一个苦恼的404异常_Java Web开发

一个苦恼的404错误！
报错：There is no Action mapped for namespace [/] and action name [submit] associated with context path [/ZHONGWEIMAP].

这里是编译器报错,删了一部分：
严重: Exception occurred during processing request: null
java.lang.NullPointerException
at com.zhongwei.action.SystemAction.execute(SystemAction.java:13)
at java.lang.Thread.run(Thread.java:619)
2015-4-25 20:39:01 com.opensymphony.xwork2.util.logging.commons.CommonsLogger warn
警告: Could not find action or result
There is no Action mapped for namespace [/] and action name [submit] associated with context path [/ZHONGWEIMAP]. - [unknown location]
at com.opensymphony.xwork2.DefaultActionProxy.prepare(DefaultActionProxy.java:185)
at java.lang.Thread.run(Thread.java:619)
2015-4-25 20:39:01 com.opensymphony.xwork2.util.logging.commons.CommonsLogger error
严重: Exception occurred during processing request: There is no Action mapped for namespace [/] and action name [submit] associated with context path [/ZHONGWEIMAP].
There is no Action mapped for namespace [/] and action name [submit] associated with context path [/ZHONGWEIMAP]. - [unknown location]
at com.opensymphony.xwork2.DefaultActionProxy.prepare(DefaultActionProxy.java:185)
at org.apache.struts2.impl.StrutsActionProxy.prepare(StrutsActionProxy.java:63)
at java.lang.Thread.run(Thread.java:619)

这里是struts.xml文件：
<package name="default" namespace="/" extends="struts-default">
     <global-results>
         <result name="login">/login.jsp</result>
     </global-results>

      <action name="submit" class="com.zhongwei.action.SubmitAction">
            <result name="success">
                /submitSuccess.jsp
            </result>
        </action>

        <action name="login" class="com.zhongwei.action.LoginAction">
            <result name="success">
                /main.jsp
            </result>
            <result name="fail">
                /login.jsp
            </result>
        </action>
</package>

这里是web.xml文件：
<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_9"
         version="2.4"
         xmlns="http://java.sun.com/xml/ns/j2ee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
         http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <display-name>Struts Blank</display-name>

   <filter>
        <filter-name>Set Character Encoding</filter-name>
        <filter-class>com.zhongwei.filter.SetCharacterEncodingFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>Set Character Encoding</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <filter>
        <filter-name>struts2</filter-name>
        <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>struts2</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

这里是form标签
<form action="submit" method="post" name="submit">

补充信息：如果将form标签的action属性改为action="login" ，可以成功跳转到登陆界面。

这里是文件目录

------解决思路----------------------
java.lang.NullPointerException
at com.zhongwei.action.SystemAction.execute(SystemAction.java:13)

把你的SystemAction文件贴一下。。。
------解决思路----------------------
你这是空指针异常，你debug一下就知道了