Session Tracking Example using Servlets
By Ramakrishna on Sep 8, 2008 in Session Tutorials
Sessions in Servlets
The following examples show the newer session tracking API in use within Servlets.
The first time a user runs the “Barman” servlet, it sets up a session for him and prompts for his name. On subsequent visits, it addresses him by name straight away, and also keeps a tally of how many times he’s visited.
The “Landlord” servlet does the same as the Barman, but in addition it maintains a static vector of sessions so that it can (and does ; – ) ) report on everyone in the bar and how much they’ve had to drink.
Note – “Barman” keeps the users apart, which is typically what you would do with a shopping cart … “Landlord” provides a management information service too ….
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Barman.java
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import java.io.*;
import java.text.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
/**
* Simple Session Tracking
*/
public class Barman extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException
{
HttpSession session = request.getSession(true);
Integer count = (Integer)session.getAttribute(“mycounter”);
response.setContentType(“text/html”);
PrintWriter out = response.getWriter();
out.println(” < html > “);
out.println(” < body bgcolor=\"white\" > “);
if (count == null) {
count = new Integer(0);
out.print(” < h1 >Welcome. Please enter your name< / h1 >“);
out.print(” < form action=/nan/servlet/Barman > “);
out.print(” < input name=whoyouare > “);
out.print(” < / form > “);
} else {
String wanted = request.getParameter(“whoyouare”);
if (wanted != null) {
session.setAttribute(“who”,wanted);
} else {
wanted = (String)session.getAttribute(“who”);
}
count = new Integer(count.intValue() + 1);
out.print(” < h1 > Welcome back “+wanted+”< / h1 > “);
out.println(“This is your visit no. “+count+”< BR >“);
}
session.setAttribute(“mycounter”,count);
out.println(” < / body > “);
out.println(” < / html > “);
}
}
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Landlord.java
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import java.io.*;
import java.text.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
/**
* Simple Session Tracking
* Also reports on all users
*/
public class Landlord extends HttpServlet {
public static Vector People;
public void init(ServletConfig cc) throws ServletException {
super.init(cc);
People = new Vector();
}
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException
{
HttpSession session = request.getSession(true);
Integer count = (Integer)session.getAttribute(“mycounter”);
response.setContentType(“text/html”);
PrintWriter out = response.getWriter();
out.println(” < html > “);
out.println(” < body bgcolor=\"white\" > “);
if (count == null) {
count = new Integer(0);
out.print(“< h1 >Welcome. Please enter your name< / h1 >“);
out.print(” < form action=/nan/servlet/Landlord > “);
out.print(” < input name=whoyouare > “);
out.print(” < / form > “);
People.addElement(session);
} else {
String wanted = request.getParameter(“whoyouare”);
if (wanted != null) {
session.setAttribute(“who”,wanted);
} else {
wanted = (String)session.getAttribute(“who”);
}
count = new Integer(count.intValue() + 1);
out.print(” < h 1 >Welcome back “+wanted+”< / h1 > “);
out.println(“This is your visit no. “+count+”< BR >“);
out.println(“< BR >< H2 >Those here present …< / h2 >“);
for (int i=0; i
String ere = (String)present.getAttribute("who");
out.print(ere+ " is here and has drunk ");
int ii = ((Integer)present.getAttribute("mycounter")).intValue();
out.print("" + ii + " previously< BR >“);
}
}
session.setAttribute(“mycounter”,count);
out.println(” < /body > “);
out.println(” < / html > “);
}
}
