Use Java servlets sessions to tally golf scores. : Networks « J2ME « Java






Use Java servlets sessions to tally golf scores.

/*--------------------------------------------------
* Url_rewrite.java 
*
* Use Java servlets sessions to tally golf scores.
* Session management is done using url-rewriting.
*
* Example from the book:     Core J2ME Technology
* Copyright John W. Muchow   http://www.CoreJ2ME.com
* You may use/modify for any non-commercial purpose
*-------------------------------------------------*/
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.io.*;
import java.io.*;

public class Url_rewrite extends MIDlet implements CommandListener
{
  private Display display;      // Reference to display object 
  private Form fmMain;          // The main form
  private TextField tfScore;    // Enter new score
  private int indxTextField;    // Index on of the textfield
  private StringItem siTotal;   // Running total
  private Command cmExit;       // A Command to exit the MIDlet  
  private Command cmUpdate;     // Update score on servlet
  private int holeNumber = 1;   // Current hole
  private static final int MAX_HOLES = 18;
  private String url = "http://www.mycgiserver.com/servlet/corej2me.Url_rewriteServlet";

  public Url_rewrite()
  {
    display = Display.getDisplay(this);

    // Enter scores    
    tfScore = new TextField("Enter score for Hole #1", "", 2, TextField.NUMERIC);
    
    // Current running total
    siTotal = new StringItem("Total: ", "");

    // Commands
    cmExit = new Command("Exit", Command.EXIT, 1);
    cmUpdate = new Command("Send", Command.SCREEN,2);

    // Create Form, add components, listen for events
    fmMain = new Form("");
    
    // Save index of textfield, it is removed 
    // after entering 18 values
    indxTextField = fmMain.append(tfScore);
    fmMain.append(siTotal);
    fmMain.addCommand(cmExit);
    fmMain.addCommand(cmUpdate);
    fmMain.setCommandListener(this);   
  }

  public void startApp()
  {
    display.setCurrent(fmMain);
  }    
    
  public void pauseApp()
  { }

  public void destroyApp(boolean unconditional)
  { }

  /*--------------------------------------------------
  * Process events
  *-------------------------------------------------*/  
  public void commandAction(Command c, Displayable s)
  {
    if (c == cmExit)
    {
      destroyApp(false);
      notifyDestroyed();
    } 
    else if (c == cmUpdate)  // Send score for next hole
    {
      // If nothing in the text field or max scores entered
      if (tfScore.getString().equals("") || holeNumber > MAX_HOLES)
        return;
      else
      {
        try
        {
          // Update the score on remote server
          updateTotal(tfScore.getString());
        
          // If entered the maximum, remove the 
          // textfield from the form
          if (++holeNumber > MAX_HOLES)
          {
            fmMain.delete(indxTextField);
            return;
          }
  
          // Change the label & reset contents
          tfScore.setLabel("Enter score for Hole #" + holeNumber);
          tfScore.setString("");
        }
        catch (Exception e)
        {
          System.err.println("Msg: " + e.toString());
        }
      }
    }     
  }

  /*--------------------------------------------------
  * Send client request. Receive server response
  *
  * Client: Send score for next hole.
  *
  * Server: Check for custom header 'Custom-newURL'
  *         If found, update the MIDlet URL for all
  *         future requests. Any data returned is 
  *         current total for all scores entered.
  *-------------------------------------------------*/
  private void updateTotal(String score) throws IOException
  {
    HttpConnection http = null;
    InputStream iStrm = null;    
    boolean ret = false;
     
    try
    {
      // When using GET, append data onto the url
      String completeURL = url + "?" + "score=" + score;
      
      http = (HttpConnection) Connector.open(completeURL);
      
      //----------------
      // Client Request
      //----------------
      // 1) Send request method
      http.setRequestMethod(HttpConnection.GET);

      // 2) Send header information - none
      
      // If you experience connection/IO problems, try 
      // removing the comment from the following line
      //http.setRequestProperty("Connection", "close");      
      
      // 3) Send body/data -  data is at the end of URL

      //----------------
      // Server Response
      //----------------
      iStrm = http.openInputStream();      

      // 1) Get status Line - ignore for now
        // System.out.println("Msg: " + http.getResponseMessage());                  
        // System.out.println("Code: " + http.getResponseCode());                
      
      // 2) Get header information 
      // See if header includes a rewritten url
      // if yes, update url for all future servlet requests
      String URLwithID = http.getHeaderField("Custom-newURL");
      
      if (URLwithID != null)
        url = URLwithID;
     
      // 3) Get body/data - the new running total is returned
      String str;
      int length = (int) http.getLength();
      if (length != -1)
      {
        byte servletData[] = new byte[length];
        iStrm.read(servletData);
        str = new String(servletData);
      }
      else  // Length not available...
      {
        ByteArrayOutputStream bStrm = new ByteArrayOutputStream();       
      
        int ch;
        while ((ch = iStrm.read()) != -1)
          bStrm.write(ch);

        str = new String(bStrm.toByteArray());
        bStrm.close();                        
       }

      // Update the stringitem that shows total
      siTotal.setText(str);
    }
    finally
    {
      // Clean up
      if (iStrm != null)
        iStrm.close();
      if (http != null)
        http.close();
    }
  }
}

/*--------------------------------------------------
* Url_rewriteServlet.java
*
* Use url-rewriting to manage sessions.
* Keeps a running total of golf scores for a 
* round of 18 holes (client sends score for each
* hole, one at a time).
*
* Example from the book:     Core J2ME Technology
* Copyright John W. Muchow   http://www.CoreJ2ME.com
* You may use/modify for any non-commercial purpose
*-------------------------------------------------*/
//package corej2me; // Required for mycgiserver.com

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

public class Url_rewriteServlet extends HttpServlet
{
  /*--------------------------------------------------
  * Initialize the servlet
  *-------------------------------------------------*/  
  public void init(ServletConfig config) throws ServletException
  {
    super.init(config);
  }

  /*--------------------------------------------------
  * Handle a GET request from client
  *-------------------------------------------------*/  
  protected void doGet(HttpServletRequest req, HttpServletResponse res) 
                       throws ServletException, IOException
  {
    try
    {
      // Get session information
      HttpSession session = req.getSession(true);
      
      // If a new session, we need to rewrite the URL for client
      if (session.isNew())
      {
        // Get the URL that got us here
        String incomingURL = HttpUtils.getRequestURL(req).toString();
        
        // Encode by adding session ID onto URL
        String URLwithID = res.encodeURL(incomingURL);
        
        // Send back a header to client with new re-written URL
        res.setHeader("Custom-newURL", URLwithID);
      }

      // Get the next score (parameter) passed in
      int nextScore = Integer.parseInt(req.getParameter("score"));
  
      // Get the ongoing total saved as part of the session
      // Convert to an integer "object"
      Integer sessionTotal = (Integer) session.getValue("sessionTotal");      

      // Running total from session and score passed in            
      int runningTotal = nextScore;
      if (sessionTotal != null)
        runningTotal += sessionTotal.intValue();

      // Update the session total, must save as an "object"      
      session.putValue("sessionTotal", new Integer(runningTotal));

      // Send back to client the new running total
      res.setContentType("text/plain");
      PrintWriter out = res.getWriter();
      out.write(Integer.toString(runningTotal));
      out.close();
    }
    catch (Exception e)
    {
      System.err.println("Msg: " + e.toString());
    }
  }

  /*--------------------------------------------------
  * Information about servlet
  *-------------------------------------------------*/
  public String getServletInfo()
  {
    return "Url_rewriteServlet 1.0 - John W. Muchow - www.corej2me.com";
  }
}
           
       








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