Roland Käser [http://community.jboss.org/people/roli82001] created the discussion
"Problems with the tomcat classloader" To view the discussion, visit: http://community.jboss.org/message/639418#639418 -------------------------------------------------------------- Hello While developing a very small and lightweight j2ee linke server, I try to extend a abstract class at runtime using: ClassPool pool = ClassPool.getDefault(); pool.insertClassPath(new ClassClassPath(this.getClass())); CtClass cc = pool.makeClass("HelloWorldClientBean"); cc.setSuperclass(pool.get("ch.isn.dante.comserver.test.HelloWorldSessionBean")); Class beanClass = cc.toClass(); cc.defrost(); Constructor constructor = beanClass.getConstructor(argsClass); Object[] params = new Object[]{new ComServerSession(),null}; HelloWorldSessionBean sessionBean = (HelloWorldSessionBean)constructor.newInstance(params); System.out.println("Hello World Output: " + sessionBean.getHelloWorld()); This works fine on the client side (regular java vm). On the server side I get first a very strange exception which was stangely related to the tomcats classloader. javassist.CannotCompileException: by java.lang.LinkageError: loader (instance of org/apache/catalina/loader/WebappClassLoader): attempted duplicate class definition for name: "ch/isn/dante/comserver/test/HelloWorldSessionBeanExecutable" javassist.CannotCompileException: by java.lang.LinkageError: loader (instance of org/apache/catalina/loader/WebappClassLoader): attempted duplicate class definition for name: "ch/isn/dante/comserver/test/HelloWorldSessionBeanExecutable" at javassist.ClassPool.toClass(ClassPool.java:1089) at javassist.ClassPool.toClass(ClassPool.java:1032) at javassist.ClassPool.toClass(ClassPool.java:990) at javassist.CtClass.toClass(CtClass.java:1125) ... Caused by: java.lang.LinkageError: loader (instance of org/apache/catalina/loader/WebappClassLoader): attempted duplicate class definition for name: "ch/isn/dante/comserver/test/HelloWorldSessionBeanExecutable" at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631) at java.lang.ClassLoader.defineClass(ClassLoader.java:615) at java.lang.ClassLoader.defineClass(ClassLoader.java:465) 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 javassist.ClassPool.toClass2(ClassPool.java:1102) at javassist.ClassPool.toClass(ClassPool.java:1083) To prevent this I wrote a very ugly hack to use the system class loader and add the classpath in which this superclass: | | | | URL url = new File(serverServlet.getInstallDir() + "WEB-INF/classes/").toURL(); | | | | | URLClassLoader sysloader = (URLClassLoader) ClassLoader.getSystemClassLoader(); | | | | | Class sysclass = URLClassLoader.class; | | | | | | | | | | Method method = sysclass.getDeclaredMethod("addURL", parameters); | | | | | method.setAccessible(true); | | | | | method.invoke(sysloader, new Object[]{url}); | and created the class using this modified classloader: | | | Class beanClass = cc.toClass(sysloader); | | | | | | | cc.defrost(); | Now I get a NoSuchMethodException: java.lang.NoSuchMethodException: HelloWorldServerBean.<init>(ch.isn.dante.comserver.server.ComServerSession, ch.isn.dante.comserver.server.ServerApplication) at java.lang.Class.getConstructor0(Class.java:2706) at java.lang.Class.getConstructor(Class.java:1657) at ch.isn.dante.comserver.server.ComServerSession.loadClass(ComServerSession.java:239) at ch.isn.dante.comserver.server.ComServer.doGet(ComServer.java:286) at ch.isn.dante.comserver.server.ComServer.doPost(ComServer.java:417) at javax.servlet.http.HttpServlet.service(HttpServlet.java:647) at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) I can't see from which this error comes. When I inspect the newly created class I get one constructor: public HelloWorldClientBean(ch.isn.dante.comserver.server.ComServerSession,ch.isn.dante.comserver.server.ServerApplication) -------------------------------------------------------------- Reply to this message by going to Community [http://community.jboss.org/message/639418#639418] Start a new discussion in Javassist at Community [http://community.jboss.org/choose-container!input.jspa?contentType=1&containerType=14&container=2062]
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