Session Check Interceptor

There must be some way to check that the current session is valid or invalid. This can be done using interceptors in struts in a very easy way.
Here I am giving an example how to resolve this.

First of all we will make an interceptor named SessionCheck.java.

package com.demo.interceptors;

import java.util.Collections;
import java.util.Map;

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.ActionProxy;
import com.opensymphony.xwork2.config.entities.ResultConfig;
import com.opensymphony.xwork2.interceptor.Interceptor;

public class SessionCheck implements Interceptor {

public void init() {
}

public void destroy() {
}

public String intercept(ActionInvocation invocation) throws Exception {
ActionProxy proxy;
proxy = invocation.getProxy();
Map session = ActionContext.getContext().getSession();
Map results = proxy.getConfig().getResults();
/*
* We are checking that the user
* that is set at login time is null or not
*/
if (session.get("user") != null) {

return invocation.invoke();
} else {
/* Here we are passing the result to an
* invalid page by specifying its location
*/
ResultConfig rc = new ResultConfig("invalid",
"org.apache.struts2.views.freemarker.FreemarkerResult",
Collections.singletonMap("location",
"/com/demo/interceptors/invalid.jsp"));
results.put("invalid", rc);

return "invalid";
}

}
}

Now in struts.xml put the following code

<?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>
-----
---

<interceptors>

<interceptor name="SessionCheck"
class="com.demo.interceptors.SessionCheck" />
</interceptors>
<!—- We are using this because we want it to apply for each and every action -->
<default-interceptor-ref name="SessionCheck"/>


---
---
</struts>