Servlet sessions

Hi,

I'm following a tutorial I found and I'm having difficulty saving session information.

Here's the rundown, my code follows my signature.
http://localhost:8080/simpleweb/ParamServlet?param1=World&Param2=Hello
Gets the parameters, displays them, and saves them in the session.
Click on "Click here for target"

simpleweb/TargetServlet
Displays the session information saved in simpleweb/ParamServlet.

TargetServlet behaves as though there is no Session information, just displays this
Information in the session:

Session Exists!

Name: org.apache.catalina.ASYNC_SUPPORTED, Value: null
Done

All servlets appear to link fine so I don't think the problem is in web.xml. I remember to stop and restart Tomcat with each change.

Apache Tomcat 7.0.5 Server
javac -version = "javac 1.6.0_23"

Any help you provide would be greatly appreciated!

Thanks,

Lou

Here's the code
ParamServlet

package simpleweb;

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

public class ParamServlet extends HttpServlet {
 static final String CONTENT_TYPE = "text/html";
 // http://localhost:8080/simpleweb/ParamServlet?param1=World&Param2=Hello
 // Process the HTTP Get request.
 public void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 response.setContentType(CONTENT_TYPE);
 PrintWriter out = response.getWriter();
 out.println("<html>");
 out.println("<body>");
 // Create a session.
 HttpSession session = request.getSession(true);
 Enumeration e = request.getParameterNames();
 while (e.hasMoreElements()) {
 String param = (String) e.nextElement();
 String value = (String) request.getParameter(param);
 out.println("The parameter named " + param);
 out.println(" has a value of " + value);
 out.println("");
 session.setAttribute(param, value);
 }
 out.println(session); // test
 out.println("<a >");
 out.println("Click here for target</a>");
 out.println("</body>");
 out.println("</html>");
 }
 
 public void doPost(HttpServletRequest request, HttpServletResponse response) 
 throws ServletException, IOException {
 response.setContentType(CONTENT_TYPE);
 PrintWriter out = response.getWriter();
 out.println("<html>");
 out.println("<head><title>ParamServlet</title><head>");
 out.println("<body>");
 out.println("</body></html>");
 }
}

TargetServlet

package simpleweb;

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

public class TargetServlet extends HttpServlet {
 static final String CONTENT_TYPE = "text/html";
 
 // Process the HTTP Get request.
 public void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 response.setContentType(CONTENT_TYPE);
 PrintWriter out = response.getWriter();
 out.println("<html>");
 out.println("<body>");
 out.println("Information in the session:");
 // Get the session.
 HttpSession session = request.getSession(false);
 if (session == null) {
 out.println("Error! No session");
 return;
 }
 out.println("Session Exists!");
 Enumeration e = request.getAttributeNames();
 while (e.hasMoreElements()) {
 String name = (String) e.nextElement();
 String value = (String) session.getAttribute(name);
 out.print("Name: " + name + ", ");
 out.println("Value: " + value);
 out.println("");
 }
 out.println("Done</body>");
 out.println("</html>");
 }
 
 public void doPost(HttpServletRequest request, HttpServletResponse response) 
 throws ServletException, IOException {
 response.setContentType(CONTENT_TYPE);
 PrintWriter out = response.getWriter();
 out.println("<html>");
 out.println("<head><title>ParamServlet</title><head>");
 out.println("<body>");
 out.println("</body></html>");
 }
}

web.xml

why this code is there in TargetServlet, it doesn't getany request attributes/parameters i guess, from what i see.. so subsequently, control doesn't go inside the while loop..

When you are invoking Target Servlet, there are no parameters in request. All parameters are present in HTTPSession. So get your parameters from session ( not from request)

Just replace

with

in Target Servlet doGet() and you will get your desired result as shown below.

Information in the session:

Session Exists!

Name: Param2, Value: Hello
Name: param1, Value: World
Done

~ abhay

Thank you Abhay!

That was the problem. I copied ParamServlet as TargetServlet and made modifications, but I missed that one.

Spent a long time looking for it. I think the difference between Request and Session is burnt into memory now, and I'll quickly know what to look for (hopefully) if I see this again!