Struts2 global result throwing StackOverflowError on result type chain/tiles

Question

below are my interceptors & global-results as defined in struts.xml

 <package name="auth_basic" extends="struts-default,tiles-default">
<interceptors>
        <interceptor name="nlogin" class="interceptors.LoginInterceptor"/>
        <interceptor-stack name="loginStack">
            <interceptor-ref name="nlogin"/>
            <interceptor-ref name="defaultStack"/>
        </interceptor-stack>
    </interceptors>
    <default-interceptor-ref name="loginStack"/>
    <global-results>
        <result name="login" type="redirectAction">gotostart</result>
        <result name="input" type="redirectAction">gotostart</result>
    </global-results>
.
.
.
</package>

The above configuration works fine, but when I use result chain instead of redirectAction it gives java.lang.StackOverflowError

Also when I use tiles instead of chain, then also it throws java.lang.StackOverflowError

Can I not use action-chaining in global-results ?

Below is my interceptor code. Also, I would like to EMPHASIZE on the point that result type redirectAction is working fine, only tiles & chain are creating problems.

public String intercept(ActionInvocation ai) throws Exception {
    try {
        if (ai.getInvocationContext().getSession().get("user") == null) {
            System.out.println("Session Expired/Invalid");
            Object action = ai.getAction();
            if (action instanceof ValidationAware) {
                ((ValidationAware) action).addActionError("Unauthorized access. Please Login first");
            }
            return "login";
        }
        return ai.invoke();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return ai.invoke();
}

edited to include more code from struts.xml

 <package name="default" extends="struts-default,tiles-default,json-default">
    <default-action-ref name="gotostart"/>
    <global-results>
        <result name="input" type="tiles">tiles-home</result>
    </global-results>
<action name="gotostart" class="actions.IndexAction" method="start">
        <result name="success" type="tiles">tiles-home</result>
        <result name="input" type="tiles">tiles-home</result>
    </action>
</package>

Answer 1

Ok, got it.

If not logged in, you are returning an global result, login, that is a chain result type, then a call to another action.

The login result type is under the same Interceptor Stack containing the nLogin Interceptor.

This means that when you try to chain your login result, you pass AGAIN inside your nLogin Interceptor, checking again if user is null, and returning login result, in and endless loop.

You can:

return a JSP instead of chaining to another Action, like this:

<result name="login">myLogin.jsp</result>

or move your global result login outside your custom Interceptor Stack scope (putting it under the default stack in a parent package, for example), like this:

<struts>
   <package name="defaultPackage" extends="struts-default" >

      <default-interceptor-ref name="defaultStack"/>

      <global-results>
         <result name="login" type="chain">
            <param name="actionName">myLoginAction</param>
         </result>
      </global-results>

   </package>

   <package name="myLoginProtectedPackage" extends="defaultPackage">

      <interceptors>
         <interceptor name="nlogin" class="interceptors.LoginInterceptor"/>
         <interceptor-stack name="loginStack">
            <interceptor-ref name="nlogin"/>
            <interceptor-ref name="defaultStack"/>
         </interceptor-stack>
      </interceptors>

      <default-interceptor-ref name="loginStack"/>

      <global-results>
        <result name="input" type="chain">
            <param name="actionName">myLoginAction</param>
        </result>
      </global-results>    

      <action name="myLoginAction" class="...">
         <result>myLogin.jsp</result>             
      </action>

   </package>
</struts>

Don't ask me why with redirectAction works... it should be the same, but probably is due to their different behavior.

Please note that, according to the guide,

As a rule, Action Chaining is not recommended. First explore other options, such as the Redirect After Post technique.