001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018 package org.apache.commons.lang3.event;
019
020 import java.lang.reflect.InvocationHandler;
021 import java.lang.reflect.InvocationTargetException;
022 import java.lang.reflect.Method;
023 import java.lang.reflect.Proxy;
024 import java.util.Arrays;
025 import java.util.HashSet;
026 import java.util.Set;
027
028 import org.apache.commons.lang3.reflect.MethodUtils;
029
030 /**
031 * Provides some useful event-based utility methods.
032 *
033 * @since 3.0
034 * @version $Id: EventUtils.java 1091072 2011-04-11 13:42:03Z mbenson $
035 */
036 public class EventUtils {
037
038 /**
039 * Adds an event listener to the specified source. This looks for an "add" method corresponding to the event
040 * type (addActionListener, for example).
041 * @param eventSource the event source
042 * @param listenerType the event listener type
043 * @param listener the listener
044 * @param <L> the event listener type
045 *
046 * @throws IllegalArgumentException if the object doesn't support the listener type
047 */
048 public static <L> void addEventListener(Object eventSource, Class<L> listenerType, L listener) {
049 try {
050 MethodUtils.invokeMethod(eventSource, "add" + listenerType.getSimpleName(), listener);
051 } catch (NoSuchMethodException e) {
052 throw new IllegalArgumentException("Class " + eventSource.getClass().getName()
053 + " does not have a public add" + listenerType.getSimpleName()
054 + " method which takes a parameter of type " + listenerType.getName() + ".");
055 } catch (IllegalAccessException e) {
056 throw new IllegalArgumentException("Class " + eventSource.getClass().getName()
057 + " does not have an accessible add" + listenerType.getSimpleName ()
058 + " method which takes a parameter of type " + listenerType.getName() + ".");
059 } catch (InvocationTargetException e) {
060 throw new RuntimeException("Unable to add listener.", e.getCause());
061 }
062 }
063
064 /**
065 * Binds an event listener to a specific method on a specific object.
066 *
067 * @param <L> the event listener type
068 * @param target the target object
069 * @param methodName the name of the method to be called
070 * @param eventSource the object which is generating events (JButton, JList, etc.)
071 * @param listenerType the listener interface (ActionListener.class, SelectionListener.class, etc.)
072 * @param eventTypes the event types (method names) from the listener interface (if none specified, all will be
073 * supported)
074 */
075 public static <L> void bindEventsToMethod(Object target, String methodName, Object eventSource,
076 Class<L> listenerType, String... eventTypes) {
077 final L listener = listenerType.cast(Proxy.newProxyInstance(target.getClass().getClassLoader(),
078 new Class[] { listenerType }, new EventBindingInvocationHandler(target, methodName, eventTypes)));
079 addEventListener(eventSource, listenerType, listener);
080 }
081
082 private static class EventBindingInvocationHandler implements InvocationHandler {
083 private final Object target;
084 private final String methodName;
085 private final Set<String> eventTypes;
086
087 /**
088 * Creates a new instance of {@code EventBindingInvocationHandler}.
089 *
090 * @param target the target object for method invocations
091 * @param methodName the name of the method to be invoked
092 * @param eventTypes the names of the supported event types
093 */
094 EventBindingInvocationHandler(final Object target, final String methodName, String[] eventTypes) {
095 this.target = target;
096 this.methodName = methodName;
097 this.eventTypes = new HashSet<String>(Arrays.asList(eventTypes));
098 }
099
100 /**
101 * Handles a method invocation on the proxy object.
102 *
103 * @param proxy the proxy instance
104 * @param method the method to be invoked
105 * @param parameters the parameters for the method invocation
106 * @return the result of the method call
107 * @throws Throwable if an error occurs
108 */
109 public Object invoke(final Object proxy, final Method method, final Object[] parameters) throws Throwable {
110 if (eventTypes.isEmpty() || eventTypes.contains(method.getName())) {
111 if (hasMatchingParametersMethod(method)) {
112 return MethodUtils.invokeMethod(target, methodName, parameters);
113 } else {
114 return MethodUtils.invokeMethod(target, methodName);
115 }
116 }
117 return null;
118 }
119
120 /**
121 * Checks whether a method for the passed in parameters can be found.
122 *
123 * @param method the listener method invoked
124 * @return a flag whether the parameters could be matched
125 */
126 private boolean hasMatchingParametersMethod(final Method method) {
127 return MethodUtils.getAccessibleMethod(target.getClass(), methodName, method.getParameterTypes()) != null;
128 }
129 }
130 }