访问struts2的action页面出现白板问题

<bean id="authenticationInterceptor" class="com.cosl.util.interceptor.AuthenticationInterceptor"></bean><!--权限拦截器 -->

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
"-//Apache Software  Foundation//DTD Struts Configuration 2.1//EN"
"http://struts.apache.org/dtds/struts-2.1.dtd">

<struts>
<package name="struts-my" extends="json-default">

<interceptors>
<!-- 判断是否登录 和 是否有访问权限 -->
<interceptor name="auth" class="authenticationInterceptor"/><!-- 这是com.cosl.util.interceptor.AuthenticationInterceptor的拦截器，在applicationContext.xml文件里实例化了 -->
<interceptor-stack name="myStack">
<interceptor-ref name="auth"></interceptor-ref>
<interceptor-ref name="defaultStack"></interceptor-ref>
</interceptor-stack>
</interceptors>
<default-interceptor-ref name="myStack"></default-interceptor-ref>
<default-action-ref name="notFound"/> 
<global-results>
<result name="noLogin" type="redirect">/pages/Developer/loginJsp</result>
<result name="noPower" type="redirect">/no_power.jsp</result>
</global-results>
<action name="notFound" class="com.cosl.util.CommonAction" method="notFound">  
            <result name="success">/not_found.jsp</result>  
        </action>  
</package>
</struts>

<package name="Diaocha" extends="struts-my" namespace="/pages/Diaocha">
    
                <action name="diaochaJsp" class="com.cosl.action.DiaochaAction" method="diaochaJsp">
                <interceptor-ref name="defaultStack"/><!-- 这儿让我调试了4个小时，直接访问action没出任何结果，因为被interceptor拦截了 -->
            <result name="diaochaJsp">/admin/editPasswordJsp.jsp</result>
        </action>
        
        
        </package>

public class AuthenticationInterceptor extends AbstractInterceptor {

    
    
    @Override
    public String intercept(ActionInvocation invocation) throws Exception {
        // TODO Auto-generated method stub
        Map map=invocation.getInvocationContext().getSession();
        if(map.get("user")!=null)
        {
            //return "noLogin";
             return invocation.invoke();  
        }else{
            //获得登录用户的权限
        }
        return null;
    }

}