使用cookie保存会话数据

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  1. import java.io.IOException;
  2. import java.io.PrintWriter;
  3. import java.io.UnsupportedEncodingException;
  4. import java.net.URLEncoder;
  5.  
  6. import javax.servlet.ServletException;
  7. import javax.servlet.http.Cookie;
  8. import javax.servlet.http.HttpServlet;
  9. import javax.servlet.http.HttpServletRequest;
  10. import javax.servlet.http.HttpServletResponse;
  11.  
  12. public class ShoppingCartViewerCookie extends HttpServlet {
  13.  
  14.   public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException,
  15.       IOException {
  16.     res.setContentType("text/html");
  17.     PrintWriter out = res.getWriter();
  18.  
  19.     String sessionid = null;
  20.     Cookie[] cookies = req.getCookies();
  21.     if (cookies != null) {
  22.       for (int i = 0; i < cookies.length; i++) {
  23.         if (cookies[i].getName().equals("sessionid")) {
  24.           sessionid = cookies[i].getValue();
  25.           break;
  26.         }
  27.       }
  28.     }
  29.  
  30.     // If the session ID wasn't sent, generate one.
  31.     // Then be sure to send it to the client with the response.
  32.     if (sessionid == null) {
  33.       sessionid = generateSessionId();
  34.       Cookie c = new Cookie("sessionid", sessionid);
  35.       res.addCookie(c);
  36.     }
  37.  
  38.     out.println("<HEAD><TITLE>Current Shopping Cart Items</TITLE></HEAD>");
  39.     out.println("<BODY>");
  40.  
  41.     // Cart items are associated with the session ID
  42.     String[] items = getItemsFromCart(sessionid);
  43.  
  44.     // Print the current cart items.
  45.     out.println("You currently have the following items in your cart:<BR>");
  46.     if (items == null) {
  47.       out.println("<B>None</B>");
  48.     } else {
  49.       out.println("<UL>");
  50.       for (int i = 0; i < items.length; i++) {
  51.         out.println("<LI>" + items[i]);
  52.       }
  53.       out.println("</UL>");
  54.     }
  55.  
  56.     // Ask if they want to add more items or check out.
  57.     out.println("<FORM ACTION="/servlet/ShoppingCart" METHOD=POST>");
  58.     out.println("Would you like to<BR>");
  59.     out.println("<INPUT TYPE=SUBMIT VALUE=" Add More Items ">");
  60.     out.println("<INPUT TYPE=SUBMIT VALUE=" Check Out ">");
  61.     out.println("</FORM>");
  62.  
  63.     // Offer a help page.
  64.     out.println("For help, click <A HREF="/servlet/Help"
  65.         + "?topic=ShoppingCartViewerCookie">here</A>");
  66.  
  67.     out.println("</BODY></HTML>");
  68.   }
  69.  
  70.   private static String generateSessionId() throws UnsupportedEncodingException {
  71.     String uid = new java.rmi.server.UID().toString(); // guaranteed unique
  72.     return URLEncoder.encode(uid,"UTF-8"); // encode any special chars
  73.   }
  74.  
  75.   private static String[] getItemsFromCart(String sessionid) {
  76.     return new String[]{"a","b"};  
  77.   }
  78. }

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