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Pre- Existing Session

                         

In this example we are going to find out whether the session is pre-existing or not. 

Consider a situation where servlet want to use only a existing session. It is not always a good idea to create a new session. To perform this work we have one overloaded method getSession(boolean) of the request object. If we don't want to create a new session then we should use getSession(false)

In the example below we have used the method getSession(false) which will test whether the session is null or not. If there will be no session then the new session will be created by the method getSession().

The code of the program is given below:

PreExistingSessionServlet.java

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class PreExistingSessionServlet extends HttpServlet{
  protected void doGet(HttpServletRequest request, HttpServletResponse response)
                             throws ServletException, IOException {
    response.setContentType("text/html");
    PrintWriter pw = response.getWriter();
    pw.println("Testing The Session : ");
    HttpSession session = request.getSession(false);
    if(session==null){
      pw.println("There is no session");
      pw.println("Can we create a session for you. Creating.........");
      session = request.getSession();
    }
    else{
      pw.println("Session already exists");
    }
  }
}

web.xml file for this program:

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app
 PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd">

<web-app>
 <servlet>
 <servlet-name>Zulfiqar</servlet-name>
 <servlet-class>PreExistingSessionServlet</servlet-class>
 </servlet>
 <servlet-mapping>
 <servlet-name>Zulfiqar</servlet-name>
 <url-pattern>/PreExistingSessionServlet</url-pattern>
 </servlet-mapping>
</web-app>

The output of the program is given below:

Download this example:

                         

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