eventhandler.java

gcc的组建

    try
      {
      actionMethod = targetClass.getMethod(action, null);
      }
    catch(NoSuchMethodException nsme)
      {
        // Note: If we want to be really strict the specification says that a no-argument method should
        // accept an EventObject (or subclass I guess). However since the official implementation is broken
        // anyways, it's more flexible without the EventObject restriction and we are compatible on everything
        // else this can stay this way.
        if(arguments != null && arguments.length >= 1/* && arguments[0] instanceof EventObject*/) {
            Class[] targetArgTypes = new Class[] { initClass(arguments[0].getClass()) };
            
            while(targetArgTypes[0] != null) {
                try
                {
                  // If no property exists we expect the first element of the arguments to be
                  // an EventObject which is then applied to the target method.
      
                  actionMethod = targetClass.getMethod(action, targetArgTypes);
              
                  return actionMethod.invoke(target, new Object[] { arguments[0] });
                }
                catch(NoSuchMethodException nsme2)
                {
                    
                }
                
                targetArgTypes[0] = nextClass(targetArgTypes[0]);
            }
          
        }
      }

    // If we do not have a Method instance at this point this means that all our tries
    // failed. The JDK throws an ArrayIndexOutOfBoundsException in this case.
    if(actionMethod == null)
      throw new ArrayIndexOutOfBoundsException(0);
    
    // Invoke target.action(property)
    return actionMethod.invoke(target, null);
      } catch(InvocationTargetException ite) {
         throw new RuntimeException(ite.getCause());
      } catch(IllegalAccessException iae) {
          // Cannot happen because we always use getMethod() which returns public
          // methods only. Otherwise there is something seriously broken in
          // GNU Classpath.
          throw (InternalError) new InternalError("Non-public method was invoked.").initCause(iae);
      }
  }
  
  /**
   * <p>Returns the primitive type for every wrapper class or the
   * class itself if it is no wrapper class.</p>
   * 
   * <p>This is needed because to be able to find both kinds of methods:
   * One that takes a wrapper class as the first argument and one that
   * accepts a primitive instead.</p>
   */
  private Class initClass(Class klass) {
   if(klass == Boolean.class) {
    return Boolean.TYPE;    
   } else if(klass == Byte.class) {
    return Byte.TYPE;   
   } else if(klass == Short.class) {
    return Short.TYPE;   
   } else if(klass == Integer.class) {
    return Integer.TYPE;   
   } else if(klass == Long.class) {
    return Long.TYPE;   
   } else if(klass == Float.class) {
    return Float.TYPE;   
   } else if(klass == Double.class) {
    return Double.TYPE;   
   } else {
    return klass;   
   }
  }

  /**
   * 
   * 
   * @param klass
   * @return
   */
  private Class nextClass(Class klass) {
    if(klass == Boolean.TYPE) {
    return Boolean.class;    
   } else if(klass == Byte.TYPE) {
    return Byte.class;   
   } else if(klass == Short.TYPE) {
    return Short.class;   
   } else if(klass == Integer.TYPE) {
    return Integer.class;   
   } else if(klass == Long.TYPE) {
    return Long.class;   
   } else if(klass == Float.TYPE) {
    return Float.class;   
   } else if(klass == Double.TYPE) {
    return Double.class;   
   } else {
    return klass.getSuperclass();
   }
   }
  
  /**
   * <p>Constructs an implementation of <code>listenerInterface</code>
   * to dispatch events.</p>
   * 
   * <p>You can use such an implementation to simply call a public
   * no-argument method of an arbitrary target object or to forward
   * the first argument of the listener method to the target method.</p>
   * 
   * <p>Call this method like:</p>
   * <code>
   * button.addActionListener((ActionListener)
   *    EventHandler.create(ActionListener.class, target, "dispose"));
   * </code>
   * 
   * <p>to achieve the following behavior:</p>
   * <code>
   * button.addActionListener(new ActionListener() {
   *    public void actionPerformed(ActionEvent ae) {
   *        target.dispose();
   *    }
   * });
   * </code>
   * 
   * <p>That means if you need a listener implementation that simply calls a
   * a no-argument method on a given instance for <strong>each</strong>
   * method of the listener interface.</p>
   * 
   * <p>Note: The <code>action</code> is interpreted as a method name. If your target object
   * has no no-argument method of the given name the EventHandler tries to find
   * a method with the same name but which can accept the first argument of the
   * listener method. Usually this will be an event object but any other object
   * will be forwarded, too. Keep in mind that using a property name instead of a
   * real method here is wrong and will throw an <code>ArrayIndexOutOfBoundsException</code>
   * whenever one of the listener methods is called.<p/>
   *
   * <p>The <code>EventHandler</code> will automatically convert primitives
   * to their wrapper class and vice versa. Furthermore it will call
   * a target method if it accepts a superclass of the type of the
   * first argument of the listener method.</p>
   * 
   * <p>In case that the method of the target object throws an exception
   * it will be wrapped in a <code>RuntimeException</code> and thrown out
   * of the listener method.</p>
   * 
   * <p>In case that the method of the target object cannot be found an
   * <code>ArrayIndexOutOfBoundsException</code> will be thrown when the
   * listener method is invoked.</p>
   * 
   * <p>A call to this method is equivalent to:
   * <code>create(listenerInterface, target, action, null, null)</code></p>
   *
   * @param listenerInterface Listener interface to implement.
   * @param target Object to invoke action on.
   * @param action Target property or method to invoke.
   * @return A constructed proxy object.
   */
  public static Object create(Class listenerInterface, Object target, String action)
  {
    return create(listenerInterface, target, action, null, null);
  }

  /**
   * <p>Constructs an implementation of <code>listenerInterface</code>
   * to dispatch events.</p>
   *
   * <p>Use this method if you want to create an implementation that retrieves
   * a property value from the <b>first</b> argument of the listener method
   * and applies it to the target's property or method. This first argument
   * of the listener is usually an event object but any other object is
   * valid, too.</p>
   * 
   * <p>You can set the value of <code>eventPropertyName</code> to "prop"
   * to denote the retrieval of a property named "prop" from the event
   * object. In case that no such property exists the <code>EventHandler</code>
   * will try to find a method with that name.</p>
   * 
   * <p>If you set <code>eventPropertyName</code> to a value like this "a.b.c"
   * <code>EventHandler</code> will recursively evaluate the properties "a", "b"
   * and "c". Again if no property can be found the <code>EventHandler</code>
   * tries a method name instead. This allows mixing the names, too: "a.toString"
   * will retrieve the property "a" from the event object and will then call
   * the method "toString" on it.</p>
   * 
   * <p>An exception thrown in any of these methods will provoke a
   * <code>RuntimeException</code> to be thrown which contains an
   * <code>InvocationTargetException</code> containing the triggering exception.</p>
   * 
   * <p>If you set <code>eventPropertyName</code> to a non-null value the
   * <code>action</code> parameter will be interpreted as a property name
   * or a method name of the target object.</p>
   *   
   * <p>Any object retrieved from the event object and applied to the
   * target will converted from primitives to their wrapper class or
   * vice versa or applied to a method that accepts a superclass
   * of the object.</p>
   *
   * <p>Examples:</p>
   * <p>The following code:</p><code>
   * button.addActionListener(
   *    new ActionListener() {
   *        public void actionPerformed(ActionEvent ae) {
   *            Object o = ae.getSource().getClass().getName();
   *            textField.setText((String) o);
   *        }
   *    });
   * </code>
   * 
   * <p>Can be expressed using the <code>EventHandler</code> like this:</p>
   * <p>
   * <code>button.addActionListener((ActionListener)
   *    EventHandler.create(ActionListener.class, textField, "text", "source.class.name");
   * <code>
   * </p>
   * 
   * <p>As said above you can specify the target as a method, too:</p>
   * <p>
   * <code>button.addActionListener((ActionListener)
   *    EventHandler.create(ActionListener.class, textField, "setText", "source.class.name");
   * <code>
   * </p>
   * 
   * <p>Furthermore you can use method names in the property:</p>
   * <p>
   * <code>button.addActionListener((ActionListener)
   *    EventHandler.create(ActionListener.class, textField, "setText", "getSource.getClass.getName");
   * <code>
   * </p>
   * 
   * <p>Finally you can mix names:</p>
   * <p>
   * <code>button.addActionListener((ActionListener)
   *    EventHandler.create(ActionListener.class, textField, "setText", "source.getClass.name");
   * <code>
   * </p>
   * 
   * <p>A call to this method is equivalent to:
   * <code>create(listenerInterface, target, action, null, null)</code>
   * </p>
   *
   * @param listenerInterface Listener interface to implement.
   * @param target Object to invoke action on.
   * @param action Target property or method to invoke.
   * @param eventPropertyName Name of property to extract from event.
   * @return A constructed proxy object.
   */
  public static Object create(Class listenerInterface, Object target,
			      String action, String eventPropertyName)
  {
    return create(listenerInterface, target, action, eventPropertyName, null);
  }

  /**
   * <p>Constructs an implementation of <code>listenerInterface</code>
   * to dispatch events.</p>
   *
   * <p>Besides the functionality described for {@link create(Class, Object, String)}
   * and {@link create(Class, Object, String, String)} this method allows you
   * to filter the listener method that should have an effect. Look at these
   * method's documentation for more information about the <code>EventHandler</code>'s
   * usage.</p>
   * 
   * <p>If you want to call <code>dispose</code> on a <code>JFrame</code> instance
   * when the <code>WindowListener.windowClosing()</code> method was invoked use
   * the following code:</p>
   * <p>
   * <code>
   * EventHandler.create(WindowListener.class, jframeInstance, "dispose", null, "windowClosing");
   * </code>
   * </p>
   * 
   * <p>A <code>NullPointerException</code> is thrown if the <code>listenerInterface</code>
   * or <code>target</code> argument are <code>null</code>.
   * 
   * @param listenerInterface Listener interface to implement.
   * @param target Object to invoke action on.
   * @param action Target method name to invoke.
   * @param eventPropertyName Name of property to extract from event.
   * @param listenerMethodName Listener method to implement.
   * @return A constructed proxy object.
   */
  public static Object create(Class listenerInterface, Object target,
			      String action, String eventPropertyName,
			      String listenerMethodName)
  {
    // Create EventHandler instance
    EventHandler eh = new EventHandler(target, action, eventPropertyName,
				       listenerMethodName);

    // Create proxy object passing in the event handler
    Object proxy = Proxy.newProxyInstance(listenerInterface.getClassLoader(),
					  new Class[] {listenerInterface},
					  eh);

    return proxy;
  }

}