Get and Set Session Variables in a Servlet

Do you need help with your Java programming?

Click here for instant help with your Java code.

This code example shows how to set and get variables stored in a session. To get a reference to the session object we call the getSession() method of the HttpServletRequest object.
We send the argument true to the method to tell it to create the session if it doesn't exist.
Then we try to get the session variable 'VisitCounter' from the session by calling the method getAttribute().
It's supposed to be stored as an Integer object, so we cast it to an Integer directly.
If the parameter is null, we create a new Integer object with the value of one (1) and add it to the session, else we add one to the object retrieved from the session and write it back to the session again. When writing a variable to the session the method setAttribute() is used.
Then we print out the value of the session parameter, which tells how many times this page has been displayed during this particular session.

import java.io.*;

import javax.servlet.*;
import javax.servlet.http.*;

/**
* Example Servlet
* @author www.javadb.com
*/
public class ExampleServlet extends HttpServlet {

    /** Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
     * @param request servlet request
     * @param response servlet response
     */
    protected void service(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();

        printPageStart(out);

        //Obtain the session object, create a new session if doesn't exist
        HttpSession session = request.getSession(true);

        //Check if our session variable is set, if so, get the session variable value
        //which is an Integer object, and add one to the value.
        //If the value is not set, create an Integer object with the default value 1.
        //Add the variable to the session overwriting any possible present values.
        Integer param = (Integer) session.getAttribute("MySessionVariable");
        if (param != null) {

            session.setAttribute("MySessionVariable", new Integer(param.intValue() + 1));
            param = (Integer) session.getAttribute("MySessionVariable");

        } else {

            param = new Integer(1);
            session.setAttribute("MySessionVariable", param);

        }

        out.println("You have displayed this page <b>" + param.intValue() + "</b> times this session.<br/><br/>");
        out.println("Hit the browsers refresh button.");

        printPageEnd(out);
    }

    /** Prints out the start of the html page
     * @param out the PrintWriter object
     */
    private void printPageStart(PrintWriter out) {

        out.println("<html>");
        out.println("<head>");
        out.println("<title>Example Servlet of how to store and retrieve session variables</title>");
        out.println("</head>");
        out.println("<body>");

    }

    /** Prints out the end of the html page
     * @param out the PrintWriter object
     */
    private void printPageEnd(PrintWriter out) {

        out.println("</body>");
        out.println("</html>");
        out.close();
    }
}

This is what the text will look like if you hit the refresh button a few times:

You have displayed this page 16 times this session.

Hit the browsers refresh button.

Do you know your Java?
Take a Ten-Question-Java-Quiz!

Search for code examples on this site

Need help with your Java code? It's secure and confidential.

This is how it works:

Send a detailed description of what you need help with, the more details the better. Also provide a deadline for when it has to be finished. More time means better chance of putting your request into the schedule.

If the request is serious you will shortly receive an email with the price, to which you have to respond if you accept.

Once you have accepted, the work will begin on developing your code by an experienced Java developer. When the code is finished a link to a secure payment will be sent to you.

The source code is then sent to you once the payment is completed.

IMPORTANT! The request needs to be very detailed, else it may be ignored.

Write your detailed request here:

E-mail address: