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POLoading classes using Spring inside an eclipse OSGi container does not seem to work. Fix?
 

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  1. POLoading classes using Spring inside an eclipse OSGi container does not seem to work. Fix?
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    <p>I am somewhat puzzled about Spring's classloading behavior inside an eclipse OSGi container (which is the basis for the TIBCO ActiveMatrix runtime I am trying to get this running on) and boiled this down to the below simple example.</p> <p>In it (the TestComponent object is created and called inside an OSGi bundle's Activator class, but I don't think that this is important here) I first create an object direcly, just to double-check, that its class exists and can be instantiated. This of course works as one would expect... Second, I want to create a second object of that very same class using Spring (as I originally intended), but this fails with a ClassNotFoundException. </p> <p>Spring claims, it can't find that class (even though the package and class name definitely match), so I even added a .setClassLoader(...) call to pass it the very same classloader that just successfully loaded that very same class, but Spring still fails to locate that class. Any clue of why that is so? I have ran out of ideas. What am I missing?</p> <p>Later edit: I just had to realize, that it is NOT the ...getBean(...)-method call that crashes, but rather already the ClassPathXmlApplicationContext()-constructor. I.e. the object is already created in that constructor and not only later in the subsequent getBean(...)-method call. Thus my attempt to pass-in the classloader is futile as it already comes to late. So the question thus rather is: how can I pass-in the context's class loader to that constructor (or to the factory or whatever Spring uses internally to create the ClassPathXmlApplicationContext object)?</p> <p>My example:</p> <p>I first defined an interface for the class to be created via Spring:</p> <pre><code>package com.example.some_package_0; public interface SomeInterface { public String getSomeString(); } </code></pre> <p>... and a class, implementing this interface:</p> <pre><code>package com.example.some_package_1; import com.example.some_package_0.SomeInterface; public class SomeClassA implements SomeInterface { private String someProperty; public void setSomeProperty(String someProperty) { this.someProperty = someProperty; } public String getSomeString() { return this.someProperty; } } </code></pre> <p>My Test-program reads</p> <pre><code>public class TestComponent { import com.example.some_package_0.SomeInterface; import com.example.some_package_1.SomeClassA; public void test() { SomeClassA obj1 = new SomeClassA(); obj1.setSomeProperty("SomeClassA-object (directly created)"); System.out.println("@@ message=\"" + obj1.getSomeString() + "\""); ClassPathXmlApplicationContext applicationContext; applicationContext = new ClassPathXmlApplicationContext("/META-INF/package1_beans.xml"); applicationContext.setClassLoader(Thread.currentThread().getContextClassLoader()); SomeInterface obj2 = (SomeInterface) applicationContext.getBean("bean1"); System.out.println("@@ message=\"" + obj2.getSomeString() + "\""); } } </code></pre> <p>The /META-INF/package1_beans.xml being used reads:</p> <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans classpath:/org/springframework/beans/factory/xml/spring-beans-2.5.xsd"&gt; &lt;bean id="bean1" class="com.example.some_package_1.SomeClassA"&gt; &lt;property name="someProperty"&gt;&lt;value&gt;SomeClassA-object (created via Spring)&lt;/value&gt;&lt;/property&gt; &lt;/bean&gt; &lt;/beans&gt; </code></pre> <p>The exception reads:</p> <pre><code>org.springframework.beans.factory.CannotLoadBeanClassException: Cannot find class [com.example.some_package_1.SomeClassA] for bean with name 'bean1' defined in class path resource [META-INF/package1_beans.xml]; nested exception is java.lang.ClassNotFoundException: com.example.some_package_1.SomeClassA at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1141) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:524) at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1177) at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:758) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:422) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:728) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:380) at org.springframework.context.support.ClassPathXmlApplicationContext.&lt;init&gt;(ClassPathXmlApplicationContext.java:139) at org.springframework.context.support.ClassPathXmlApplicationContext.&lt;init&gt;(ClassPathXmlApplicationContext.java:83) at com.example.test_spring_example.TestComponent.testOperation(TestComponent.java:71) 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 com.tibco.amf.platform.runtime.componentframework.internal.proxies.operation.OperationHandler.invokeMethodWithThreadContext(OperationHandler.java:667) at com.tibco.amf.platform.runtime.componentframework.internal.proxies.operation.AsyncToSyncOperationHandler.invoke(AsyncToSyncOperationHandler.java:98) at com.tibco.amf.platform.runtime.componentframework.internal.proxies.ProxyInvocationHandlerRegistry$ProxyInvocationContext.invoke(ProxyInvocationHandlerRegistry.java:411) at $Proxy67.invoke(Unknown Source) at com.tibco.amf.binding.soap.runtime.transport.http.SoapHttpInboundEndpoint.processHttpPost(SoapHttpInboundEndpoint.java:565) at com.tibco.amf.binding.soap.runtime.transport.http.SoapHttpServer.doPost(SoapHttpServer.java:195) at javax.servlet.http.HttpServlet.service(HttpServlet.java:710) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:502) at org.mortbay.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1213) at com.tibco.governance.pa.amxcomponent.pep.http.HttpPepFilter.doFilter(HttpPepFilter.java:126) at org.mortbay.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1205) at com.tibco.amf.implementation.common.httpfilter.GenericComponentFilter.doFilter(GenericComponentFilter.java:65) at org.mortbay.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1205) at com.tibco.amf.hpa.tibcohost.jetty.internal.ConnectorFilter.doFilter(ConnectorFilter.java:49) at org.mortbay.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1205) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765) at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230) at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:326) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:536) at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:928) at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:747) at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:405) at org.mortbay.jetty.bio.SocketConnector$Connection.run(SocketConnector.java:228) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:662) Caused by: java.lang.ClassNotFoundException: com.example.some_package_1.SomeClassA at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:513) at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:429) at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:417) at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:107) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) at org.springframework.util.ClassUtils.forName(ClassUtils.java:211) at org.springframework.beans.factory.support.AbstractBeanDefinition.resolveBeanClass(AbstractBeanDefinition.java:385) at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1138) ... 46 more </code></pre>
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    1. CO`ClassNotFOundException` is a common theme with OSGi! Try exporting this package from your MANIFEST: com.example.some_package_1 Failing that may be useful to see the MANIFEST
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    2. CODuplicate of http://stackoverflow.com/questions/8039931/how-to-use-a-spring-bean-inside-a-osgi-bundle/8067534#8067534
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      1. POLoading classes using Spring inside an eclipse OSGi container does not seem to work. Fix?
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    3. CO@Robin: while I don't agree that this is a duplicate of the referenced question, the discussion there made me at least aware, that in OSGi the current's thread classloader and the bundle's classloader are not necessarily the same. That allowed me to search on and I found this thread: http://tomsondev.bestsolution.at/2011/10/15/find-classloader-for-a-given-osgi-bundle/. The "trick" shown there IMHO is not exactly nice, "clean" or future-proof (since it requires quite some inside knowledge of OSGi and references an OSGi internal class) it actually DOES work. So, thanks for the pointer!
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