为什么struts2-core-2.1.6.jar 需要和 commons-fileupload-1.2.1.jar同时使用

Question

我以前使用 struts2.1.4.jar 启动时不会报严重: Exception starting filter struts2
Unable to load bean: type: class:com.opensymphony.xwork2.ObjectFactory - bean - jar:file:/D:/Tomcat%206.0/webapps/struts2deam/WEB-INF/lib/struts2-core-2.1.6.jar!/struts-default.xml:29:72
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:395)
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:452)
at org.apache.struts2.dispatcher.FilterDispatcher.init(FilterDispatcher.java:205)
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:3709)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4356)
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:924)
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:887)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:492)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1147)
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:578)
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: Bean type class com.opensymphony.xwork2.ObjectFactory with the name xwork has already been loaded by bean - jar:file:/D:/Tomcat%206.0/webapps/struts2deam/WEB-INF/lib/struts2-core-2.0.14.jar!/struts-default.xml:30:72 - bean - jar:file:/D:/Tomcat%206.0/webapps/struts2deam/WEB-INF/lib/struts2-core-2.1.6.jar!/struts-default.xml:29:72
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.register(XmlConfigurationProvider.java:193)
... 33 more
2009-7-7 15:32:23 org.apache.catalina.core.StandardContext start
严重: Error filterStart而使用struts2.1.6.jar 
除了需要添加struts2-core-2.1.6.jar 同时也要添加 commons-fileupload-1.2.1.jar 
它的作用是什么？

Answer 1

fileupload
这个是支持文件操作方面的,如上传下载等
版本不监容当然会出现问题的了

Answer 2

struts2.1.4.jar以前的版本 添加五个必须的jar包就OK  commons-logging-版本.jar 
  freeer-版本.jar  
  ognl-版本.jar  
  struts2-core-版本.jar
  xwork-版本.jar但是 最先的struts2.1.6必须比以前多添加一个jar包  commons-fileupload-1.2.1虽然sturts2_blank中使用了commons-io-1.3.2.jar，但它也是要看情况的不是必须的