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• Maximum number of type parameters used in a java class

  - by True Soft

  What is the maximum number of type parameters you used in a java class? Example for 4: class MyClass<A, B, C, D> { }

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• Java. Best procedure to de-serialize a Java generic object?

  - by Jake

  What is the best procedure for storing and retrieving, using native Java serialization, generic objects like ArrayList<String>? Edit: To clarify. When I serialize an object of type ArrayList<String> I'd like to de-serialize to the same type of object. However, I know of no way to cast back to this generic object without causing warnings.

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• C++Template in Java?

  - by RnMss

  I want something like this: public abstract class ListenerEx<LISTENER, PARENT> implements LISTENER { PARENT parent; public ListenerEx(PARENT p) { parent = p; } } But it doesn't compile. Is there a better solution? Is there something in Java like C++ template that would do check syntax after template deduction? The following explains why I need such a ListenerEX class, if you already know what it is, you don't need to read the following. I have a main window, and a button on it, and I want to get access to some method of the main window's within the listener: public class MainWindow extends JFrame { public void doSomething() { /* ... */ } public void doSomethingElse() { /* ... */ } private JButton button; public MainWindow() { button = new JButton(...); add(button); button.setActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { doSomething(); doSomethingElse(); } }); } } This would compile but does not work properly all the time. (Why would it compile when the ActionListener does not have doSomething() method?) Of course we can do it like this: public class MainWindow extends JFrame { public void doSomething() { } public void doSomethingElse() { } private JButton button; public MainWindow() { button = new JButton(...); add(button); class ActionListener1 implements ActionListener { MainWindow parent; public ActionListener(MainWindow p) { parent = p; } public void actionPerformed(ActionEvent e) { parent.doSomething(); parent.doSomethingElse(); } } button.setActionListener(new ActionListener1(this)); } } However I hate this style ... So I tried: public abstract class ActionListenerEx<P> implements ActionListener { P parent; public ActionListenerEx(P p) { parent = p; } } public class MainWindow extends JFrame { public void doSomething() { } public void doSomethingElse() { } private JButton button; public MainWindow() { button = new JButton(...); add(button); button.setActionListener(new ActionListenerEx<MainWindow>(this) { public void actionPerformed(ActionEvent e) { parent.doSomething(); parent.doSomethingElse(); } }); } } But there's lots of Listeners beside the ActionListener ... public abstract class ActionListenerEx<LISTENER, PARENT> implements LISTENER { PARENT parent; public ActionListenerEx(PARENT p) { parent = p; } } However, it won't compile ... I am fresh at Java, and I wonder if there's already better solution.

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• JavaOne in Brazil

  - by janice.heiss(at)oracle.com

  JavaOne in Brazil, currently taking place in Sao Paolo, is one event I'd love to attend. I once heard "father of Java" James Gosling talk about Java developers throughout the world. He observed that there were good developers everywhere. It was not the case, he said, that that the really good developers are in one place and the not-so-good developers are in another. He encountered excellent developers everywhere. Then he paused and said that the craziest developers were definitely the Brazilians. As anyone who knows James would realize, this was meant as high praise. He said the Brazilians would work through the night on projects and were very enthusiastic and spontaneous - features that Brazilian culture is known for. Brazilian developers are responsible for creating one of the most impressive uses of Java ever - the applications that run the Brazilian health services. Starting from scratch they created a system that enables an expert doctor in Rio to look at an X-Ray of a patient near the Amazon and offer advice. One of the main architects of this was Java Champion Fabinane Nardon the distinguished Brazilian Java architect and open-source evangelist. As she writes in her blog:"In 2003, I was invited to assemble a team and architect a Public Healthcare Information System for the city of São Paulo, the largest in Latin America, with 14 million inhabitants. The resulting software had 2.5 million of lines of code and it was created, from specification to production, in only 10 months. At the time, the software was considered the largest J2EE application in the world and was featured in several articles, as this one. As a result, we won the Duke's Choice Award in 2005 during JavaOne, the largest development conference in the world. At the time, Sun Microsystems make a short documentary about our work." "In 2007, a lightning struck twice and I was again invited to assemble a new team and architect an even larger information system for healthcare. And thus I became CTO and one of the founders of Zilics Healthcare Information Systems. "In 2010, I started to research and work on Cloud Computing technology and became leader of the LSI-TEC Cloud Computing group. LSI-TEC is a research laboratory in the University of Sao Paulo, one of the best in Brazil. Thus, I became one of the ghost writers behind the popular Cloud Computing Twitter @the_cloud."You can see and hear Nardon in a 4 minute documentary on Java and the Brazilian health care system produced by Sun Microsystems. And you can listen to a September 2010 podcast with Nardon and her fellow Brazilian Java Champion Bruno Souza (known in Brazil as "Java Man") here at 11:10 minutes into the podcast.Next year, I'll hope to be reporting in Brazil at JavaOne!

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• Getting no class def found error. Log4J -> Java

  - by Nitesh Panchal

  Hello, I created a simple web application and added log4J's jar in my lib folder and it seems to work fine. Then i created a Ejb module and did the same thing of adding jar file in my classpath, but i am getting this error :- Caused by: javax.ejb.TransactionRolledbackLocalException: Exception thrown from bean: java.lang.NoClassDefFoundError: org/apache/log4j/Logger at com.sun.ejb.containers.BaseContainer.checkExceptionClientTx(BaseContainer.java:4929) at com.sun.ejb.containers.BaseContainer.postInvokeTx(BaseContainer.java:4761) at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:1955) ... 94 more Caused by: java.lang.NoClassDefFoundError: org/apache/log4j/Logger at common.Utils.getRssFeed(Utils.java:128) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.glassfish.ejb.security.application.EJBSecurityManager.runMethod(EJBSecurityManager.java:1052) at org.glassfish.ejb.security.application.EJBSecurityManager.invoke(EJBSecurityManager.java:1124) at com.sun.ejb.containers.BaseContainer.invokeBeanMethod(BaseContainer.java:5243) at com.sun.ejb.EjbInvocation.invokeBeanMethod(EjbInvocation.java:615) at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:797) at com.sun.ejb.EjbInvocation.proceed(EjbInvocation.java:567) at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doAround(SystemInterceptorProxy.java:157) at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.aroundInvoke(SystemInterceptorProxy.java:139) at sun.reflect.GeneratedMethodAccessor102.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at com.sun.ejb.containers.interceptors.AroundInvokeInterceptor.intercept(InterceptorManager.java:858) at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:797) at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:367) at com.sun.ejb.containers.BaseContainer.__intercept(BaseContainer.java:5215) at com.sun.ejb.containers.BaseContainer.intercept(BaseContainer.java:5203) at com.sun.ejb.containers.EJBLocalObjectInvocationHandler.invoke(EJBLocalObjectInvocationHandler.java:190) ... 92 more I don't even have any other version of log4j in classpath. Any idea why is this error coming? Actually first i created a Enterprise application and everything seemed to work fine. But then, i copied files from my enterprise application's ejb module to a separate module and since then these errors are coming. This is in my build-impl.xml :- <target depends="compile" name="library-inclusion-in-archive"> <copyfiles files="${libs.Log4J.classpath}" todir="${build.classes.dir}"/> </target> <target depends="compile" name="library-inclusion-in-manifest"> <copyfiles files="${libs.Log4J.classpath}" todir="${dist.ear.dir}/lib"/> <manifest file="${build.ear.classes.dir}/META-INF/MANIFEST.MF" mode="update"/> </target> Don't know why is this pointing to ear instead of jar. Is there any problem with the above statement? How do i resolve this? I am using Netbeans 6.8 Thanks in advance :)

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• how to configure my own formatter in java logging property file

  - by loudiyimo

  For my java project, i am using the java logging api. I want to log everything using a property file. Before using this file (log.properties), I configured my onwn fommater in the java code. (see below) Now I want to configure my own fomater in the propertie file, instead of the java code. does someone know how to do that ? Formatter formatter = new Formatter() { @Override public String format(LogRecord arg0) { StringBuilder b = new StringBuilder(); b.append(new Date()); b.append(" "); b.append(arg0.getSourceClassName()); b.append(" "); b.append(arg0.getSourceMethodName()); b.append(" "); b.append(arg0.getLevel()); b.append(" "); b.append(arg0.getMessage()); b.append(System.getProperty("line.separator")); return b.toString(); } }; fomatter in the java code ..... ..... java.util.logging.FileHandler.formatter=java.util.logging.SimpleFormatter java.util.logging.FileHandler.level=WARNING java.util.logging.??? = how can i configure my own formater in the property files with this information: data, clasename, methodename, level .etc.** formatter in de log.proprties

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• java.lang.Error: "Not enough storage is available to process this command" when generating images

  - by jhericks

  I am running a web application on BEA Weblogic 9.2. Until recently, we were using JDK 1.5.0_04, with JAI 1.1.2_01 and Image IO 1.1. In some circumstances (we never figured out exactly why), when we were processing large images (but not that large - a few MB), the JVM would crash without any error message or stack trace or anything. This didn't happen much in production, but enough to be a nuisance and eventually we were able to reproduce it. We decided to switch to JRockit90 1.5.0_04 and we were no longer able to reproduce the problem in our test environment, so we thought we had it licked. Now, however, after the application server has been up for a while, we start getting the error message, "Not enough storage is available to process this command" during image operations. For example: java.lang.Error: Error starting thread: Not enough storage is available to process this command. at java.lang.Thread.start()V(Unknown Source) at sun.awt.image.ImageFetcher$1.run(ImageFetcher.java:279) at sun.awt.image.ImageFetcher.createFetchers(ImageFetcher.java:272) at sun.awt.image.ImageFetcher.add(ImageFetcher.java:55) at sun.awt.image.InputStreamImageSource.startProduction(InputStreamImageSource.java:149) at sun.awt.image.InputStreamImageSource.addConsumer(InputStreamImageSource.java:106) at sun.awt.image.InputStreamImageSource.startProduction(InputStreamImageSource.java:144) at sun.awt.image.ImageRepresentation.startProduction(ImageRepresentation.java:647) at sun.awt.image.ImageRepresentation.prepare(ImageRepresentation.java:684) at sun.awt.SunToolkit.prepareImage(SunToolkit.java:734) at java.awt.Component.prepareImage(Component.java:3073) at java.awt.ImageMediaEntry.startLoad(MediaTracker.java:906) at java.awt.MediaEntry.getStatus(MediaTracker.java:851) at java.awt.ImageMediaEntry.getStatus(MediaTracker.java:902) at java.awt.MediaTracker.statusAll(MediaTracker.java:454) at java.awt.MediaTracker.waitForAll(MediaTracker.java:405) at java.awt.MediaTracker.waitForAll(MediaTracker.java:375) at SfxNET.System.Drawing.ImageLoader.loadImage(Ljava.awt.Image;)Ljava.awt.image.BufferedImage;(Unknown Source) at SfxNET.System.Drawing.ImageLoader.loadImage(Ljava.net.URL;)Ljava.awt.image.BufferedImage;(Unknown Source) at Resources.Tools.Commands.W$zw(Ljava.lang.ClassLoader;)V(Unknown Source) at Resources.Tools.Commands.getContents()[[Ljava.lang.Object;(Unknown Source) at SfxNET.sfxUtils.SfxResourceBundle.handleGetObject(Ljava.lang.String;)Ljava.lang.Object;(Unknown Source) at java.util.ResourceBundle.getObject(ResourceBundle.java:320) at SoftwareFX.internal.ChartFX.wxvw.yxWW(Ljava.lang.String;Z)Ljava.lang.Object;(Unknown Source) at SoftwareFX.internal.ChartFX.wxvw.vxWW(Ljava.lang.String;)Ljava.lang.Object;(Unknown Source) at SoftwareFX.internal.ChartFX.CommandBar.YWww(LSoftwareFX.internal.ChartFX.wxvw;IIII)V(Unknown Source) at SoftwareFX.internal.ChartFX.Internet.Server.xxvw.YzzW(LSoftwareFX.internal.ChartFX.Internet.Server.ChartCore;Z)LSoftwareFX.internal.ChartFX.CommandBar;(Unknown Source) at SoftwareFX.internal.ChartFX.Internet.Server.xxvw.XzzW(LSoftwareFX.internal.ChartFX.Internet.Server.ChartCore;)V(Unknown Source) at SoftwareFX.internal.ChartFX.Internet.Server.ChartCore.OnDeserialization(Ljava.lang.Object;)V(Unknown Source) at SoftwareFX.internal.ChartFX.Internet.Server.ChartCore.Zvvz(LSoftwareFX.internal.ChartFX.Base.wzzy;)V(Unknown Source) Has anyone seen something like this before? Any clue what might be happening?

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• Hidden exceptions

  - by user12617285

  Occasionally you may find yourself in a Java application environment where exceptions in your code are being caught by the application framework and either silently swallowed or converted into a generic exception. Either way, the potentially useful details of your original exception are inaccessible. Wouldn't it be nice if there was a VM option that showed the stack trace for every exception thrown, whether or not it's caught? In fact, HotSpot includes such an option: -XX:+TraceExceptions. However, this option is only available in a debug build of HotSpot (search globals.hpp for TraceExceptions). And based on a quick skim of the HotSpot source code, this option only prints the exception class and message. A more useful capability would be to have the complete stack trace printed as well as the code location catching the exception. This is what the various TraceException* options in in Maxine do (and more). That said, there is a way to achieve a limited version of the same thing with a stock standard JVM. It involves the use of the -Xbootclasspath/p non-standard option. The trick is to modify the source of java.lang.Exception by inserting the following: private static final boolean logging = System.getProperty("TraceExceptions") != null; private void log() { if (logging && sun.misc.VM.isBooted()) { printStackTrace(); } } Then every constructor simply needs to be modified to call log() just before returning: public Exception(String message) { super(message); log(); } public Exception(String message, Throwable cause) { super(message, cause); log(); } // etc... You now need to compile the modified Exception.java source and prepend the resulting class to the boot class path as well as add -DTraceExceptions to your java command line. Here's a console session showing these steps: % mkdir boot % javac -d boot Exception.java % java -DTraceExceptions -Xbootclasspath/p:boot -cp com.oracle.max.vm/bin test.output.HelloWorld java.util.zip.ZipException: error in opening zip file at java.util.zip.ZipFile.open(Native Method) at java.util.zip.ZipFile.(ZipFile.java:127) at java.util.jar.JarFile.(JarFile.java:135) at java.util.jar.JarFile.(JarFile.java:72) at sun.misc.URLClassPath$JarLoader.getJarFile(URLClassPath.java:646) at sun.misc.URLClassPath$JarLoader.access$600(URLClassPath.java:540) at sun.misc.URLClassPath$JarLoader$1.run(URLClassPath.java:607) at java.security.AccessController.doPrivileged(Native Method) at sun.misc.URLClassPath$JarLoader.ensureOpen(URLClassPath.java:599) at sun.misc.URLClassPath$JarLoader.(URLClassPath.java:583) at sun.misc.URLClassPath$3.run(URLClassPath.java:333) at java.security.AccessController.doPrivileged(Native Method) at sun.misc.URLClassPath.getLoader(URLClassPath.java:322) at sun.misc.URLClassPath.getLoader(URLClassPath.java:299) at sun.misc.URLClassPath.getResource(URLClassPath.java:168) at java.net.URLClassLoader$1.run(URLClassLoader.java:194) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at sun.misc.Launcher$ExtClassLoader.findClass(Launcher.java:229) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at java.lang.ClassLoader.loadClass(ClassLoader.java:295) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) java.security.PrivilegedActionException at java.security.AccessController.doPrivileged(Native Method) at sun.misc.URLClassPath$JarLoader.ensureOpen(URLClassPath.java:599) at sun.misc.URLClassPath$JarLoader.(URLClassPath.java:583) at sun.misc.URLClassPath$3.run(URLClassPath.java:333) at java.security.AccessController.doPrivileged(Native Method) at sun.misc.URLClassPath.getLoader(URLClassPath.java:322) ... It's worth pointing out that this is not as useful as direct VM support for tracing exceptions. It has (at least) the following limitations: The trace is shown for every exception, whether it is thrown or not. It only applies to subclasses of java.lang.Exception as there appears to be bootstrap issues when the modification is applied to Throwable.java. It does not show you where the exception was caught. It involves overriding a class in rt.jar, something should never be done in a non-development environment.

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• Remote EJB lookup issue with WebSphere 6.1

  - by marc dauncey

  I've seen this question asked before, but I've tried various solutions proposed, to no avail. Essentially, I have two EJB enterprise applications, that need to communicate with one another. The first is a web application, the second is a search server - they are located on different development servers, not in the same node, cell, or JVM, although they are on the same physical box. I'm doing the JNDI lookup via IIOP, and the URL I am using is as follows: iiop://searchserver:2819 In my hosts file, I've set searchserver to 127.0.0.1. The ports for my search server are bound to this hostname too. However, when the web app (that uses Spring btw) attempts to lookup the search EJB, it fails with the following error. This is driving me nuts, surely this kind of comms between the servers should be fairly simple to get working. I've checked the ports and they are correct. I note that the exception says the initial context is H00723Node03Cell/nodes/H00723Node03/servers/server1, name: ejb/com/hmv/dataaccess/ejb/hmvsearch/HMVSearchHome. This is the web apps server NOT the search server. Is this correct? How can I get Spring to use the right context? [08/06/10 17:14:28:655 BST] 00000028 SystemErr R org.springframework.remoting.RemoteLookupFailureException: Failed to locate remote EJB [ejb/com/hmv/dataaccess/ejb/hmvsearch/HMVSearchHome]; nested exception is javax.naming.NameNotFoundException: Context: H00723Node03Cell/nodes/H00723Node03/servers/server1, name: ejb/com/hmv/dataaccess/ejb/hmvsearch/HMVSearchHome: First component in name hmvsearch/HMVSearchHome not found. [Root exception is org.omg.CosNaming.NamingContextPackage.NotFound: IDL:omg.org/CosNaming/NamingContext/NotFound:1.0] at org.springframework.ejb.access.SimpleRemoteSlsbInvokerInterceptor.doInvoke(SimpleRemoteSlsbInvokerInterceptor.java:101) at org.springframework.ejb.access.AbstractRemoteSlsbInvokerInterceptor.invoke(AbstractRemoteSlsbInvokerInterceptor.java:140) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204) at $Proxy7.doSearchByProductKeywordsForKiosk(Unknown Source) at com.hmv.web.usecases.search.SearchUC.execute(SearchUC.java:128) at com.hmv.web.actions.search.SearchAction.executeAction(SearchAction.java:129) at com.hmv.web.actions.search.KioskSearchAction.executeAction(KioskSearchAction.java:37) at com.hmv.web.actions.HMVAbstractAction.execute(HMVAbstractAction.java:123) at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:484) at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:274) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482) at com.hmv.web.controller.HMVActionServlet.process(HMVActionServlet.java:149) at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:507) at javax.servlet.http.HttpServlet.service(HttpServlet.java:743) at javax.servlet.http.HttpServlet.service(HttpServlet.java:856) at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1282) at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1239) at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:136) at com.hmv.web.support.SessionFilter.doFilter(SessionFilter.java:137) at com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter(FilterInstanceWrapper.java:142) at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:121) at com.ibm.ws.webcontainer.filter.WebAppFilterChain._doFilter(WebAppFilterChain.java:82) at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:670) at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:2933) at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:221) at com.ibm.ws.webcontainer.VirtualHost.handleRequest(VirtualHost.java:210) at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:1912) at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:84) at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:472) at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewInformation(HttpInboundLink.java:411) at com.ibm.ws.http.channel.inbound.impl.HttpICLReadCallback.complete(HttpICLReadCallback.java:101) at com.ibm.ws.tcp.channel.impl.WorkQueueManager.requestComplete(WorkQueueManager.java:566) at com.ibm.ws.tcp.channel.impl.WorkQueueManager.attemptIO(WorkQueueManager.java:619) at com.ibm.ws.tcp.channel.impl.WorkQueueManager.workerRun(WorkQueueManager.java:952) at com.ibm.ws.tcp.channel.impl.WorkQueueManager$Worker.run(WorkQueueManager.java:1039) at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1462) Caused by: javax.naming.NameNotFoundException: Context: H00723Node03Cell/nodes/H00723Node03/servers/server1, name: ejb/com/hmv/dataaccess/ejb/hmvsearch/HMVSearchHome: First component in name hmvsearch/HMVSearchHome not found. [Root exception is org.omg.CosNaming.NamingContextPackage.NotFound: IDL:omg.org/CosNaming/NamingContext/NotFound:1.0] at com.ibm.ws.naming.jndicos.CNContextImpl.processNotFoundException(CNContextImpl.java:4392) at com.ibm.ws.naming.jndicos.CNContextImpl.doLookup(CNContextImpl.java:1752) at com.ibm.ws.naming.jndicos.CNContextImpl.doLookup(CNContextImpl.java:1707) at com.ibm.ws.naming.jndicos.CNContextImpl.lookupExt(CNContextImpl.java:1412) at com.ibm.ws.naming.jndicos.CNContextImpl.lookup(CNContextImpl.java:1290) at com.ibm.ws.naming.util.WsnInitCtx.lookup(WsnInitCtx.java:145) at javax.naming.InitialContext.lookup(InitialContext.java:361) at org.springframework.jndi.JndiTemplate$1.doInContext(JndiTemplate.java:132) at org.springframework.jndi.JndiTemplate.execute(JndiTemplate.java:88) at org.springframework.jndi.JndiTemplate.lookup(JndiTemplate.java:130) at org.springframework.jndi.JndiTemplate.lookup(JndiTemplate.java:155) at org.springframework.jndi.JndiLocatorSupport.lookup(JndiLocatorSupport.java:95) at org.springframework.jndi.JndiObjectLocator.lookup(JndiObjectLocator.java:105) at org.springframework.ejb.access.AbstractRemoteSlsbInvokerInterceptor.lookup(AbstractRemoteSlsbInvokerInterceptor.java:98) at org.springframework.ejb.access.AbstractSlsbInvokerInterceptor.getHome(AbstractSlsbInvokerInterceptor.java:143) at org.springframework.ejb.access.AbstractSlsbInvokerInterceptor.create(AbstractSlsbInvokerInterceptor.java:172) at org.springframework.ejb.access.AbstractRemoteSlsbInvokerInterceptor.newSessionBeanInstance(AbstractRemoteSlsbInvokerInterceptor.java:226) at org.springframework.ejb.access.SimpleRemoteSlsbInvokerInterceptor.getSessionBeanInstance(SimpleRemoteSlsbInvokerInterceptor.java:141) at org.springframework.ejb.access.SimpleRemoteSlsbInvokerInterceptor.doInvoke(SimpleRemoteSlsbInvokerInterceptor.java:97) ... 36 more Many thanks for any assistance! Marc

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• Python productivity VS Java Productivity

  - by toc777

  Over on SO I came across a question regarding which platform, Java or Python is best for developing on Google AppEngine. Many people were boasting of the increased productivity gained from using Python over Java. One thing I would say about the Python vs Java productivity argument, is Java has excellent IDE's to speed up development where as Python is really lacking in this area because of its dynamic nature. So even though I prefer to use Python as a language, I don't believe it gives quite the productivity boost compared to Java especially when using a new framework. Obviously if it were Java vs Python and the only editor you could use was VIM then Python would give you a huge productivity boost but when IDE's are brought into the equation its not as clear cut. I think Java's merits are often solely evaluated on a language level and often on out dated assumptions but Java has many benefits external to the language itself, e.g the JVM (often criticized but offers huge potential), excellent IDE's and tools, huge numbers of third party libraries, platforms etc.. Question, Does Python/related dynamic languages really give the huge productivity boosts often talked about? (with consideration given to using new frameworks and working with medium to large applications).

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• Python productivity VS Java Productivity

  - by toc777

  Over on SO I came across a question regarding which platform, Java or Python is best for developing on Google AppEngine. Many people were boasting of the increased productivity gained from using Python over Java. One thing I would say about the Python vs Java productivity argument, is Java has excellent IDE's to speed up development where as Python is really lacking in this area because of its dynamic nature. So even though I prefer to use Python as a language, I don't believe it gives quite the productivity boost compared to Java especially when using a new framework. Obviously if it were Java vs Python and the only editor you could use was VIM then Python would give you a huge productivity boost but when IDE's are brought into the equation its not as clear cut. I think Java's merits are often solely evaluated on a language level and often on out dated assumptions but Java has many benefits external to the language itself, e.g the JVM (often criticized but offers huge potential), excellent IDE's and tools, huge numbers of third party libraries, platforms etc.. Question, Does Python/related dynamic languages really give the huge productivity boosts often talked about? (with consideration given to using new frameworks and working with medium to large applications).

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• how to double buffer in multiple classes with java

  - by kdavis8

  I am creating a Java 2D video game. I can load graphics just fine, but when it gets into double buffering I have issues. My source code package myPackage; import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Image; import java.awt.Toolkit; import java.awt.image.BufferStrategy; import java.awt.image.BufferedImage; import javax.swing.JFrame; public class GameView extends JFrame { private BufferedImage backbuffer; private Graphics2D g2d; public GameView() { setBounds(0, 0, 500, 500); setVisible(true); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); backbuffer = new BufferedImage(getHeight(), getWidth(), BufferedImage.TYPE_INT_BGR); g2d = backbuffer.createGraphics(); Toolkit tk = Toolkit.getDefaultToolkit(); Image img = tk.getImage(this.getClass().getResource("cage.png")); g2d.setColor(Color.red); //g2d.drawString("Hello",100,100); g2d.drawImage(img, 100, 100, this); repaint(); } public static void main(String args[]) { new GameView(); } public void paint(Graphics g) { g2d = (Graphics2D)g; g2d.drawImage(backbuffer, 0, 0, this); } }

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• Why doesn't Java allow for the creaton of generic arrays?

  - by byte

  There are plenty of questions on stackoverflow from people who have attempted to create an array of generics like so: ArrayList<Foo>[] poo = new ArrayList<Foo>[5]; And the answer of course is that the Java specification doesn't allow you to declare an array of generics. My question however is why ? What is the technical reason underlying this restriction in the java language or java vm? It's a technical curiosity I've always wondered about.

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• Why does NUnit ignore datapoints when using generics in a theory

  - by The Chairman

  I'm trying to make use of the TheoryAttribute, introduced in NUnit 2.5. Everything works fine as long as the arguments are of a defined type: [Datapoint] public double[,] Array2X2 = new double[,] { { 1, 0 }, { 0, 1 } }; [Theory] public void TestForArbitraryArray(double[,] array) { // ... } It does not work, when I use generics: [Datapoint] public double[,] Array2X2 = new double[,] { { 1, 0 }, { 0, 1 } }; [Theory] public void TestForArbitraryArray<T>(T[,] array) { // ... } NUnit gives a warning saying No arguments were provided. Why is that?

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• JMS ConnectionFactory creation error WSVR0073W

  - by scottyab

  I must confess I’m not a JMS aficionado, one of our guys has written a Java webservice client [postcode lookup web service] and from a Remote Java client are calling a Message Driven Bean running in Websphere 6.1, using JMS. Getting the following error when attempted to create the Connection Factory. To which configured within Websphere jms/WSProxyQueueConnectionFactory. WARNING: WSVR0073W. Googling WSVR0073W yields little, the error code is an unknown error. Can anyone shed any light on potential issues creating the connection factory. Code Hashtable env = new Hashtable(); env.put(Context.INITIAL_CONTEXT_FACTORY, contextFactoryName); env.put(Context.PROVIDER_URL, providerURL); env.put("com.ibm.CORBA.ORBInit","com.ibm.ws.sib.client.ORB"); namingContext = new InitialContext(env); System.out.println("callRemoteService: get connectionFactoriy, request/response queues, session. Naming contex env =" + env); // Find everything we need to communicate... connectionFactory = (QueueConnectionFactory) namingContext.lookup(getQueueConnectionFactoryName()); requestQueue = (Queue) namingContext.lookup(getRequestQueueName()); Console output: calling RemoteService with hostname[MyServer:2813] and postcode[M4E 3W1]callRemoteService hostname[MyServer:2813] messess text[M4E 3W1] callRemoteService: get connectionFactoriy, request/response queues, session. Naming contex env ={com.ibm.CORBA.ORBInit=com.ibm.ws.sib.client.ORB, java.naming.provider.url=iiop:// MyServer:2813/, java.naming.factory.initial=com.ibm.websphere.naming.WsnInitialContextFactory} 05-Jan-2011 13:51:04 null null WARNING: WSVR0073W 05-Jan-2011 13:51:05 null null WARNING: jndiGetObjInstErr 05-Jan-2011 13:51:05 null null WARNING: jndiNamingException callRemoteService: closing connections and resources com.ibm.websphere.naming.CannotInstantiateObjectException: Exception occurred while the JNDI NamingManager was processing a javax.naming.Reference object. [Root exception is java.lang.NoClassDefFoundError: Invalid Implementation Key, com.ibm.ws.transaction.NonRecovWSTxManager] at com.ibm.ws.naming.util.Helpers.processSerializedObjectForLookupExt(Helpers.java:1000) at com.ibm.ws.naming.util.Helpers.processSerializedObjectForLookup(Helpers.java:705) at com.ibm.ws.naming.jndicos.CNContextImpl.processResolveResults(CNContextImpl.java:2097) at com.ibm.ws.naming.jndicos.CNContextImpl.doLookup(CNContextImpl.java:1951) at com.ibm.ws.naming.jndicos.CNContextImpl.doLookup(CNContextImpl.java:1866) at com.ibm.ws.naming.jndicos.CNContextImpl.lookupExt(CNContextImpl.java:1556) at com.ibm.ws.naming.jndicos.CNContextImpl.lookup(CNContextImpl.java:1358) at com.ibm.ws.naming.util.WsnInitCtx.lookup(WsnInitCtx.java:172) at javax.naming.InitialContext.lookup(InitialContext.java:450) at com.das.jms.clients.BaseWSProxyClient.callRemoteService(BaseWSProxyClient.java:180) at com.das.jms.clients.RemotePostCodeLookup.findAddress(RemotePostCodeLookup.java:38) at com.das.jms.RemoteServiceAccess.findAddress(RemoteServiceAccess.java:80) at com.das.jms.TestRemoteAccess.testSuccessLookup(TestRemoteAccess.java:20) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37) at java.lang.reflect.Method.invoke(Method.java:599) at junit.framework.TestCase.runTest(TestCase.java:168) at junit.framework.TestCase.runBare(TestCase.java:134) at junit.framework.TestResult$1.protect(TestResult.java:110) at junit.framework.TestResult.runProtected(TestResult.java:128) at junit.framework.TestResult.run(TestResult.java:113) at junit.framework.TestCase.run(TestCase.java:124) at junit.framework.TestSuite.runTest(TestSuite.java:232) at junit.framework.TestSuite.run(TestSuite.java:227) at org.junit.internal.runners.OldTestClassRunner.run(OldTestClassRunner.java:76) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:45) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)com.ibm.websphere.naming.CannotInstantiateObjectException: Exception occurred while the JNDI NamingManager was processing a javax.naming.Reference object. [Root exception is java.lang.NoClassDefFoundError: Invalid Implementation Key, com.ibm.ws.transaction.NonRecovWSTxManager] [[B@4d794d79 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196) Caused by: java.lang.NoClassDefFoundError: Invalid Implementation Key, com.ibm.ws.transaction.NonRecovWSTxManager at com.ibm.ws.Transaction.TransactionManagerFactory.getUOWCurrent(TransactionManagerFactory.java:125) at com.ibm.ws.rsadapter.AdapterUtil.<clinit>(AdapterUtil.java:271) at java.lang.J9VMInternals.initializeImpl(Native Method) at java.lang.J9VMInternals.initialize(J9VMInternals.java:200) at com.ibm.ejs.j2c.ConnectionFactoryBuilderImpl.getObjectInstance(ConnectionFactoryBuilderImpl.java:281) at javax.naming.spi.NamingManager.getObjectInstanceByFactoryInReference(NamingManager.java:480) at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:345) at com.ibm.ws.naming.util.Helpers.processSerializedObjectForLookupExt(Helpers.java:896) ... 31 more

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• Using Generics to typecast object type to generic type

  - by Shantanu Gupta

  I am very new to generics and trying to implement it. How can i use it here. private T returnValueFromGrid(int RowNo, int ColNo) { return Converter<dgvCurrencyMaster.Rows[RowNo].Cells[ColNo].Value,T>; } I am trying to convert below value to generic type and then return it. dgvCurrencyMaster.Rows[RowNo].Cells[ColNo].Value Here i need to know two things. How to do the above problem and how to use this in my code. Please provide some eg.

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• Java generics: What is the compiler's issue here? ("no unique maximal instance")

  - by Epaga

  I have the following methods: public <T> T fromJson( Reader jsonData, Class<T> clazz ) { return fromJson( jsonData, (Type)clazz ); } public <T> T fromJson( Reader jsonData, Type clazz ) { ... } The compiler is saying about the first method: type parameters of <T>T cannot be determined; no unique maximal instance exists for type variable T with upper bounds T,java.lang.Object return fromJson( jsonData, (Type)clazz ); ^ What is the problem?

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• Can't seem to redirect from a ViewScoped constructor.

  - by Andrew

  I'm having trouble redirecting from a view scoped bean in the case that we don't have the required info for the page in question. The log entry in the @PostContruct is visible in the log right before a NPE relating to the view trying to render itself instead of following my redirect. Why is it ignoring the redirect? Here's my code: @ManagedBean public class WelcomeView { private String sParam; private String aParam; public WelcomeView() { super(); sParam = getURL_Param("surveyName"); aParam = getURL_Param("accountName"); project = fetchProject(sParam, aParam); } @PostConstruct public void redirectWithoutProject() { if (null == project) { try { logger.warn("NO project [" + sParam + "] for account [" + aParam + "]"); FacesContext fc = FacesContext.getCurrentInstance(); fc.getExternalContext().redirect("/errors/noSurvey.jsf"); return; } catch (Exception e) { e.printStackTrace(); } } } .... public boolean getAuthenticated() { if (project.getPasswordProtected()) { return enteredPassword.equals(project.getLoginPassword()); } else return true; } } Here's the stack trace: SEVERE: Error Rendering View[/participant/welcome.xhtml] javax.el.ELException: /templates/participant/welcome.xhtml @80,70 rendered="#{welcomeView.authenticated}": Error reading 'authenticated' on type com.MYCODE.general.controllers.participant.WelcomeView at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:107) at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:190) at javax.faces.component.UIComponentBase.isRendered(UIComponentBase.java:416) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1607) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616) at javax.faces.render.Renderer.encodeChildren(Renderer.java:168) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:848) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1613) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616) at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:380) at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:126) at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:127) at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139) at javax.faces.webapp.FacesServlet.service(FacesServlet.java:313) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at com.MYCODE.general.filters.StatsFilter.doFilter(StatsFilter.java:28) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:568) at org.apache.catalina.authenticator.SingleSignOn.invoke(SingleSignOn.java:421) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) at java.lang.Thread.run(Thread.java:637) Caused by: java.lang.NullPointerException at com.MYCODE.general.controllers.participant.WelcomeView$$M$863c205f.getAuthenticated(WelcomeView.java:127) at com.MYCODE.general.controllers.participant.WelcomeView$$A$863c205f.getAuthenticated(<generated>) at com.MYCODE.general.controllers.participant.WelcomeView.getAuthenticated(WelcomeView.java:125) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at javax.el.BeanELResolver.getValue(BeanELResolver.java:62) at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:53) at com.sun.faces.el.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:72) at org.apache.el.parser.AstValue.getValue(AstValue.java:118) at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:186) at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:102) ... 33 more

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• How To Get Type Info Without Using Generics?

  - by DaveDev

  Hi Guys I have an object obj that is passed into a helper method. public static MyTagGenerateTag<T>(this HtmlHelper htmlHelper, T obj /*, ... */) { Type t = typeof(T); foreach (PropertyInfo prop in t.GetProperties()) { object propValue = prop.GetValue(obj, null); string stringValue = propValue.ToString(); dictionary.Add(prop.Name, stringValue); } // implement GenerateTag } I've been told this is not a correct use of generics. Can somebody tell me if I can achieve the same result without specifying a generic type? If so, how? I would probably change the signature so it'd be like: public static MyTag GenerateTag(this HtmlHelper htmlHelper, object obj /*, ... */) { Type t = typeof(obj); // implement GenerateTag } but Type t = typeof(obj); is impossible. Any suggestions? Thanks Dave

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• What is the problem with this Java code dealing with Generics?

  - by devoured elysium

  interface Addable<E> { public E add(E x); public E sub(E y); public E zero(); } class SumSet<E extends Addable> implements Set<E> { private E element; public SumSet(E element) { this.element = element; } public E getSum() { return element.add(element.zero()); } } It seems that element.add() doesn't return an E extends Addable but rather an Object. Why is that? Has it anything to do with Java not knowing at run-time what the object types really are, so it just assumes them to be Objects(thus requiring a cast)? Thanks

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• C5 Generics Collection IntervalHeap<T> -- getting an IPriorityQueueHandle from a T for Replace or De

  - by Jared Updike

  I'm using the Generics Collection library C5 (server down :-( ) and I have an IntervalHeap(T) and I need to Delete or Replace a T that is not the Max or Min. How do I get an IPriorityQueueHandle from my T? The C5 library source code shows that IPriorityQueueHandle(T) has no methods or properties to implement and the compiler thinks my implementation of IPriorityQueueHandle(T) for my T is acceptable. I try to use a T like this: q.Replace(t, t); and the C5 library throws an InvalidCastException because it cannot convert my T to a (Handle).

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• .NET 2.0: Invoking Methods Using Reflection And Generics Causes Exception

  - by David Derringer

  Hi all, I'm new to Stack Overflow, so forgive me. I've just started transititoning over to C# and I am stuck on a problem. I am wanting to pass a generic class in and call a method from that class. So, my code looks as such: public void UpdateRecords<T>(T sender) where T : new() //where T: new() came from Resharper { Type foo = Type.GetType(sender.GetType().ToString()); object[] userParameters = new object[2]; userParameters[0] = x; userParameters[1] = y; sender = new T(); //This was to see if I could solve my exception problem MethodInfo populateRecord = foo.GetMethod("MethodInOtherClass"); populateMethod.Invoke(sender, userParameters); } Exception thrown: "Object reference not set to an instance of an object." Again, I really apologize, as I am nearly brand new to C# and this is the first time I've ever handled reflection and generics. Thank you!

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• How to avoid Eclipse warnings when using legacy code without generics?

  - by Paul Crowley

  I'm using JSON.simple to generate JSON output from Java. But every time I call jsonobj.put("this", "that"), I see a warning in Eclipse: Type safety: The method put(Object, Object) belongs to the raw type HashMap. References to generic type HashMap should be parameterized The clean fix would be if JSONObject were genericized, but since it isn't, I can't add any generic type parameters to fix this. I'd like to switch off as few warnings as possible, so adding "@SuppressWarnings("unchecked")" to lots of methods is unappealing, but do I have any other option besides putting up with the warnings?

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• Create instance of generic type in Java?

  - by David Citron

  Is it possible to create an instance of a generic type in Java? I'm thinking based on what I've seen that the answer is "no" (due to type erasure), but I'd be interested if anyone can see something I'm missing: class SomeContainer<E> { E createContents() { return what??? } } EDIT: It turns out that Super Type Tokens could be used to resolve my issue, but it requires a lot of reflection-based code, as some of the answers below have indicated. I'll leave this open for a little while to see if anyone comes up with anything dramatically different than Ian Robertson's Artima Article.

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• How do I map nested generics in NHibernate

  - by Gluip

  In NHibernate you can map generics like this <class name="Units.Parameter`1[System.Int32], Units" table="parameter_int" > </class> But how can I map a class like this? Set<T> where T is a Parameter<int> like this Set<Parameter<int>> My mapping hbm.xml looking like this fails <class name="Set`1[[Units.Parameter`1[System.Int32], Units]],Units" table="settable"/> I simplified my mappings a little to get my point accross very clearly. Basically I want NHibernate to map generic class which has has generic type parameter. Want I understand from googling around is that NHibernate is not able to parse the name to the correct type in TypeNameParser.Parse() which result in the following error when adding the mapping to the configuration System.ArgumentException: Exception of type 'System.ArgumentException' was thrown. Parameter name: typeName@31 Anybody found a way around this limitation?

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