第一种报错：
严重: Exception starting filter struts2
Unable to load configuration. - action - file:/E:/apache-tomcat-8.0.37/webapps/20161102-struts2-3/WEB-INF/classes/struts.xml:11:73
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:504)
at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:74)
at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:57)
at org.apache.catalina.core.ApplicationFilterConfig.initFilter(ApplicationFilterConfig.java:279)
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:260)
at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:105)
at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4700)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5340)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:725)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717)
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:587)
at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1798)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: Unable to load configuration. - action - file:/E:/apache-tomcat-8.0.37/webapps/20161102-struts2-3/WEB-INF/classes/struts.xml:11:73
at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:70)
at org.apache.struts2.dispatcher.Dispatcher.getContainer(Dispatcher.java:978)
at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:446)
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:490)
... 18 more
Caused by: Action class [com.tt.struts2.action.TestActionContextAction] not found - action - file:/E:/apache-tomcat-8.0.37/webapps/20161102-struts2-3/WEB-INF/classes/struts.xml:11:73
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.verifyAction(XmlConfigurationProvider.java:486)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addAction(XmlConfigurationProvider.java:429)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addPackage(XmlConfigurationProvider.java:556)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadPackages(XmlConfigurationProvider.java:295)
at org.apache.struts2.config.StrutsXmlConfigurationProvider.loadPackages(StrutsXmlConfigurationProvider.java:112)
at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:264)
at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:67)
... 21 more
原因分析：最后一行caused by报的错Action class [com.tt.struts2.action.TestActionContextAction] not found，去工程的目录build->classes文件夹下查看，确实没看到TestActionContextAction的class文件。但是代码又是对的，没道理不存在TestActionContextAction的class文件。
解决办法：检查代码实在找不出问题，lib包也导的是正确的。最后无奈重启电脑，然后工程的目录build->classes文件夹下就有了TestActionContextAction的class文件。问题就解决了。真是奇葩啊。。。
第二种报错：
Dispatcher initialization failed
十一月 07, 2016 10:43:53 上午 org.apache.catalina.core.StandardContext filterStart
严重: Exception starting filter struts2
Unable to load configuration. - action - file:/E:/apache-tomcat-8.0.37/webapps/20161102-struts2-3/WEB-INF/classes/struts.xml:64:78
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:504)
at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:74)
at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:57)
at org.apache.catalina.core.ApplicationFilterConfig.initFilter(ApplicationFilterConfig.java:279)
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:260)
at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:105)
at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4700)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5340)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:725)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717)
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:587)
at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1798)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: Unable to load configuration. - action - file:/E:/apache-tomcat-8.0.37/webapps/20161102-struts2-3/WEB-INF/classes/struts.xml:64:78
at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:70)
at org.apache.struts2.dispatcher.Dispatcher.getContainer(Dispatcher.java:978)
at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:446)
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:490)
... 18 more
Caused by: Error building results for action testAction in namespace /taotian - action - file:/E:/apache-tomcat-8.0.37/webapps/20161102-struts2-3/WEB-INF/classes/struts.xml:64:78
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addAction(XmlConfigurationProvider.java:441)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addPackage(XmlConfigurationProvider.java:556)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadPackages(XmlConfigurationProvider.java:295)
at org.apache.struts2.config.StrutsXmlConfigurationProvider.loadPackages(StrutsXmlConfigurationProvider.java:112)
at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:264)
at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:67)
... 21 more
Caused by: No result type specified for result named 'success', perhaps the parent package does not specify the result type? - result - file:/E:/apache-tomcat-8.0.37/webapps/20161102-struts2-3/WEB-INF/classes/struts.xml:65:26
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.buildResults(XmlConfigurationProvider.java:716)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addAction(XmlConfigurationProvider.java:439)
... 26 more
原因分析：最后一个caused by报错里No result type specified for result named 'success', perhaps the parent package does not specify the result type?它说父包里没有定义"success"的result。检查struts.xml文件，看到第二个package:testPackage的定义里没有继承struts-default包，而result默认是"success"，所以testPackage里无法使用"success"的result。
解决办法：让testPackage继承struts-default包，那么testPackage就可以使用"success"的result了。
