ControlEventSetDescriptor


1   package org.apache.beehive.controls.runtime.packaging;
2   
3   import java.beans.EventSetDescriptor  ;
4   import java.beans.IntrospectionException  ;
5   import java.beans.MethodDescriptor  ;
6   import java.lang.ref.Reference  ;
7   import java.lang.ref.SoftReference  ;
8   import java.lang.reflect.Method  ;
9   
10  /**
11   * The ControlEventSetDescriptor is a result of an infortunate evoluntary flaw in the 
12   * java.beans.EventSetDescriptor class.  The getListeners functionality for event sets was
13   * added after the initial implementation, and unfortunately, there is no constructor that
14   * let you specify <b>both</b> the MethodDescriptors for events <b>and</b> the getListener
15   * method.  To compensate for this, we must subclass and provide our own getGetListenerMethod
16   * implementation.
17   */
18  public class ControlEventSetDescriptor extends EventSetDescriptor  
19  {
20      /**
21       * This constructor adds the getListenerMethod argument that is missing from the JDK!
22       */
23      public ControlEventSetDescriptor(String   eventSetName, Class  <?> listenerType,
24                                       MethodDescriptor  [] listenerMethodDescriptors,
25                                       Method   addListenerMethod, Method   removeListenerMethod,
26                                       Method   getListenerMethod)
27             throws IntrospectionException  
28      {
29          super(eventSetName, listenerType, listenerMethodDescriptors, 
30                addListenerMethod, removeListenerMethod);
31  
32          // Follow the same pattern as the JDK and store the method as a soft reference, so
33          // the introspector (alone) won't prevent Class garbage collection.
34          _getMethodRef = new SoftReference  <Method  >(getListenerMethod);
35      }
36  
37      /**
38       * Override the default implementation of getGetListenerMethod to return the method
39       * provided in the constructor.
40       */
41      public Method   getGetListenerMethod()
42      {
43          if (_getMethodRef == null)
44              return null;
45  
46          return _getMethodRef.get();
47      }
48  
49      Reference  <Method  > _getMethodRef;
50  }
51
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