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git-svn-id: http://anonsvn.jboss.org/repos/javassist/trunk@6 30ef5769-5b8d-40dd-aea6-55b5d6557bb3

4 files changed, 204 insertions, 0 deletions

diff --git a/sample/duplicate/Ball.java b/sample/duplicate/Ball.java
new file mode 100644
index 00000000..21d6e1cf
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+++ b/sample/duplicate/Ball.java
@@ -0,0 +1,44 @@
+package sample.duplicate;

+

+import java.awt.Graphics;

+import java.awt.Color;

+

+public class Ball {

+    private int x, y;

+    private Color color;

+    private int radius = 30;

+    private boolean isBackup = false;

+

+    public Ball(int x, int y) {

+	move(x, y);

+	changeColor(Color.orange);

+    }

+

+    // This constructor is for a backup object.

+    public Ball(Ball b) {

+	isBackup = true;

+    }

+

+    // Adjust the position so that the backup object is visible.

+    private void adjust() {

+	if (isBackup) {

+	    this.x += 50;

+	    this.y += 50;

+	}

+    }

+

+    public void paint(Graphics g) {

+	g.setColor(color);

+	g.fillOval(x, y, radius, radius);

+    }

+

+    public void move(int x, int y) {

+	this.x = x;

+	this.y = y;

+	adjust();

+    }

+

+    public void changeColor(Color color) {

+	this.color = color;

+    }

+}

diff --git a/sample/duplicate/DuplicatedObject.java b/sample/duplicate/DuplicatedObject.java
new file mode 100644
index 00000000..5995abcc
--- /dev/null
+++ b/sample/duplicate/DuplicatedObject.java
@@ -0,0 +1,38 @@
+package sample.duplicate;

+

+import javassist.reflect.*;

+

+public class DuplicatedObject extends Metaobject {

+    private DuplicatedObject backup;

+

+    // if a base-level object is created, this metaobject creates

+    // a copy of the base-level object.

+

+    public DuplicatedObject(Object self, Object[] args) {

+	super(self, args);

+	ClassMetaobject clazz = getClassMetaobject();

+	if (clazz.isInstance(args[0]))

+	    backup = null;	// self is a backup object.

+	else {

+	    Object[] args2 = new Object[1];

+	    args2[0] = self;

+	    try {

+		Metalevel m = (Metalevel)clazz.newInstance(args2);

+		backup = (DuplicatedObject)m._getMetaobject();

+	    }

+	    catch (CannotCreateException e) {

+		backup = null;

+	    }

+	}

+    }

+

+    public Object trapMethodcall(int identifier, Object[] args) 

+	throws Throwable

+    {

+	Object obj = super.trapMethodcall(identifier, args);

+	if (backup != null)

+	    backup.trapMethodcall(identifier, args);

+

+	return obj;

+    }

+}

diff --git a/sample/duplicate/Main.java b/sample/duplicate/Main.java
new file mode 100644
index 00000000..e152a23e
--- /dev/null
+++ b/sample/duplicate/Main.java
@@ -0,0 +1,44 @@
+package sample.duplicate;

+

+/*

+  Runtime metaobject (JDK 1.2 or later only).

+

+  With the javassist.reflect package, the users can attach a metaobject

+  to an object.  The metaobject can control the behavior of the object.

+  For example, you can implement fault tolerancy with this ability.  One

+  of the implementation techniques of fault tolernacy is to make a copy

+  of every object containing important data and maintain it as a backup.

+  If the machine running the object becomes down, the backup object on a

+  different machine is used to continue the execution.

+

+  To make the copy of the object a real backup, all the method calls to

+  the object must be also sent to that copy.  The metaobject is needed

+  for this duplication of the method calls.  It traps every method call

+  and invoke the same method on the copy of the object so that the

+  internal state of the copy is kept equivalent to that of the original

+  object.

+

+  First, run sample.duplicate.Viewer without a metaobject.

+

+  % java sample.duplicate.Viewer

+

+  This program shows a ball in a window.

+

+  Then, run the same program with a metaobject, which is an instance

+  of sample.duplicate.DuplicatedObject.

+

+  % java sample.duplicate.Main

+

+  You would see two balls in a window.  This is because

+  sample.duplicate.Viewer is loaded by javassist.reflect.Loader so that

+  a metaobject would be attached.

+*/

+public class Main {

+    public static void main(String[] args) throws Throwable {

+	javassist.reflect.Loader cl = new javassist.reflect.Loader();

+	cl.makeReflective("sample.duplicate.Ball",

+			  "sample.duplicate.DuplicatedObject",

+			  "javassist.reflect.ClassMetaobject");

+	cl.run("sample.duplicate.Viewer", args);

+    }

+}

diff --git a/sample/duplicate/Viewer.java b/sample/duplicate/Viewer.java
new file mode 100644
index 00000000..aec13f6b
--- /dev/null
+++ b/sample/duplicate/Viewer.java
@@ -0,0 +1,78 @@
+package sample.duplicate;

+

+import java.applet.*;

+import java.awt.*;

+import java.awt.event.*;

+

+public class Viewer extends Applet

+    implements MouseListener, ActionListener, WindowListener

+{

+    private static final Color[] colorList = {

+	Color.orange, Color.pink, Color.green, Color.blue };

+

+    private Ball ball;

+    private int colorNo;

+

+    public void init() {

+	colorNo = 0;

+	Button b = new Button("change");

+	b.addActionListener(this);

+	add(b);

+

+	addMouseListener(this);

+    }

+

+    public void start() {

+	ball = new Ball(50, 50);

+	ball.changeColor(colorList[0]);

+    }

+

+    public void paint(Graphics g) {

+	ball.paint(g);

+    }

+

+    public void mouseClicked(MouseEvent ev) {

+	ball.move(ev.getX(), ev.getY());

+	repaint();

+    }

+

+    public void mouseEntered(MouseEvent ev) {}

+

+    public void mouseExited(MouseEvent ev) {}

+

+    public void mousePressed(MouseEvent ev) {}

+

+    public void mouseReleased(MouseEvent ev) {}

+

+    public void actionPerformed(ActionEvent e) {

+	ball.changeColor(colorList[++colorNo % colorList.length]);

+	repaint();

+    }

+

+    public void windowOpened(WindowEvent e) {}

+

+    public void windowClosing(WindowEvent e) {

+	System.exit(0);

+    }

+

+    public void windowClosed(WindowEvent e) {}

+

+    public void windowIconified(WindowEvent e) {}

+

+    public void windowDeiconified(WindowEvent e) {}

+

+    public void windowActivated(WindowEvent e) {}

+

+    public void windowDeactivated(WindowEvent e) {}

+

+    public static void main(String[] args) {

+	Frame f = new Frame("Viewer");

+	Viewer view = new Viewer();

+	f.addWindowListener(view);

+	f.add(view);

+	f.setSize(300, 300);

+	view.init();

+	view.start();

+	f.setVisible(true);

+    }

+}