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  • Switching from Java to .NET from a career change point of view

    - by Joe
    Could anyone share with me their experience with switching from Java to .NET from a career point of view? I've been a Java developer for 12 years and am just getting tired of how fragmented the Java world has become. For my liking, there's just too many frameworks, tools, application servers, etc.. And it seems each new tool just adds complexity and time to even the simplest of projects. I'm not trying to start any wars - I'm just giving you the reason I ask the main question. I've read a few books on .NET and have done one WebForms job. I love the integrated environment and would like to hear how others transitioned from Java to .NET. What I mean by that is did you do it somehow as a contractor or did you join a company as a beginner .NET developer with much Java experience? Personally, I'm ready to take the leap if I can figure out how to not lose too much income in the process (Senior Java developer to beginner .NET developer). I would really appreciate hearing your stories.

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  • java serialization problems with different JVMs

    - by Alberto
    I am having trouble using serialization in Java. I've searched the web for a solution but haven't found an answer yet. The problem is this - I have a Java library (I have the code and I export it to an archive prior to executing the code) which I need to use with two differents JVMs. One JVM is on the server (Ubuntu, running Java(TM) JRE SE Runtime Environment (build 1.7.0_09-b05)) and the other on Android 2.3.3. I compiled the library in Java 1.6. Now, I am trying to import to the client, an object exported from the server, but I receive this error: java.io.InvalidClassException: [Lweka.classifiers.functions.MultilayerPerceptron$NeuralEnd;; Incompatible class (SUID): [Lweka.classifiers.functions.MultilayerPerceptron$NeuralEnd;: static final long serialVersionUID =-359311387972759020L; but expected [Lweka.classifiers.functions.MultilayerPerceptron$NeuralEnd;: static final long serialVersionUID =1920571045915494592L; I do have an explicit serial version UID declared on the class MultilayerPerceptron$NeuralEnd, like this: protected class NeuralEnd extends NeuralConnection { private static final long serialVersionUID = 7305185603191183338L; } Where NeuralConnection implements the java.io.Serializable interface. If I do a serialver on MultilayerPerceptron$NeuralEnd I receive the serialVersionUID which I declared. So, why have both JVMs changed this value? Can you help me? Thanks, Alberto

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  • How do I make "simple" throughput servlet-filter?

    - by Tommy
    I'm looking to create a filter that can give me two things: number of request pr minute, and average responsetime pr minute. I already got the individual readings, I'm just not sure how to add them up. My filter captures every request, and it records the time each request takes: public void doFilter(ServletRequest request, ...() { long start = System.currentTimeMillis(); chain.doFilter(request, response); long stop = System.currentTimeMillis(); String time = Util.getTimeDifferenceInSec(start, stop); } This information will be used to create some pretty Google Chart charts. I don't want to store the data in any database. Just a way to get current numbers out when requested As this is a high volume application; low overhead is essential. I'm assuming my applicationserver doesn't provide this information.

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  • Logging exceptions during bean injection

    - by Marc W
    I think this is a pretty basic question, but after Googling around I can't seem to find the answer. What I need is a way to log some custom output with log4j during Spring bean construction. I have a factory class called ResponderFactory (being used as an instance factory in Spring) with a factory method that can throw 2 different types of exception. public CollectorResponder collectorResponder(String inputQueueName) throws ConfigurationException, BrokerConnectionException {} Now, normally I could wrap a call to this method in a try-catch block with 2 catch clauses to handle the logging situations for each of the exceptions. However, if I'm using Spring to inject this CollectorResponder, created with the factory, into another class I don't see how this is possible. <bean id="responderFactory" class="com.package.ResponderFactory"> <constructor-arg index="0" ref="basicDispatcher" /> <constructor-arg index="1" value="http://localhost:9000" /> </bean> <bean id="collectorResponder" class="com.package.CollectorResponder" factory-bean="responderFactory" factory-method="collectorResponder"> <constructor-arg value="collector.in" /> </bean> <bean id="collectorConsumer" class="com.package.CollectorConsumer"> <constructor-arg ref="collectorResponder" /> </bean> Again, I want to catch these exceptions when the collectorResponder bean is instantiated. Right now I'm dealing with this is CollectorConsumer when I instantiate using new CollectorResponder(...). Is there any way I can do this?

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  • Is JAX-RS suitable as a MVC framework?

    - by deamon
    JAX-RS has some MVC support, but I wonder if JAX-RS is really a good choice to build web application for human use. If a user enters wrong or incomplete information in a form, it should be displayed again like with Grails or Wicket. Is there a comfortable way to do this with JAX-RS? As far as I know the URI mapping doesn't work correctly, if not all required parameters are given or there are type conversion problems (with Date for example). Is that correct? Is there support for internationalized templates?

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  • Do servlet containers prevent web applications from causing each other interference and how do they do it?

    - by chrisbunney
    I know that a servlet container, such as Apache Tomcat, runs in a single instance of the JVM, which means all of its servlets will run in the same process. I also know that the architecture of the servlet container means each web application exists in its own context, which suggests it is isolated from other web applications. As depicted here: Accepting that each web application is isolated, I would expect that you could create 2 copies of an identical web application, change the names and context paths of each (as well as any other relevant configuration), and run them in parallel without one affecting the other. The answers to this question appear to support this view. However, a colleague disagrees based on their experience of attempting just that. They took a web application and tried to run 2 separate instances (with different names etc) in the same servlet container and experienced issues with the 2 instances conflicting (I'm unable to elaborate more as I wasn't involved in that work). Based on this, they argue that since the web applications run in the same process space, they can't be isolated and things such as class attributes would end up being inadvertently shared. This answer appears to suggest the same thing The two views don't seem to be compatible, so I ask you: Do servlet containers prevent web applications deployed to the same container from conflicting with each other? If yes, How do they do this? If no, Why does interference occur? and finally, Under what circumstances could separate web applications conflict and cause each other interference?, perhaps scenarios involving resources on the file system, native code, or database connections?

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  • Servlet 3.0 logout doesn't work

    - by Kevin
    I've got a problem with the authentication features of Servlet 3.0: With this code in a Servlet v3: log.info(""+request.getUserPrincipal()); log.info(""+request.getAuthType()); log.info("===^==="); request.logout() ; log.info(""+request.getUserPrincipal()); log.info(""+request.getAuthType()); request.authenticate(response) ; log.info("===v==="); log.info(""+request.getUserPrincipal()); log.info(""+request.getAuthType()); I would always expect to see the Username/login windows, because of the logout() function. Instead, it seems to be a 'cache' mechanism which repopulate the credential and cancel my logout ... Admin BASIC ===^=== null null ===v=== Admin BASIC Is it a problem with my firefox, or something I'm missing in the Servlet code?

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  • Can I access Spring session-scoped beans from application-scoped beans? How?

    - by Corvus
    I'm trying to make this 2-player web game application using Spring MVC. I have session-scoped beans Player and application-scoped bean GameList, which creates and stores Game instances and passes them to Players. On player creates a game and gets its ID from GameList and other player sends ID to GameList and gets Game instance. The Game instance has its players as attributes. Problem is that each player sees only himself instead of the other one. Example of what each player sees: First player (Alice) creates a game: Creator: Alice, Joiner: Empty Second player (Bob) joins the game: Creator: Bob, Joiner: Bob First player refreshes her browser Creator: Alice, Joiner: Alice What I want them to see is Creator: Alice, Joiner: Bob. Easy way to achieve this is saving information about players instead of references to players, but the game object needs to call methods on its player objects, so this is not a solution. I think it's because of aop:scoped-proxy of session-scoped Player bean. If I understand this, the Game object has reference to proxy, which refers to Player object of current session. Can Game instance save/access the other Player objects somehow? beans in dispatcher-servlet.xml: <bean id="userDao" class="authorization.UserDaoFakeImpl" /> <bean id="gameList" class="model.GameList" /> <bean name="/init/*" class="controller.InitController" > <property name="gameList" ref="gameList" /> <property name="game" ref="game" /> <property name="player" ref="player" /> </bean> <bean id="game" class="model.GameContainer" scope="session"> <aop:scoped-proxy/> </bean> <bean id="player" class="beans.Player" scope="session"> <aop:scoped-proxy/> </bean> methods in controller.InitController private GameList gameList; private GameContainer game; private Player player; public ModelAndView create(HttpServletRequest request, HttpServletResponse response) throws Exception { game.setGame(gameList.create(player)); return new ModelAndView("redirect:game"); } public ModelAndView join(HttpServletRequest request, HttpServletResponse response, GameId gameId) throws Exception { game.setGame(gameList.join(player, gameId.getId())); return new ModelAndView("redirect:game"); } called methods in model.gameList public Game create(Player creator) { Integer code = generateCode(); Game game = new Game(creator, code); games.put(code, game); return game; } public Game join(Player joiner, Integer code) { Game game = games.get(code); if (game!=null) { game.setJoiner(joiner); } return game; }

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  • Managing resource closure in a servlet container

    - by Steven Schlansker
    I'm using Tomcat as a servlet container, and have many WARs deployed. Many of the WARs share common base classes, which are replicated in each context due to the different classloaders, etc. How can I ensure resource cleanup on context destruction, without hooking each and every web.xml file to add context listeners? Ideally, I'd like something along the lines of class MyResourceHolder implements SomeListenerInterface { private SomeResource resource; { SomeContextThingie.registerDestructionListener(this); } public void onDestroy() { resource.close(); } } I could put something in each web.xml, but since there are potentially many WARs and only ones that actually initialize the resource need to clean it up, it seems more natural to register for cleanup when the resource is initialized rather than duplicating a lot of XML configuration and then maybe cleaning up. (In this particular case, I'm initiating an orderly shutdown of a SQL connection pool. But I see this being useful in many other situations as well...) I'm sure there's some blisteringly obvious solution out there, but my Google-fu is failing me right now. Thanks!

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  • How to connect remote EJB module from application client

    - by Zeck
    Hi guys, I have a EJB module in remote Glassfish server and application client in my computer. I want to connect from the application client to the remote EJB. Here is the my EJB interface: @Remote public interface BookEJBRemote { public String getTitle(); } Here is the my ejb: @Stateless public class BookEJB implements BookEJBRemote { @Override public String getTitle() { return "Twenty Thousand Leagues Under the Sea"; } } I have several questions : Can I use Dependency Injection in the remote application client to connect to the ejb? If so what can i do to achieve this. Do i need to configure in the sun-ejb-jar.xml and sun-application-client.xml? In other words, if i use DI like @EJB MyEJBRemote ejb; How application client container know what ejb to be injected? Where should i specify the information? How can i run the application client? I tried to run package-appclient in the glassfish server to get appclient.jar and copy it to my computer. Then i type appclient.jar -client myAppClient.jar . It didn't work. How do i point the target server? if i cannot use DI in the client then i guess i have to use JNDI lookup. Do i need to configure jndi name in sun-ejb-jar.xml or in the sun-application-client.xml? No matter how i try i never manage to run application client ? Can you guys put some working example? And thank you for every advises and examples?

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  • Is 1/0 a legal Java expression?

    - by polygenelubricants
    The following compiles fine in my Eclipse: final int j = 1/0; // compiles fine!!! // throws ArithmeticException: / by zero at run-time Java prevents many "dumb code" from even compiling in the first place (e.g. "Five" instanceof Number doesn't compile!), so the fact this didn't even generate as much as a warning was very surprising to me. The intrigue deepens when you consider the fact that constant expressions are allowed to be optimized at compile time: public class Div0 { public static void main(String[] args) { final int i = 2+3; final int j = 1/0; final int k = 9/2; } } Compiled in Eclipse, the above snippet generates the following bytecode (javap -c Div0) Compiled from "Div0.java" public class Div0 extends java.lang.Object{ public Div0(); Code: 0: aload_0 1: invokespecial #8; //Method java/lang/Object."<init>":()V 4: return public static void main(java.lang.String[]); Code: 0: iconst_5 1: istore_1 // "i = 5;" 2: iconst_1 3: iconst_0 4: idiv 5: istore_2 // "j = 1/0;" 6: iconst_4 7: istore_3 // "k = 4;" 8: return } As you can see, the i and k assignments are optimized as compile-time constants, but the division by 0 (which must've been detectable at compile-time) is simply compiled as is. javac 1.6.0_17 behaves even more strangely, compiling silently but excising the assignments to i and k completely out of the bytecode (probably because it determined that they're not used anywhere) but leaving the 1/0 intact (since removing it would cause an entirely different program semantics). So the questions are: Is 1/0 actually a legal Java expression that should compile anytime anywhere? What does JLS say about it? If this is legal, is there a good reason for it? What good could this possibly serve?

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  • Some help required while working on Java and Cygwin together

    - by Hippo
    Hello .. I am new to java and also cygwin . I do not have in detailed knowledge of both . I need some help.. I simple steps i will try to explain my problem. 1) I am working on tinyOS . its open source OS , used for wireless sensor networks. It provides java libraries to work on communication (PC to sensor) 2) I am working on windows xp environment through cigwin. 3) I am developing an application . THis application requires one java interface called "Serial Forwarder" , which is readily available in libraries provided. Previously i used to start this interface manually (by entering command *"java net.tinyos.sf.SerialForwarder ")*and then my application which uses this interface. But now i want to make my application independent . User need know about this background cygwin commands . 4) So in my java application i used "Runtime.getRuntime().exec( "java net.tinyos.sf.SerialForwarder)" . 5) This i neither giving any error nor starting the interface. Am I going on right way ? When i am using runtime execute command , how can i make sure that this command is called through cigwin interface ? Also .. if i want to write .bat file .. i which i can give commands which will be executed .. how can i make sure that those commands are given through cigwin .. and not through cmd.exe .. Please help . me .

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  • Working with mongodb from Java

    - by demas
    I have launch mongodb server: [[email protected]][~]% mongod --dbpatmongod --dbpath /home/demas/temp/ Mon Apr 19 09:44:18 Mongo DB : starting : pid = 4538 port = 27017 dbpath = /home/demas/temp/ master = 0 slave = 0 32-bit ** NOTE: when using MongoDB 32 bit, you are limited to about 2 gigabytes of data ** see http://blog.mongodb.org/post/137788967/32-bit-limitations for more Mon Apr 19 09:44:18 db version v1.4.0, pdfile version 4.5 Mon Apr 19 09:44:18 git version: nogitversion Mon Apr 19 09:44:18 sys info: Linux arch.local.net 2.6.33-ARCH #1 SMP PREEMPT Mon Apr 5 05:57:38 UTC 2010 i686 BOOST_LIB_VERSION=1_41 Mon Apr 19 09:44:18 waiting for connections on port 27017 Mon Apr 19 09:44:18 web admin interface listening on port 28017 I have created documents by console client: [[email protected]][~]% mongo MongoDB shell version: 1.4.0 url: test connecting to: test type "help" for help > db.some.find(); { "_id" : ObjectId("4bcbef3c3be43e9b7e04ef3d"), "name" : "mongo" } { "_id" : ObjectId("4bcbef423be43e9b7e04ef3e"), "x" : 3 } Now I am trying to work with MongoDb from Java: import com.mongodb.*; import java.net.UnknownHostException; public class test1 { public static void main(String[] args) { System.out.println("Start"); try { Mongo m = new Mongo("localhost", 27017); DB db = m.getDB("test"); DBCollection coll = db.getCollection("some"); coll.insert(makeDocument(10, "James", "male")); System.out.println("Finish"); } catch (UnknownHostException ex) { ex.printStackTrace(); } catch (MongoException ex) { ex.printStackTrace(); } } public static BasicDBObject makeDocument(int id, String name, String gender) { BasicDBObject doc = new BasicDBObject(); doc.put("id", id); doc.put("name", name); doc.put("gender", gender); return doc; } } But execution stops on line coll.insert(): [[email protected]][~/dev/study/java/mongodb]% javac test1.java [[email protected]][~/dev/study/java/mongodb]% java test1 Start There are not messages from mogodb server regarding accepted connection. Why?

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  • How do I access Glassfish V3 Administration Console Website from a remote host

    - by Tom
    I have installed Glassfish v3 on a standalone server running ubuntu-server 9.10. I can open the Admin website if I use a browser running on the server by browsing to: http:// localhost:4848/ I would like to access it from a remote machine by browsing to something like http:// mydomain.com:4848/ The firewall is definitely allowing traffic through on that port (4848) and I can access the application server by browsing to: http:// mydomain.com:8080/ How can I allow remote access to the administration website?

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  • How does 'binding' in JSF work?

    - by Roman
    I've created custom component which shows chart. Now I need to make binding support for this component i.e. generated chart-image should be available (as array of bytes) to backing bean via binding mechanism. I'd like to know some general info about binding implementation techniques. Any links and examples are welcome as well. Thanks in advance!

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  • Correlation between JEE / J2EE to J2SE / JDK versions

    - by Ehrann Mehdan
    I was certain that I'll find a duplicate question or a satisfiyng answer, but I haven't. What I'm looking for is the answer to these questions: Is there an official correlation between JEE / J2EE and J2SE / JDK versions? If the answer is yes, where is it written? If the answer is no, then why? and is there an unofficial version table (e.g. JDK 1.4 goes well with J2EE 1.3, JDK 1.5 goes well with J2EE 1.4, JDK 1.6 with JEE 5 and so on) I can think of a couple of reasons for the uncoupling, but can't seem to find a good reference source Related questions: http://stackoverflow.com/questions/196265/jse-vs-j2ee-college-and-career/196439#196439 http://stackoverflow.com/questions/106820/what-is-j2ee-jee

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  • Calling Java classes from IzPack

    - by bguiz
    I am trying to write an IzPack installer which is able to detect a previously installed version of the application. After finding out that it doesn't really support this feature, I think the only way to do this is through writing a Java class and calling it from IzPack. Tim Williscroft has previously suggested this method: <condition type="java" id="jbossEnv"> <java> <class>au.com.codarra.ela.installer.JBossChecker</class <field>hasJBossEnv</field> </java> <returnvalue type="boolean">true</returnvalue> </condition> However, is it possible to call <java> from somewhere other than a <condition> tag? I want to be able to call it from a <variable> tag. Also, is it possible to call a method from a Java class instead of reading a value of a field? I want to be able to pass parameters to my class. Thank you!

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  • spring faces without spring flow

    - by AgostinoX
    I'm starting a new JSF (2) project. I realize that pure JSF has some limitation and I'm planning to drop in spring. JSF is a relatively new approach in spring (there is not even a tag spring-faces in stackoverflow :-) ), jsp being the classic way. I need the best available adjustment of the technology stack. 1) do i need to use spring web flow too? 2) is it viable to use just spring faces (that seems to come as a part of web flow) + spring mvc+ JPA? 3) is there any good example of such a configuration?

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  • Avoiding null point exception in el in JSF

    - by Buddhika Ariyaratne
    I am developing a JSF application with JPA(EclipseLink 2.0) and Primefaces. I want to know is there any way to avoid null point exception when el calls a property of a null object. I have described the situation. I have Bill class. There may be no or more BillItem objects with a Bill objects. Each BillItem object have Objects like Make, Country, Manufacturer, etc objects. I am displaying several properties of a bill within a single JSF file like this. "#{billControlled.bill.billItem.modal.name}" But if a bill is not selected, or when there are no bill items for a selected bill, the properties accessing in the el are null. I can avoid this by creating new objects for every bill, for example, new make for a new bill item, etc or by creating new properties in the controller itself for all the properties. But that is a very long way and feel like rudimentory. Is there any good practice to avoid this null point exception in el in JSF?

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  • Performance of Java matrix math libraries?

    - by dfrankow
    We are computing something whose runtime is bound by matrix operations. (Some details below if interested.) This experience prompted the following question: Do folk have experience with the performance of Java libraries for matrix math (e.g., multiply, inverse, etc.)? For example: JAMA: http://math.nist.gov/javanumerics/jama/ COLT: http://acs.lbl.gov/~hoschek/colt/ Apache commons math: http://commons.apache.org/math/ I searched and found nothing. Details of our speed comparison: We are using Intel FORTRAN (ifort (IFORT) 10.1 20070913). We have reimplemented it in Java (1.6) using Apache commons math 1.2 matrix ops, and it agrees to all of its digits of accuracy. (We have reasons for wanting it in Java.) (Java doubles, Fortran real*8). Fortran: 6 minutes, Java 33 minutes, same machine. jvisualm profiling shows much time spent in RealMatrixImpl.{getEntry,isValidCoordinate} (which appear to be gone in unreleased Apache commons math 2.0, but 2.0 is no faster). Fortran is using Atlas BLAS routines (dpotrf, etc.). Obviously this could depend on our code in each language, but we believe most of the time is in equivalent matrix operations. In several other computations that do not involve libraries, Java has not been much slower, and sometimes much faster.

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  • biginteger calucation prfoblem

    - by murali
    hi i am using the following code but the parameters are not passed to the methods. BigInteger p = BigInteger.valueOf(0); BigInteger u1 = obj.bigi_calc(g1, l); in this g1,l are long values the method is private BigInteger bigi_calc(long g1, long l){ BigInteger cal = BigInteger.valueOf(g1); BigInteger cal1= BigInteger.valueOf(l); for(BigInteger f = BigInteger.ONE;f.compareTo(cal1)>0;f=f.add(BigInteger.ONE)){ //BigInteger p= BigInteger.valueOf(0); p = cal.multiply(cal1); System.out.println("check p"+p); } // System.out.println("check p"+p); return p; } the elipse shows that it may be out of sync.. but the paramerters are not passed to the functions.. can you plz help me to slove this problem

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  • What's a good 2nd level cache for JEE applications?

    - by Hank
    Can anyone recommend a good 2nd level object caching solution for JEE 6 applications, and give background to your recommendation? I'm using JPA 2.0 as persistence provider. I am particularly worried about having to run the cache client as a single-thread / singleton bean. Is that the case? If so, is that an issue? I've good experience using memcached from a PHP webapp, but PHP is of course single-threaded, so that was never an issue...

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  • Best practices for caching results of JSP pages?

    - by Spines
    My application has an MVC structure. How should I structure my application to allow for maximum caching? Is it sufficient to only cache the model objects that are passed to the JSP views? Or will there be a significant performance boost from caching the results of the rendering of the JSP views too?

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