1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.commons.lang3.event;
19
20 import java.lang.reflect.InvocationHandler;
21 import java.lang.reflect.InvocationTargetException;
22 import java.lang.reflect.Method;
23 import java.lang.reflect.Proxy;
24 import java.util.Arrays;
25 import java.util.HashSet;
26 import java.util.Set;
27
28 import org.apache.commons.lang3.reflect.MethodUtils;
29
30 /**
31 * Provides some useful event-based utility methods.
32 *
33 * @since 3.0
34 * @version $Id: EventUtils.java 1436770 2013-01-22 07:09:45Z ggregory $
35 */
36 public class EventUtils {
37
38 /**
39 * Adds an event listener to the specified source. This looks for an "add" method corresponding to the event
40 * type (addActionListener, for example).
41 * @param eventSource the event source
42 * @param listenerType the event listener type
43 * @param listener the listener
44 * @param <L> the event listener type
45 *
46 * @throws IllegalArgumentException if the object doesn't support the listener type
47 */
48 public static <L> void addEventListener(final Object eventSource, final Class<L> listenerType, final L listener) {
49 try {
50 MethodUtils.invokeMethod(eventSource, "add" + listenerType.getSimpleName(), listener);
51 } catch (final NoSuchMethodException e) {
52 throw new IllegalArgumentException("Class " + eventSource.getClass().getName()
53 + " does not have a public add" + listenerType.getSimpleName()
54 + " method which takes a parameter of type " + listenerType.getName() + ".");
55 } catch (final IllegalAccessException e) {
56 throw new IllegalArgumentException("Class " + eventSource.getClass().getName()
57 + " does not have an accessible add" + listenerType.getSimpleName ()
58 + " method which takes a parameter of type " + listenerType.getName() + ".");
59 } catch (final InvocationTargetException e) {
60 throw new RuntimeException("Unable to add listener.", e.getCause());
61 }
62 }
63
64 /**
65 * Binds an event listener to a specific method on a specific object.
66 *
67 * @param <L> the event listener type
68 * @param target the target object
69 * @param methodName the name of the method to be called
70 * @param eventSource the object which is generating events (JButton, JList, etc.)
71 * @param listenerType the listener interface (ActionListener.class, SelectionListener.class, etc.)
72 * @param eventTypes the event types (method names) from the listener interface (if none specified, all will be
73 * supported)
74 */
75 public static <L> void bindEventsToMethod(final Object target, final String methodName, final Object eventSource,
76 final Class<L> listenerType, final String... eventTypes) {
77 final L listener = listenerType.cast(Proxy.newProxyInstance(target.getClass().getClassLoader(),
78 new Class[] { listenerType }, new EventBindingInvocationHandler(target, methodName, eventTypes)));
79 addEventListener(eventSource, listenerType, listener);
80 }
81
82 private static class EventBindingInvocationHandler implements InvocationHandler {
83 private final Object target;
84 private final String methodName;
85 private final Set<String> eventTypes;
86
87 /**
88 * Creates a new instance of {@code EventBindingInvocationHandler}.
89 *
90 * @param target the target object for method invocations
91 * @param methodName the name of the method to be invoked
92 * @param eventTypes the names of the supported event types
93 */
94 EventBindingInvocationHandler(final Object target, final String methodName, final String[] eventTypes) {
95 this.target = target;
96 this.methodName = methodName;
97 this.eventTypes = new HashSet<String>(Arrays.asList(eventTypes));
98 }
99
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 @Override
110 public Object invoke(final Object proxy, final Method method, final Object[] parameters) throws Throwable {
111 if (eventTypes.isEmpty() || eventTypes.contains(method.getName())) {
112 if (hasMatchingParametersMethod(method)) {
113 return MethodUtils.invokeMethod(target, methodName, parameters);
114 } else {
115 return MethodUtils.invokeMethod(target, methodName);
116 }
117 }
118 return null;
119 }
120
121 /**
122 * Checks whether a method for the passed in parameters can be found.
123 *
124 * @param method the listener method invoked
125 * @return a flag whether the parameters could be matched
126 */
127 private boolean hasMatchingParametersMethod(final Method method) {
128 return MethodUtils.getAccessibleMethod(target.getClass(), methodName, method.getParameterTypes()) != null;
129 }
130 }
131 }