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.Method;
22 import java.lang.reflect.Proxy;
23 import java.util.Arrays;
24 import java.util.HashSet;
25 import java.util.Set;
26
27 import org.apache.commons.lang3.reflect.MethodUtils;
28
29 /**
30 * Provides some useful event-based utility methods.
31 *
32 * @since 3.0
33 */
34 public class EventUtils {
35
36 private static final class EventBindingInvocationHandler implements InvocationHandler {
37 private final Object target;
38 private final String methodName;
39 private final Set<String> eventTypes;
40
41 /**
42 * Creates a new instance of {@link EventBindingInvocationHandler}.
43 *
44 * @param target the target object for method invocations
45 * @param methodName the name of the method to be invoked
46 * @param eventTypes the names of the supported event types
47 */
48 EventBindingInvocationHandler(final Object target, final String methodName, final String[] eventTypes) {
49 this.target = target;
50 this.methodName = methodName;
51 this.eventTypes = new HashSet<>(Arrays.asList(eventTypes));
52 }
53
54 /**
55 * Checks whether a method for the passed in parameters can be found.
56 *
57 * @param method the listener method invoked
58 * @return a flag whether the parameters could be matched
59 */
60 private boolean hasMatchingParametersMethod(final Method method) {
61 return MethodUtils.getAccessibleMethod(target.getClass(), methodName, method.getParameterTypes()) != null;
62 }
63
64 /**
65 * Handles a method invocation on the proxy object.
66 *
67 * @param proxy the proxy instance
68 * @param method the method to be invoked
69 * @param parameters the parameters for the method invocation
70 * @return the result of the method call
71 * @throws Throwable if an error occurs
72 */
73 @Override
74 public Object invoke(final Object proxy, final Method method, final Object[] parameters) throws Throwable {
75 if (eventTypes.isEmpty() || eventTypes.contains(method.getName())) {
76 if (hasMatchingParametersMethod(method)) {
77 return MethodUtils.invokeMethod(target, methodName, parameters);
78 }
79 return MethodUtils.invokeMethod(target, methodName);
80 }
81 return null;
82 }
83 }
84
85 /**
86 * Adds an event listener to the specified source. This looks for an "add" method corresponding to the event
87 * type (addActionListener, for example).
88 * @param eventSource the event source
89 * @param listenerType the event listener type
90 * @param listener the listener
91 * @param <L> the event listener type
92 *
93 * @throws IllegalArgumentException if the object doesn't support the listener type
94 */
95 public static <L> void addEventListener(final Object eventSource, final Class<L> listenerType, final L listener) {
96 try {
97 MethodUtils.invokeMethod(eventSource, "add" + listenerType.getSimpleName(), listener);
98 } catch (final ReflectiveOperationException e) {
99 throw new IllegalArgumentException("Unable to add listener for class " + eventSource.getClass().getName()
100 + " and public add" + listenerType.getSimpleName()
101 + " method which takes a parameter of type " + listenerType.getName() + ".");
102 }
103 }
104
105 /**
106 * Binds an event listener to a specific method on a specific object.
107 *
108 * @param <L> the event listener type
109 * @param target the target object
110 * @param methodName the name of the method to be called
111 * @param eventSource the object which is generating events (JButton, JList, etc.)
112 * @param listenerType the listener interface (ActionListener.class, SelectionListener.class, etc.)
113 * @param eventTypes the event types (method names) from the listener interface (if none specified, all will be
114 * supported)
115 */
116 public static <L> void bindEventsToMethod(final Object target, final String methodName, final Object eventSource,
117 final Class<L> listenerType, final String... eventTypes) {
118 final L listener = listenerType.cast(Proxy.newProxyInstance(target.getClass().getClassLoader(),
119 new Class[] { listenerType }, new EventBindingInvocationHandler(target, methodName, eventTypes)));
120 addEventListener(eventSource, listenerType, listener);
121 }
122
123 /**
124 * Make private in 4.0.
125 *
126 * @deprecated TODO Make private in 4.0.
127 */
128 @Deprecated
129 public EventUtils() {
130 // empty
131 }
132 }