Use URL rewrite to save session data : Session « Servlets « Java

Use URL rewrite to save session data


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 {
    PrintWriter out = res.getWriter();

    out.println("<HEAD><TITLE>Current Shopping Cart Items</TITLE></HEAD>");

    // 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:<BR>");
    if (items == null) {
    } else {
      for (int i = 0; i < items.length; i++) {
        out.println("<LI>" + items[i]);

    // Ask if the user wants to add more items or check out.
    // Include the session ID in the action URL.
    out.println("<FORM ACTION=\"/servlet/ShoppingCart/" + sessionid + "\" METHOD=POST>");
    out.println("Would you like to<BR>");
    out.println("<INPUT TYPE=SUBMIT VALUE=\" Add More Items \">");
    out.println("<INPUT TYPE=SUBMIT VALUE=\" Check Out \">");

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


  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" };


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