No UML map. Difficulties I guess: familiar with the JavaMe, this should be okay In order to do the further development. We need to Read the sourceCode ---- It's not easy to read 3.5 million lines of code having not enough comment Adaptation work for more than 100 phone These are the questions, thank you! In the case of our guys have no experience in JavaMe, Is one month too hasty? In order to take the job in time . What we should ask the original JavaMe team to do . Considering we hava no experience in JavaMe. The complication we taking the Adaptation work without the original JavaMe team? Any other suggestions?

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• Eloqua API Full Code Example in JAVA

  - by Shawn Spencer

  Is there anyone out there who has mastered to retrieve some data programmatically from Eloqua? First of all, I'm more or less a newbie, as far as JAVA. I can follow tutorials, take directions and will Google till my fingers bleed. I understand the basics and am slightly familiar with OOP. My main problem is that I have a Friday deadline (and tomorrow is Thanksgiving). At any rate, all the Eloqua code snippets (that I've been able to find) illustrate one aspect of a specific issue, and that's it. In my case, I would greatly appreciate a JAVA project of some sort, with all the necessary files to do web services (WSDL, SOAP and perhaps WSIT) and the main class and all that included. No, I don't want you to do my work for me! Just give me enough to find my way around, enter the information I need to retrieve and all that. I'll take it from there. Any pointers, links or suggestions?

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• Java ExecutorService java heap space ptoblems

  - by Sergey Aganezov jr

  I have a little bit of a problem in a multitasking java department. I have a class, called public class ThreadWorker implements Runnable { //some code in here public void run(){ // invokes some recursion method in the ThreadWorker itself, // which will stop eventually { } all in all, pretty simple "worker" that can work on it's on. To work with threads I'm using public static int THREAD_NUMBER = 4; public static ExecutorServide es = Executors.newFixedThreadPool(THREAD_NUMBER); adding instances of ThreadWroker class happens here: public void recursiveMethod(Arraylist<Integers> elements, MyClass data){ if (elements.size() == 0 && data.qualifies()){ ThreadWorker tw = new ThreadWorker(data); es.execute(tw); return; } for (int i=0; i< elements.size(); i++){ // some code to prevent my problem MyClass data1 = new MyClass(data); MyClass data2 = new MyClass(data); ArrayList<Integer> newElements = (ArrayList<Integer>)elements.clone(); data1.update(elements.get(i)); data2.update(-1 * elements.get(i)); newElements.remove(i); recursiveMethod(newElements, data1); recursiveMethod(newElements, data2); { } and the problem is that the depth of the recursion tree is quite big, so as it's width, so a lot of ThreadWorkers are added to the ExecutorService, so after some time on the big input a get Exception in thread "pool-1-thread-2" java.lang.OutOfMemoryError: Java heap space which is caused, as I think because of a ginormous number of ThreadWorkers i'm adding to ExecutorSirvice to be executed, so it runs out of memory. Every ThreadWorker takes about 40 Mb of RAM for all it needs. Is there a method to get how many threads (instances of classes implementing runnable interface) have been added to ExecutorService? So I can add it in the shown above code (int the " // some code to prevent my problem"), as while ("number of threads in the ExecutorService" > 10){ Thread.sleep(10000); } so I won't go to deep or to broad with my recursion and prevent those exception-throwing situations. Sincerely, Sergey Aganezov jr.

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• Question about casting a class in Java with generics

  - by Florian F

  In Java 6 Class<? extends ArrayList<?>> a = ArrayList.class; gives and error, but Class<? extends ArrayList<?>> b = (Class<? extends ArrayList<?>>)ArrayList.class; gives a warning. Why is (a) an error? What is it, that Java needs to do in the assignment, if not the cast shown in (b)? And why isn't ArrayList compatible with ArrayList? I know one is "raw" and the other is "generic", but what is it you can do with an ArrayList and not with an ArrayList, or the other way around?

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• Talking JavaOne with Rock Star Raghavan Srinivas

  - by Janice J. Heiss

  Raghavan Srinivas, affectionately known as “Rags,” is a two-time JavaOne Rock Star (from 2005 and 2011) who, as a Developer Advocate at Couchbase, gets his hands dirty with emerging technology directions and trends. His general focus is on distributed systems, with a specialization in cloud computing. He worked on Hadoop and HBase during its early stages, has spoken at conferences world-wide on a variety of technical topics, conducted and organized Hands-on Labs and taught graduate classes.He has 20 years of hands-on software development and over 10 years of architecture and technology evangelism experience and has worked for Digital Equipment Corporation, Sun Microsystems, Intuit and Accenture. He has evangelized and influenced the architecture of numerous technologies including the early releases of JavaFX, Java, Java EE, Java and XML, Java ME, AJAX and Web 2.0, and Java Security.Rags will be giving these sessions at JavaOne 2012: CON3570 -- Autosharding Enterprise to Social Gaming Applications with NoSQL and Couchbase CON3257 -- Script Bowl 2012: The Battle of the JVM-Based Languages (with Guillaume Laforge, Aaron Bedra, Dick Wall, and Dr Nic Williams) Rags emphasized the importance of the Cloud: “The Cloud and the Big Data are popular technologies not merely because they are trendy, but, largely due to the fact that it's possible to do massive data mining and use that information for business advantage,” he explained. I asked him what we should know about Hadoop. “Hadoop,” he remarked, “is mainly about using commodity hardware and achieving unprecedented scalability. At the heart of all this is the Java Virtual Machine which is running on each of these nodes. The vision of taking the processing to where the data resides is made possible by Java and Hadoop.” And the most exciting thing happening in the world of Java today? “I read recently that Java projects on github.com are just off the charts when compared to other projects. It's exciting to realize the robust growth of Java and the degree of collaboration amongst Java programmers.” He encourages Java developers to take advantage of Java 7 for Mac OS X which is now available for download. At the same time, he also encourages us to read the caveats. Originally published on blogs.oracle.com/javaone.

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• Java: volatile guarantees and out-of-order execution

  - by WizardOfOdds

  Note that this question is solely about the volatile keyword and the volatile guarantees: it is not about the synchronized keyword (so please don't answer "you must use synchronize" for I don't have any issue to solve: I simply want to understand the volatile guarantees (or lack of guarantees) regarding out-of-order execution). Say we have an object containing two volatile String references that are initialized to null by the constructor and that we have only one way to modify the two String: by calling setBoth(...) and that we can only set their references afterwards to non-null reference (only the constructor is allowed to set them to null). For example (it's just an example, there's no question yet): public class SO { private volatile String a; private volatile String b; public SO() { a = null; b = null; } public void setBoth( @NotNull final String one, @NotNull final String two ) { a = one; b = two; } public String getA() { return a; } public String getB() { return b; } } In setBoth(...), the line assigning the non-null parameter "a" appears before the line assigning the non-null parameter "b". Then if I do this (once again, there's no question, the question is coming next): if ( so.getB() != null ) { System.out.println( so.getA().length ); } Am I correct in my understanding that due to out-of-order execution I can get a NullPointerException? In other words: there's no guarantee that because I read a non-null "b" I'll read a non-null "a"? Because due to out-of-order (multi)processor and the way volatile works "b" could be assigned before "a"? volatile guarantees that reads subsequent to a write shall always see the last written value, but here there's an out-of-order "issue" right? (once again, the "issue" is made on purpose to try to understand the semantics of the volatile keyword and the Java Memory Model, not to solve a problem).

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• Java Cryptography Extension

  - by Adam Tannon

  I was told that in order to support AES256 encryption inside my Java app that I would need the JCE with Unlimited Strength Jurisdiction Policy Files. I downloaded this from Oracle and unzipped it and I'm only seeing 2 JARs: local_policy.jar; and US_export_polic.jar I just want to confirm I'm not missing anything here! My understanding (after reading the README.txt) is that I just drop these two into my <JAVA_HOME>/lib/security/ directory and they should be installed. By the names of these JARs I have to assume that its not the Java Crypto API that cannot handle AES256, but it's in fact a legal issue, perhaps? And that these two JARs basically tell the JRE "yes, it's legally-acceptable to run this level of crypto (AES256)." Am I correct or off-base?

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• Resources for game networking in Java

  - by pudelhund

  I am currently working on a Java multiplayer game. The game itself (single player) already works perfectly fine and so does the chat. The only thing that is really missing is the multiplayer part. Sadly I am absolutely clueless on where to start with that. I roughly know that I will have to work with packages, and I also know many things about streaming etc (chat is already working). Oh and it should - according to this article - be a UDP server. My problem is that I can't find any resources on how to do this. A tutorial (book or website) would be perfect, alternatively a good example of an open source client/server (in Java of course) would be fine as well. If you feel like doing something helpful I'd also really appreciate someone "privately" teaching me via email or some chat program :) Thank you!

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• Can't decide between Java or Python for college [on hold]

  - by Will Harrison

  I'm returning to college in about a month for Computer Science. My problem is, I have been programming on the web since I left (4 years ago), using PHP, ASP.NET, and JavaScript. I want to bone up on a more general purpose language that is cross platform before I begin. I would also like to be using a language that is common at my school and I know that they teach the students C++, Java, and Python. I would like to choose between Java or Python but I'm not sure which one. What do you think would be better based on job prospects in the next 2 years and community?

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