如果spring注入， service和dao为空，首先检查相关配置，同时确认 struts2-spring-plugin.jar的存在。
严重: Exception starting filter struts-invoke
Unable
to load configuration. - bean -
jar:file:/D:/sshtest/.metadata/.me_tcat/webapps/ssh/WEB-INF/lib/struts2-spring-plugin-2.1.8.1.jar!/struts-plugin.xml:29:132
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.ng.InitOperations.initDispatcher(InitOperations.java:69)
at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:48)
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:3693)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4340)
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:920)
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:883)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:492)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1138)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:719)
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:566)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
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.ObjectFactory
class:org.apache.struts2.spring.StrutsSpringObjectFactory - bean -
jar:file:/D:/sshtest/.metadata/.me_tcat/webapps/ssh/WEB-INF/lib/struts2-spring-plugin-2.1.8.1.jar!/struts-plugin.xml:29:132
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)
... 31 more
Caused by: java.lang.NoClassDefFoundError: com/opensymphony/xwork2/util/classloader/ReloadingClassLoader
at java.lang.Class.getDeclaredConstructors0(Native Method)
at java.lang.Class.privateGetDeclaredConstructors(Class.java:2389)
at java.lang.Class.getDeclaredConstructors(Class.java:1836)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.register(XmlConfigurationProvider.java:212)
... 34 more
Caused by: java.lang.ClassNotFoundException: com.opensymphony.xwork2.util.classloader.ReloadingClassLoader
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1358)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1204)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
... 38 more
2011-8-5 21:32:21 org.apache.catalina.core.StandardContext start
严重: Error filterStart
2011-8-5 21:32:21 org.apache.catalina.core.StandardContext start
严重: Context [/ssh] startup failed due to previous errors
2011-8-5 21:32:21 org.apache.catalina.core.ApplicationContext log
信息: Closing Spring root WebApplicationContext
2011-8-5 21:32:22 org.apache.coyote.http11.Http11Protocol start
信息: Starting Coyote HTTP/1.1 on http-8080
2011-8-5 21:32:22 org.apache.jk.common.ChannelSocket init
信息: JK: ajp13 listening on /0.0.0.0:8009
2011-8-5 21:32:22 org.apache.jk.server.JkMain start
信息: Jk running ID=0 time=0/16 config=null
2011-8-5 21:32:22 org.apache.catalina.startup.Catalina start
信息: Server startup in 8807 ms
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以上由 Struts 2 必备JAR 包导入错误，引发以上异常，现贴出 Struts 2 必备JAR 包对照表，方便各位JAVA友。
struts-2.1.6-lib 必备JAR包 (共8个)：
commons-fileupload-1.2.1.jar
commons-io-1.3.2.jar
commons-logging-1.0.4.jar
freemarker-2.3.13.jar
ognl-2.6.11.jar
struts2-core-2.1.6.jar
struts2-spring-plugin-2.1.6.jar
// 如果此包用成 struts2-spring-plugin-2.1.8.1.jar 就会产生上面的异常，切记！！！
xwork-2.1.2.jar
struts-2.1.8-lib 必备JAR包(共8个)：
commons-fileupload-1.2.1.jar
commons-io-1.3.2.jar
commons-logging-1.0.4.jar
freemarker-2.3.15.jar
ognl-2.7.3.jar
struts2-core-2.1.8.1.jar
struts2-spring-plugin-2.1.8.1.jar
xwork-core-2.1.6.jar
Struts 2 JAR 包下载官方网站：http://struts.apache.org/2.x/ 或 http://archive.apache.org/