1.错误：
 !ENTRY org.eclipse.osgi 4 0 2012-02-01 06:52:52.473
!MESSAGE
!STACK 0
org.osgi.framework.BundleException: Exception in org.eclipse.osgi.framework.internal.core.SystemBundleActivator.start() of bundle org.eclipse.osgi.
    at org.eclipse.osgi.framework.internal.core.BundleContextImpl.startActivator(BundleContextImpl.java:1018)
    at org.eclipse.osgi.framework.internal.core.BundleContextImpl.start(BundleContextImpl.java:974)
    at org.eclipse.osgi.framework.internal.core.StartLevelManager.resumeBundles(StartLevelManager.java:611)
    at org.eclipse.osgi.framework.internal.core.StartLevelManager.incFWSL(StartLevelManager.java:497)
    at org.eclipse.osgi.framework.internal.core.StartLevelManager.doSetStartLevel(StartLevelManager.java:282)
    at org.eclipse.osgi.framework.internal.core.StartLevelManager.launch(StartLevelManager.java:250)
    at org.eclipse.osgi.framework.internal.core.SystemBundle.resume(SystemBundle.java:153)
    at org.eclipse.osgi.framework.internal.core.Framework.launch(Framework.java:588)
    at org.eclipse.osgi.framework.internal.core.OSGi.launch(OSGi.java:51)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.startup(EclipseStarter.java:289)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:172)
    at java.lang.reflect.Method.invoke(Native Method)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:508)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:447)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1173)
    at org.eclipse.equinox.launcher.Main.main(Main.java:1148)
Root exception:
java.lang.NoClassDefFoundError: org/xml/sax/helpers/DefaultHandler
    at java.lang.ClassLoader.defineClass0(Native Method)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$100(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClassInternal(Unknown Source)
    at org.eclipse.core.runtime.internal.adaptor.PluginConverterImpl.parsePluginInfo(PluginConverterImpl.java:589)
    at org.eclipse.core.runtime.internal.adaptor.PluginConverterImpl.fillPluginInfo(PluginConverterImpl.java:108)
    at org.eclipse.core.runtime.internal.adaptor.PluginConverterImpl.convertManifest(PluginConverterImpl.java:707)
    at org.eclipse.core.runtime.internal.adaptor.EclipseStorageHook.generateManifest(EclipseStorageHook.java:394)
    at org.eclipse.core.runtime.internal.adaptor.EclipseStorageHook.getGeneratedManifest(EclipseStorageHook.java:361)
    at org.eclipse.core.runtime.internal.adaptor.EclipseStorageHook.createCachedManifest(EclipseStorageHook.java:353)
    at org.eclipse.core.runtime.internal.adaptor.EclipseStorageHook.getManifest(EclipseStorageHook.java:458)
    at org.eclipse.osgi.internal.baseadaptor.BaseStorage.loadManifest(BaseStorage.java:251)
    at org.eclipse.osgi.internal.baseadaptor.BaseStorage.readStateData(BaseStorage.java:695)
    at org.eclipse.osgi.internal.baseadaptor.BaseStorage.getStateManager(BaseStorage.java:642)
    at org.eclipse.osgi.baseadaptor.BaseAdaptor.getPlatformAdmin(BaseAdaptor.java:385)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAdaptorHook.frameworkStart(EclipseAdaptorHook.java:78)
    at org.eclipse.osgi.baseadaptor.BaseAdaptor.frameworkStart(BaseAdaptor.java:260)
    at org.eclipse.osgi.framework.internal.core.SystemBundleActivator.start(SystemBundleActivator.java:55)
    at org.eclipse.osgi.framework.internal.core.BundleContextImpl$2.run(BundleContextImpl.java:999)
    at java.security.AccessController.doPrivileged(Native Method)
    at org.eclipse.osgi.framework.internal.core.BundleContextImpl.startActivator(BundleContextImpl.java:993)
    at org.eclipse.osgi.framework.internal.core.BundleContextImpl.start(BundleContextImpl.java:974)
    at org.eclipse.osgi.framework.internal.core.StartLevelManager.resumeBundles(StartLevelManager.java:611)
    at org.eclipse.osgi.framework.internal.core.StartLevelManager.incFWSL(StartLevelManager.java:497)
    at org.eclipse.osgi.framework.internal.core.StartLevelManager.doSetStartLevel(StartLevelManager.java:282)
    at org.eclipse.osgi.framework.internal.core.StartLevelManager.launch(StartLevelManager.java:250)
    at org.eclipse.osgi.framework.internal.core.SystemBundle.resume(SystemBundle.java:153)
    at org.eclipse.osgi.framework.internal.core.Framework.launch(Framework.java:588)
    at org.eclipse.osgi.framework.internal.core.OSGi.launch(OSGi.java:51)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.startup(EclipseStarter.java:289)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:172)
    at java.lang.reflect.Method.invoke(Native Method)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:508)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:447)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1173)
    at org.eclipse.equinox.launcher.Main.main(Main.java:1148)
2.出错环境：将myeclipse（eclipse+myeclipse插件）从A电脑拷到B电脑，运行，出错。
3.错误分析：看root exception，是java.lang.NoClassDefFoundError，这个异常出现的原因是：要么就没这个类，要么就是jdk无法去加载（有可能是环境变量path没配好，xp下的应用程序运行都会去读path环境变量里设的路径里的东西），我遇到的就是这个问题。既然类都加载不了，那么在osgi的过程中，jar包自然就不能被加载。所以主要原因找到。本质原因是oracle9i安装后会把他自己带的jre（jre1.3，版本太低）加到path的最前面，所以myeclipse启动是就会用oracle的jre，自然就会有问题。