Servlets - Session Tracking

HTTP is a "stateless" protocol meaning when client retrieves a Web page, client opens a new separate connection to Web server and it does not keep any record of previous client request.

The HttpSession Object

The servlet container have interface for creating session between HTTP client and HTTP server. The session persists for specified time period across more than one connection or page request from user.

We can access HttpSession object by calling public method getSession() of HttpServletRequest as below:

HttpSession session = request.getSession();

Below are the few methods used for accessing the session objects :

Below is the example of managing session in servlets.

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

public class SessionExample extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws IOException, ServletException
    {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();

        HttpSession session = request.getSession(true);

        // print session info

        Date created = new Date(session.getCreationTime());
        Date accessed = new Date(session.getLastAccessedTime());
        out.println("ID " + session.getId());
        out.println("Created: " + created);
        out.println("Last Accessed: " + accessed);
    }
}

Here is what we get:

Deleting Session Data

The Session data can be removed as shown below:

• Remove particular attribute: public void removeAttribute(String name) method used to remove session.
• Delete whole session: public void invalidate() method can be used to delete entire session.
• Setting Session timeout: public void setMaxInactiveInterval(int interval) method will set timeout to session individually.
• web.xml Configuration: session time out can be set in web.xml as follows.
  

    <session-config>
      <session-timeout>15</session-timeout>
    </session-config>
  
  
  
  

In the next part of this quick introduction guide we will explore how to connect to a database.