calculator3.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, Memento, Strategy and Factory Method.
 * 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 Calculator3 extends JtCommand {

    public static final String JtCLASS_NAME = Calculator3.class.getName(); 
    public static final String ADD = "ADD";
    public static final String MULTIPLY = "MULTIPLY";
    public static final String UNDO = "UNDO";

    private static final long serialVersionUID = 1L;
    transient Object state = null;        // Object state
    private int total = 0;                // Calculator Total
    private JtMemento memento = null;     // Contains the state of the object
    // needed to implement the undo operation



    public Calculator3 () {
    }

    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);   

    }

    // Save calculator state

    /*
  private void saveState () {

    JtMessage msg = new JtMessage ("JtENCODE_OBJECT");
    JtObject tmp = new JtObject();
    Object aux;

    msg.setMsgContent (this);
    aux = tmp.processMessage  (msg);

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

    // Use an instance of JtMemento to store the state

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

    memento.setState (aux);

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

  }


  private void restoreState () {

    JtMessage msg = new JtMessage ("JtDECODE_OBJECT");
    Calculator3 tmp;
    JtObject copier = new JtObject ();


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

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

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

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

    msg.setMsgContent (state);
    //tmp = (Calculator1) xmlHelper.processMessage (msg);
    tmp = (Calculator3) copier.processMessage (msg);

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

    //System.out.println ("...\n" + copier.processMessage (msg));
    //System.out.println ("src...\n" + tmp.getMessageLog ());


    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 (JtObject.JtXML_ENCODE);
    msg.setMsgContent (this);


  }
     */



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

    public Object processMessage (Object message) {

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

        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 (Calculator3.ADD)) {

            // Saves the state of the object
            saveState ();

            // Log the request (message). This method is inherited from JtCommand

            logMessage (msg);  

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

            return (new Integer (total));
        }


        if (msgid.equals (Calculator3.MULTIPLY)) {


            // Saves the state of the object
            saveState ();

            // Log the message   
            logMessage (msg);

            // Put together the MULTIPLY message

            tmp = new JtMessage (Calculator3.MULTIPLY);
            tmp.setMsgContent (new Integer (total));
            tmp.setMsgData (content);

            // the multiplication object (child of this object) is used
            // to process multiplications.

            mres = (Integer) sendMessage ("multiplication", tmp);      

            total = mres.intValue ();             

            return (new Integer (total));
        }


        if (msgid.equals (Calculator3.UNDO)) {


            restoreState ();

            return (new Integer (total));
        }

        // JtRemove message (Remove Object)

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

        handleError ("Calculator3.processMessage: invalid message id:" + msgid);
        return (null);
    }



    /**
     * Calculator implementation (main)
     */

    public static void main(String[] args) {

        JtObject main = new JtFactory ();
        JtMessage msg;
        Object total;
        JtKeyboard keyboard;
        String input;    
        int num = 0;
        Calculator3 calculator;
        Multiplication multiplication;


        // Create calculator, keyboard and multiplication

        calculator = (Calculator3) main.createObject (Calculator3.JtCLASS_NAME, "calculator");
        keyboard = (JtKeyboard) main.createObject (JtKeyboard.JtCLASS_NAME, "keyboard");
        multiplication = (Multiplication) calculator.createObject 
        ("Jt.examples.patterns.Multiplication", "multiplication");

        do {
            System.out.println  ("Please  select a multiplication strategy ...");
            System.out.println  ("1. Standard multiplication");
            System.out.println  ("2. Repetitive addition");

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

            if (input == null)
                continue;

            input = input.trim ();

            if (input.equals ("1")) {
                main.setValue (multiplication, "concreteStrategy", new MultiplicationA ());
                break;
            } else  if (input.equals ("2")) {
                main.setValue (multiplication, "concreteStrategy", new MultiplicationB ());
                break;
            }
        } while (true);

        for (;;) {

            System.out.println  ("Please  select an operation ...");
            System.out.println  ("1. Addition");
            System.out.println  ("2. Multiplication");
            System.out.println  ("3. Undo the last operation");
            System.out.println  ("4. Exit");


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

            input = input.trim ();

            if (input.equals ("4"))
                break;

            if ("3".equals (input)) {
                msg =  new JtMessage (Calculator3.UNDO);
                main.sendMessage ("calculator", msg);
                System.out.println 
                (">>> Total:" + main.getValue ("calculator", "total") + " <<<");
                continue;
            }

            if (input.equals ("1")) {
                msg =  new JtMessage (Calculator3.ADD);
            } else if (input.equals ("2")) {
                msg =  new JtMessage (Calculator3.MULTIPLY);
            } else
                continue;

            System.out.print ("Enter a number --> ");


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

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

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

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


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

                System.err.println (e);
                continue;
            }


            // Add the number to the Total (ADD Message)
            //msg =  new JtMessage ("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 main 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");        

    }

}