package org.jboss.book.jmx.ex0;import java.io.File;import java.net.URL;import java.net.URLClassLoader;import java.lang.reflect.Method;import org.apache.log4j.Logger;import org.jboss.util.ChapterExRepository;import org.jboss.util.Debug;/** An example of a ClassCastException that results from classes loaded through * different class loaders. * @author Scott.Stark@jboss.org * @version $Revision: 1.1 $ */public class ExCCEc{   public static void main(String[] args) throws Exception   {      ChapterExRepository.init(ExCCEc.class);      String chapDir = System.getProperty("chapter.dir");      Logger ucl0Log = Logger.getLogger("UCL0");      // Load ExObj from j0.jar using URLClassLoader instance 0      File jar0 = new File(chapDir+"/j0.jar");      ucl0Log.info("jar0 path: "+jar0.toString());      URL[] cp0 = {jar0.toURL()};      URLClassLoader ucl0 = new URLClassLoader(cp0);      Thread.currentThread().setContextClassLoader(ucl0);      Class objClass = ucl0.loadClass("org.jboss.book.jmx.ex0.ExObj");      StringBuffer buffer = new StringBuffer("ExObj Info");      Debug.displayClassInfo(objClass, buffer, false);      ucl0Log.info(buffer.toString());      Object value = objClass.newInstance();      // Load ExCtx from j0.jar using URLClassLoader instance 1      File jar1 = new File(chapDir+"/j0.jar");      Logger ucl1Log = Logger.getLogger("UCL1");      ucl1Log.info("jar1 path: "+jar1.toString());      URL[] cp1 = {jar1.toURL()};      URLClassLoader ucl1 = new URLClassLoader(cp1);      Thread.currentThread().setContextClassLoader(ucl1);      Class ctxClass2 = ucl1.loadClass("org.jboss.book.jmx.ex0.ExCtx");      buffer.setLength(0);      buffer.append("ExCtx Info");      Debug.displayClassInfo(ctxClass2, buffer, false);      ucl1Log.info(buffer.toString());      Object ctx2 = ctxClass2.newInstance();      try      {         // Invoke ExCtx[UCL1].useValue(value=ExObj[UCL0]) via reflection         Class[] types = {Object.class};         Method useValue = ctxClass2.getMethod("useValue", types);         Object[] margs = {value};         useValue.invoke(ctx2, margs);      }      catch(Exception e)      {         ucl1Log.error("Failed to invoke ExCtx.useValue", e);         throw e;      }   }}