calculator1.java

Java Pattern Oriented Framework (Jt) 是为了实现Java快速开发的面向模式的框架。

package Jt.examples.patterns;

import Jt.*;
import Jt.xml.JtXMLHelper;

/**
 * Calculator implementation based on Command and Memento.
 * Creating a subclass of JtCommand and implementing the processMessage
 * method is basically all that is needed. Command requests are logged via
 * the inherited LogMessage method. 
 */

public class Calculator1 extends JtCommand {

    public static final String JtCLASS_NAME = Calculator1.class.getName(); 
    private static final long serialVersionUID = 1L;
    transient Object state = null;        // Object state
    private int total = 0;                // Calculator Total
    transient private JtMemento memento;  // Contains the state of the object
                                          // needed to implement the undo operation
    public static final String ADD = "ADD";
    public static final String UNDO = "UNDO";
    


    public Calculator1 () {
    }

    public void setTotal (int total) {
        this.total = total;
    }

    public int getTotal () {
        return (total);
    }


    // save the state using JtMemento

    private void saveState () {

        JtMessage msg = new JtMessage (JtMemento.JtSAVE);

        if (memento == null)
            memento = new JtMemento ();

        msg.setMsgContent(this);   
        sendMessage (memento, msg);   

    }

    // restore the state using JtMemento

    private void restoreState () {

        JtMessage msg = new JtMessage (JtMemento.JtRESTORE);


        if (memento == null) {
            handleWarning ("restoreState: nothing to undo ....");
            return;
        }

        msg.setMsgContent(this);   
        sendMessage (memento, msg);   

    }


    /*
  private void saveState () {

    JtMessage msg = new JtMessage (JtObject.JtXML_ENCODE);

    JtObject tmp = new JtObject();

    msg.setMsgContent (this);


    state = tmp.processMessage  (msg);

    if (state == null) {
      handleWarning ("saveSate: Unable to save the current state"); //check
      return;
    }

    if (memento == null)
      memento = new JtMemento ();

    memento.setState (state);

    handleTrace ("saveState: saving state ...\n" + state);

  }
     */

    /*
  private void restoreState () {

    JtMessage msg = new JtMessage ("JtDECODE_OBJECT");
    Calculator1 tmp;
    JtObject copier = new JtObject ();


    if (memento == null) {
      handleWarning ("restoreState: nothing to undo ....");
      return;
    }

    state = memento.getState ();
    memento = null;

    if (state == null) {
      handleWarning ("restoreState: nothing to undo ....");
      return;
    }

    handleTrace ("restoreState (state) ...\n" + state);

    msg.setMsgContent (state);
    //tmp = (Calculator1) xmlHelper.processMessage (msg);
    tmp = (Calculator1) copier.processMessage (msg);

    msg = new JtMessage (JtObject.JtXML_ENCODE);
    msg.setMsgContent (tmp);

    msg = new JtMessage ("JtCOPY");

    if (tmp == null) {
      handleTrace ("restoreState failed: unable to convert object from XML"); 
      return;
    }

    msg.setMsgContent (tmp);
    msg.setMsgData (this);
    sendMessage (copier, msg);

    msg = new JtMessage ("JtENCODE_OBJECT");
    msg.setMsgContent (this);
  }
     */


    /**
     * Process object messages (Command requests).
     * <ul>
     * <li>JtADD - Add a number (msgContent) to the total
     * </ul>
     */

    public Object processMessage (Object message) {

        String msgid = null;
        JtMessage msg = (JtMessage) message;
        Object content;

        if (msg == null)
            return null;

        // Retrieve Message ID and content

        msgid = (String) msg.getMsgId ();

        if (msgid == null)
            return null;

        content = msg.getMsgContent();

        // Add a number to the total

        if (msgid.equals (Calculator1.ADD)) {


            saveState ();

            // Log the message   
            logMessage (msg);  

            total += ((Integer) content).intValue ();    



            return (new Integer (total));
        }


        if (msgid.equals (Calculator1.UNDO)) {



            restoreState ();

            // Log the message 
            // logMessage (msg);  
            return (new Integer (total));
        }

        // JtRemove message (Remove Object)

        if (msgid.equals (JtObject.JtREMOVE)) {
            return (null);
        }

        handleError ("Calculator1.processMessage: invalid message id:" + msgid);
        return (null);
    }



    /**
     * Calculator implementation (main)
     */

    public static void main(String[] args) {

        JtFactory main = new JtFactory ();
        JtMessage msg;
        Object total;
        JtKeyboard keyboard;
        String input;    
        int num = 0;
        Calculator1 calculator;

        // Create calculator and Keyboard

        calculator = (Calculator1) main.createObject (Calculator1.JtCLASS_NAME, "calculator");
        keyboard = (JtKeyboard) main.createObject (JtKeyboard.JtCLASS_NAME, "keyboard");

        System.out.println 
        ("Enter a number to be added to the total or 'U' to undo the last operation  (or <CR> to exit):");

        for (;;) {

            // Read input (number) from the keyboard (JtACTIVATE message)

            input = (String) main.sendMessage (keyboard, new JtMessage (JtObject.JtACTIVATE));

            if (input != null)
                input = input.trim ();


            if ("".equals (input)) 
                break;


            if ("U".equals (input) || "u".equals (input)) {
                msg =  new JtMessage (Calculator1.UNDO);
                main.sendMessage ("calculator", msg);
                System.out.println ("Total:" + main.getValue ("calculator", "total"));
                continue;
            }


            try {
                num = Integer.parseInt (input);
            } catch (Exception e) {

                System.err.println (e);
            }


            // Add the number to the Total (ADD Message)
            msg =  new JtMessage (Calculator1.ADD);
            msg.setMsgContent (new Integer (num));   
            total = main.sendMessage ("calculator", msg);

            System.out.println ("Total:" + total);

        }

        // Print the log (list of requests executed by the Calculator)
        // Use JtXMLHelper to convert the log information (messageLog)
        // into XML.

        msg = new JtMessage (JtObject.JtXML_ENCODE);
        msg.setMsgContent (main.getValue ("calculator", "messageLog"));

        System.out.println ("Log:\n" + 
                main.sendMessage (new JtXMLHelper (), msg));


        // Remove object

        main.removeObject (calculator);        

    }

}