SubjectInterceptor


1   package dynaop.observer;
2   
3   import java.io.Serializable  ;
4   
5   import dynaop.Interceptor;
6   import dynaop.Invocation;
7   
8   /**
9    * Notifies observers after the method invocation completes. 
10   * Does not notify in the event of an exception. 
11   * Use in conjunction with <code>SubjectMixin</code>.
12   * 
13   * @author Bob Lee (crazybob@crazybob.org)
14   */
15  public class SubjectInterceptor implements Interceptor, Serializable   {
16  
17      private Object   argument;
18      
19      public SubjectInterceptor() {
20      }
21      
22      public SubjectInterceptor(Object   argument) {
23          this.argument = argument;
24      }
25      
26      /**
27       * Creates argument that should be passed to observers. Default 
28       * implementation returns <code>null</code>.
29       */
30      protected Object   createArgument(Subject subject,
31              Invocation invocation, Object   result) {
32          return this.argument;
33      }
34  
35      public Object   intercept(Invocation invocation) throws Throwable   {
36          Object   result = invocation.proceed();
37          
38          Subject subject = (Subject) invocation.getProxy();
39          subject.notifyObservers(createArgument(subject, invocation, result));
40          
41          return result;
42      }
43  }
44

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