引用struts2後無法啟動application server

2010/10/14 下午 04:45:03 org.apache.catalina.core.StandardContext filterStart
嚴重的: Exception starting filter struts2
Unable to load bean: type:com.opensymphony.xwork2.util.ValueStackFactory class:com.opensymphony.xwork2.ognl.OgnlValueStackFactory - bean - jar:file:/D:/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp1/wtpwebapps/epza/WEB-INF/lib/struts2-core-2.1.8.1.jar!/struts-default.xml:70:140
    at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:431)
    at org.apache.struts2.dispatcher.FilterDispatcher.init(FilterDispatcher.java:190)
    at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:275)
    at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:397)
    at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:108)
    at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3800)
    at org.apache.catalina.core.StandardContext.start(StandardContext.java:4450)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardHost.start(StandardHost.java:722)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
    at org.apache.catalina.core.StandardService.start(StandardService.java:516)
    at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:583)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
Caused by: Unable to load bean: type:com.opensymphony.xwork2.util.ValueStackFactory class:com.opensymphony.xwork2.ognl.OgnlValueStackFactory - bean - jar:file:/D:/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp1/wtpwebapps/epza/WEB-INF/lib/struts2-core-2.1.8.1.jar!/struts-default.xml:70:140
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.register(XmlConfigurationProvider.java:208)
    at org.apache.struts2.config.StrutsXmlConfigurationProvider.register(StrutsXmlConfigurationProvider.java:101)
    at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reload(DefaultConfiguration.java:131)
    at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:52)
    at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:374)
    at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:418)
    ... 19 more
Caused by: java.lang.IncompatibleClassChangeError: Implementing class
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1850)
    at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:890)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1354)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233)
    at com.opensymphony.xwork2.util.ClassLoaderUtil.loadClass(ClassLoaderUtil.java:139)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.register(XmlConfigurationProvider.java:180)
    ... 24 more

由以上訊息可以看出跟載入不相容的class有關，如果你不小心使用了兩個不同版本struts2的jar就有可能造成這個問題。
錯誤訊息的另一個關鍵是xwork，代表跟xwork有關，所以問題是使用了兩個版本的xwork，我的情形是xwork-core-2.1.6.jar, xwork-2.0.7.jar同時存在，因為我目的是要使用struts 2.1.x的版本，因此，刪除xwork-2.0.7.jar即可正常啟動。