How to Use URL rewrite to save session data in java

import java.io.IOException;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ShoppingCartViewerRewrite extends HttpServlet {

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

out.println("");
out.println("");

// Get the current session ID, or generate one if necessary
String sessionid = req.getPathInfo();
if (sessionid == null) {
sessionid = generateSessionId();
}

// Cart items are associated with the session ID
String[] items = getItemsFromCart(sessionid);

// Print the current cart items.
out.println("You currently have the following items in your cart:
");
if (items == null) {
out.println("None");
} else {
out.println("

");
for (int i = 0; i < items.length; i++) {
out.println("
• " + items[i]);
  }
  out.println("

");
}

// Ask if the user wants to add more items or check out.
// Include the session ID in the action URL.
out.println("

");
out.println("Would you like to
");
out.println("");
out.println("");
out.println("

");

// Offer a help page. Include the session ID in the URL.
out.println("For help, click + "?topic=ShoppingCartViewerRewrite\">here");

out.println("");
}

private static String generateSessionId() throws UnsupportedEncodingException {
String uid = new java.rmi.server.UID().toString(); // guaranteed unique
return URLEncoder.encode(uid, "UTF-8"); // encode any special chars
}

private static String[] getItemsFromCart(String sessionid) {
return new String[] { "a", "b" };
}
}