package org.jboss.book.jmx.ex0;import java.io.File;import java.net.URL;import org.apache.log4j.Logger;import org.jboss.util.ChapterExRepository;import org.jboss.util.Debug;/** An example of a LinkageError due to classes being defined by more than * one class loader in a non-standard class loading environment. * @author Scott.Stark@jboss.org * @version $Revision: 1.1 $ */public class ExLE{   public static void main(String[] args) throws Exception   {      ChapterExRepository.init(ExLE.class);      String chapDir = System.getProperty("chapter.dir");      Logger ucl0Log = Logger.getLogger("UCL0");      File jar0 = new File(chapDir+"/j0.jar");      ucl0Log.info("jar0 path: "+jar0.toString());      URL[] cp0 = {jar0.toURL()};      Ex0URLClassLoader ucl0 = new Ex0URLClassLoader(cp0);      Thread.currentThread().setContextClassLoader(ucl0);      Class ctxClass1 = ucl0.loadClass("org.jboss.book.jmx.ex0.ExCtx");      Class obj2Class1 = ucl0.loadClass("org.jboss.book.jmx.ex0.ExObj2");      StringBuffer buffer = new StringBuffer("ExCtx Info");      Debug.displayClassInfo(ctxClass1, buffer, false);      ucl0Log.info(buffer.toString());      buffer.setLength(0);      buffer.append("ExObj2 Info, UCL0");      Debug.displayClassInfo(obj2Class1, buffer, false);      ucl0Log.info(buffer.toString());      File jar1 = new File(chapDir+"/j1.jar");      Logger ucl1Log = Logger.getLogger("UCL1");      ucl1Log.info("jar1 path: "+jar1.toString());      URL[] cp1 = {jar1.toURL()};      Ex0URLClassLoader ucl1 = new Ex0URLClassLoader(cp1);      Class obj2Class2 = ucl1.loadClass("org.jboss.book.jmx.ex0.ExObj2");      buffer.setLength(0);      buffer.append("ExObj2 Info, UCL1");      Debug.displayClassInfo(obj2Class2, buffer, false);      ucl1Log.info(buffer.toString());      ucl0.setDelegate(ucl1);      try      {         ucl0Log.info("Try ExCtx.newInstance()");         Object ctx0 = ctxClass1.newInstance();         ucl0Log.info("ExCtx.ctor succeeded, ctx0: "+ctx0);      }      catch(Throwable e)      {         ucl0Log.error("ExCtx.ctor failed", e);      }   }}