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Java > Open Source Codes > sample > duplicate > Main


1 package sample.duplicate;
2
3 /*
4   Runtime metaobject (JDK 1.2 or later only).
5
6   With the javassist.reflect package, the users can attach a metaobject
7   to an object. The metaobject can control the behavior of the object.
8   For example, you can implement fault tolerancy with this ability. One
9   of the implementation techniques of fault tolernacy is to make a copy
10   of every object containing important data and maintain it as a backup.
11   If the machine running the object becomes down, the backup object on a
12   different machine is used to continue the execution.
13
14   To make the copy of the object a real backup, all the method calls to
15   the object must be also sent to that copy. The metaobject is needed
16   for this duplication of the method calls. It traps every method call
17   and invoke the same method on the copy of the object so that the
18   internal state of the copy is kept equivalent to that of the original
19   object.
20
21   First, run sample.duplicate.Viewer without a metaobject.
22
23   % java sample.duplicate.Viewer
24
25   This program shows a ball in a window.
26
27   Then, run the same program with a metaobject, which is an instance
28   of sample.duplicate.DuplicatedObject.
29
30   % java sample.duplicate.Main
31
32   You would see two balls in a window. This is because
33   sample.duplicate.Viewer is loaded by javassist.reflect.Loader so that
34   a metaobject would be attached.
35 */
36 public class Main {
37     public static void main(String JavaDoc[] args) throws Throwable JavaDoc {
38     javassist.reflect.Loader cl = new javassist.reflect.Loader();
39     cl.makeReflective("sample.duplicate.Ball",
40               "sample.duplicate.DuplicatedObject",
41               "javassist.reflect.ClassMetaobject");
42     cl.run("sample.duplicate.Viewer", args);
43     }
44 }
45
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