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 * https://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.ObjectUtils;
28 import org.apache.commons.lang3.reflect.MethodUtils;
29
30 /**
31 * Provides some useful event-based utility methods.
32 *
33 * @since 3.0
34 */
35 public class EventUtils {
36
37 private static final class EventBindingInvocationHandler implements InvocationHandler {
38 private final Object target;
39 private final String methodName;
40 private final Set<String> eventTypes;
41
42 /**
43 * Creates a new instance of {@link EventBindingInvocationHandler}.
44 *
45 * @param target The target object for method invocations.
46 * @param methodName The name of the method to be invoked.
47 * @param eventTypes The names of the supported event types.
48 */
49 EventBindingInvocationHandler(final Object target, final String methodName, final String[] eventTypes) {
50 this.target = target;
51 this.methodName = methodName;
52 this.eventTypes = new HashSet<>(Arrays.asList(eventTypes));
53 }
54
55 /**
56 * Tests whether a method for the passed in parameters can be found.
57 *
58 * @param method The listener method invoked.
59 * @return A flag whether the parameters could be matched.
60 */
61 private boolean hasMatchingParametersMethod(final Method method) {
62 return MethodUtils.getAccessibleMethod(target.getClass(), methodName, method.getParameterTypes()) != null;
63 }
64
65 /**
66 * Handles a method invocation on the proxy object.
67 *
68 * @param proxy The proxy instance.
69 * @param method The method to be invoked.
70 * @param parameters The parameters for the method invocation.
71 * @return The result of the method call.
72 * @throws SecurityException Thrown if an underlying accessible object's method denies the request.
73 * @see SecurityManager#checkPermission
74 * @throws Throwable Thrown if an error occurs.
75 */
76 @Override
77 public Object invoke(final Object proxy, final Method method, final Object[] parameters) throws Throwable {
78 if (method.getDeclaringClass() == Object.class) {
79 // Handle Object methods locally instead of dispatching them to the bound target,
80 // mirroring java.beans.EventHandler: routine host actions (hash-based collections,
81 // logging, equality checks during listener de-registration) must not invoke the
82 // target method and must not return null into an unboxing context.
83 switch (method.getName()) {
84 case "hashCode":
85 return Integer.valueOf(System.identityHashCode(proxy));
86 case "equals":
87 return Boolean.valueOf(proxy == parameters[0]);
88 default: // toString
89 return ObjectUtils.identityToString(proxy);
90 }
91 }
92 if (eventTypes.isEmpty() || eventTypes.contains(method.getName())) {
93 if (hasMatchingParametersMethod(method)) {
94 return MethodUtils.invokeMethod(target, methodName, parameters);
95 }
96 return MethodUtils.invokeMethod(target, methodName);
97 }
98 return null;
99 }
100 }
101
102 /**
103 * Adds an event listener to the specified source. This looks for an "add" method corresponding to the event
104 * type (addActionListener, for example).
105 *
106 * @param eventSource The event source.
107 * @param listenerType The event listener type.
108 * @param listener The listener.
109 * @param <L> the event listener type.
110 * @throws IllegalArgumentException Thrown if the object doesn't support the listener type.
111 */
112 public static <L> void addEventListener(final Object eventSource, final Class<L> listenerType, final L listener) {
113 try {
114 MethodUtils.invokeMethod(eventSource, "add" + listenerType.getSimpleName(), listener);
115 } catch (final ReflectiveOperationException e) {
116 throw new IllegalArgumentException("Unable to add listener for class " + eventSource.getClass().getName()
117 + " and public add" + listenerType.getSimpleName()
118 + " method which takes a parameter of type " + listenerType.getName() + ".");
119 }
120 }
121
122 /**
123 * Binds an event listener to a specific method on a specific object.
124 *
125 * @param <L> the event listener type.
126 * @param target The target object.
127 * @param methodName The name of the method to be called.
128 * @param eventSource The object which is generating events (JButton, JList, etc.).
129 * @param listenerType The listener interface (ActionListener.class, SelectionListener.class, etc.).
130 * @param eventTypes The event types (method names) from the listener interface (if none specified, all will be
131 * supported).
132 */
133 public static <L> void bindEventsToMethod(final Object target, final String methodName, final Object eventSource,
134 final Class<L> listenerType, final String... eventTypes) {
135 final L listener = listenerType.cast(Proxy.newProxyInstance(target.getClass().getClassLoader(),
136 new Class[] { listenerType }, new EventBindingInvocationHandler(target, methodName, eventTypes)));
137 addEventListener(eventSource, listenerType, listener);
138 }
139
140 /**
141 * Make private in 4.0.
142 *
143 * @deprecated TODO Make private in 4.0.
144 */
145 @Deprecated
146 public EventUtils() {
147 // empty
148 }
149 }