Struts2.x异常:Unable to load configuration..../WEB-INF/lib/struts2-convention-plugin-2.1.6.jar!/struts

Struts 2.x异常:Unable to load configuration..../WEB-INF/lib/struts2-convention-plugin-2.1.6.jar!/struts-plugin.xml:30:119

在开发Struts 2.x项目时，如果将struts-2.1.6-all.zip中lib文件夹中的jar包一股脑的导入到项目工程中就会出现如下异常，我觉得这是Struts2的一大bug，更确切的说是设计缺陷。

2009-2-18 15:02:09 com.opensymphony.xwork2.util.logging.commons.CommonsLogger info
信息: Parsing configuration file [struts-default.xml]
2009-2-18 15:02:10 com.opensymphony.xwork2.util.logging.commons.CommonsLogger info
信息: Parsing configuration file [struts-plugin.xml]
2009-2-18 15:02:10 org.apache.catalina.core.StandardContext filterStart
严重: Exception starting filter struts2
Unable to load configuration. - bean - jar:file:/C:/Tomcat6/webapps/EJBBookStoreWebModule/WEB-INF/lib/struts2-convention-plugin-2.1.6.jar!/struts-plugin.xml:30:119
 at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:58)
 at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:360)
 at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:403)
 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.(ApplicationFilterConfig.java:108)
 at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3709)
 at org.apache.catalina.core.StandardContext.start(StandardContext.java:4363)
 at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791)
 at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771)
 at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:525)
 at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:926)
 at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:889)
 at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:492)
 at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1217)
 at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:293)
 at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
 at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1337)
 at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1601)
 at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610)
 at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1590)
 at java.lang.Thread.run(Thread.java:595)
Caused by: Unable to load bean: type:com.opensymphony.xwork2.UnknownHandler class:org.apache.struts2.convention.ConventionUnknownHandler - bean - jar:file:/C:/Tomcat6/webapps/EJBBookStoreWebModule/WEB-INF/lib/struts2-convention-plugin-2.1.6.jar!/struts-plugin.xml:30:119
 at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.register(XmlConfigurationProvider.java:222)
 at org.apache.struts2.config.StrutsXmlConfigurationProvider.register(StrutsXmlConfigurationProvider.java:101)
 at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:165)
 at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:55)
 ... 22 more
Caused by: Bean type interface com.opensymphony.xwork2.UnknownHandler with the name default has already been loaded by bean - jar:file:/C:/Tomcat6/webapps/EJBBookStoreWebModule/WEB-INF/lib/struts2-codebehind-plugin-2.1.6.jar!/struts-plugin.xml:29:122 - bean - jar:file:/C:/Tomcat6/webapps/EJBBookStoreWebModule/WEB-INF/lib/struts2-convention-plugin-2.1.6.jar!/struts-plugin.xml:30:119
 at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.register(XmlConfigurationProvider.java:206)
 ... 25 more
2009-2-18 15:02:10 org.apache.catalina.core.StandardContext start
严重: Error filterStart
2009-2-18 15:02:10 org.apache.catalina.core.StandardContext start
严重: Context [/EJBBookStoreWebModule] startup failed due to previous errors
解决方案 ：

将struts-2.1.6-all.zip中apps文件夹中struts2-blank-2.1.6.war文件解压。进入struts2-blank-2.1.6/WEB-INF/lib，只将该文件夹下的9个jar包导入到项目工程中即可，其余的包如果没有用到切不可轻易导入。