struts2配置错误 There is no Action mapped for namespace [/] and action name [] associated with context

今天在使用struts2的时候遇到这个问题。
Struts has detected an unhandled exception:

Messages:

There is no Action mapped for namespace [/] and action name [] associated with context path [/ssm1].

这个时候的struts.xml文件如下：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD StrutsConfiguration 2.3//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
	<constant name="struts.enable.DynamicMethodInvocation" value="false"/>
	<constant name="struts.devMode" value="true"/>
	<constant name="struts.objectFactory" value="spring" />
    <package name="default" namespace="/" extends="struts-default">
        	<!-- 注意：这里的class -->
        	<action name="student_*" class="studentAction" method="{1}">
        			<result name="add_success">/add_success.jsp</result>
        	</action>
    </package>
</struts>

解决方案：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
	<constant name="struts.enable.DynamicMethodInvocation" value="false"/>
	<constant name="struts.devMode" value="true"/>
	<constant name="struts.objectFactory" value="spring" />
    <package name="default" namespace="/" extends="<span style="background-color: rgb(255, 255, 0);">struts-default</span>">
        	<!-- 注意：这里的class -->
        	<action name="student_*" class="studentAction" method="{1}">
        			<result name="add_success">/add_success.jsp</result>
        	</action>
    </package>
</struts>

所以，多注意一下struts.xml 中的配置项，关键的细节点，一定要处理好。