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Java > Open Source Codes > org > jboss > aspects > patterns > observable > SubjectInterceptor


1 /*
2   * JBoss, Home of Professional Open Source
3   * Copyright 2005, JBoss Inc., and individual contributors as indicated
4   * by the @authors tag. See the copyright.txt in the distribution for a
5   * full listing of individual contributors.
6   *
7   * This is free software; you can redistribute it and/or modify it
8   * under the terms of the GNU Lesser General Public License as
9   * published by the Free Software Foundation; either version 2.1 of
10   * the License, or (at your option) any later version.
11   *
12   * This software is distributed in the hope that it will be useful,
13   * but WITHOUT ANY WARRANTY; without even the implied warranty of
14   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15   * Lesser General Public License for more details.
16   *
17   * You should have received a copy of the GNU Lesser General Public
18   * License along with this software; if not, write to the Free
19   * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20   * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
21   */
22 package org.jboss.aspects.patterns.observable;
23
24 import org.jboss.aop.advice.Interceptor;
25 import org.jboss.aop.joinpoint.FieldInvocation;
26 import org.jboss.aop.joinpoint.Invocation;
27
28 /**
29  * A Subject Interceptor. Traps changes to the object
30  * and fires change notifications.
31  *
32  * @author <a HREF="adrian@jboss.com">Adrian Brock</a>
33  * @version $Revision: 37406 $
34  */
35 public class SubjectInterceptor implements Interceptor
36 {
37    public String JavaDoc getName()
38    {
39       return "Observerable";
40    }
41
42    public Object JavaDoc invoke(Invocation invocation) throws Throwable JavaDoc
43    {
44       FieldInvocation fi = (FieldInvocation) invocation;
45       Object JavaDoc before = fi.getField().get(fi.getTargetObject());
46       Object JavaDoc result = invocation.invokeNext();
47       Object JavaDoc after = fi.getField().get(fi.getTargetObject());
48       if ((before == null && after != null) || (before != null && before.equals(after) == false))
49       {
50          Subject observable = (Subject) fi.getTargetObject();
51          observable.notifyObservers();
52       }
53       return result;
54    }
55 }
56
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