Null Pointer Exception After calling Execute And Wait Interceptor

[Aravind Sivaramakrishnan]

Hi ,
Iam beginner in Struts2,
iam having query on Execute and wait Interceptor ,

my code flow is like this

Login->Wait Interceptor->Menu/Fail.jsp

I added Interceptor in Struts.xml

   
     <action name="doLogin" class="validatorlogin.Login">
            <interceptor-ref name="completeStack" />
            <interceptor-ref name="execAndWait" />                  
            <result name="wait">Wait.jsp</result>
            <result name="success">menudemo.jsp</result>
            <result name="error">Fail.jsp</result>
        </action>

 

When i run the project,
After Submitting Login.jsp ,Wait.jsp is rendered after that it throws Null pointer Exception instead of Menu.jsp

I went through Forums i find a similar query,but i dont understand the reason for this,

http://www.coderanch.com/t/433155/Struts/Application-Frameworks/with-execAndWait-interceptor


With reference to http://struts.apache.org/2.0.6/docs/execute-and-wait-interceptor.html

i tried adding delay before the wait page

   
  <interceptor-ref name="execAndWait">
        <param name="delay">1000<param>
        <param name="delaySleepInterval">50<param>
    <interceptor-ref>
 

Could any one please help me out ,
Thanks in advance,
Arvin