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 */
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 * Checks 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 Throwable if an error occurs
73 */
74 @Override
75 public Object invoke(final Object proxy, final Method method, final Object[] parameters) throws Throwable {
76 if (eventTypes.isEmpty() || eventTypes.contains(method.getName())) {
77 if (hasMatchingParametersMethod(method)) {
78 return MethodUtils.invokeMethod(target, methodName, parameters);
79 }
80 return MethodUtils.invokeMethod(target, methodName);
81 }
82 return null;
83 }
84 }
85
86 /**
87 * Adds an event listener to the specified source. This looks for an "add" method corresponding to the event
88 * type (addActionListener, for example).
89 * @param eventSource the event source
90 * @param listenerType the event listener type
91 * @param listener the listener
92 * @param <L> the event listener type
93 *
94 * @throws IllegalArgumentException if the object doesn't support the listener type
95 */
96 public static <L> void addEventListener(final Object eventSource, final Class<L> listenerType, final L listener) {
97 try {
98 MethodUtils.invokeMethod(eventSource, "add" + listenerType.getSimpleName(), listener);
99 } catch (final NoSuchMethodException e) {
100 throw new IllegalArgumentException("Class " + eventSource.getClass().getName()
101 + " does not have a public add" + listenerType.getSimpleName()
102 + " method which takes a parameter of type " + listenerType.getName() + ".");
103 } catch (final IllegalAccessException e) {
104 throw new IllegalArgumentException("Class " + eventSource.getClass().getName()
105 + " does not have an accessible add" + listenerType.getSimpleName ()
106 + " method which takes a parameter of type " + listenerType.getName() + ".");
107 } catch (final InvocationTargetException e) {
108 throw new IllegalArgumentException("Unable to add listener.", e.getCause());
109 }
110 }
111
112 /**
113 * Binds an event listener to a specific method on a specific object.
114 *
115 * @param <L> the event listener type
116 * @param target the target object
117 * @param methodName the name of the method to be called
118 * @param eventSource the object which is generating events (JButton, JList, etc.)
119 * @param listenerType the listener interface (ActionListener.class, SelectionListener.class, etc.)
120 * @param eventTypes the event types (method names) from the listener interface (if none specified, all will be
121 * supported)
122 */
123 public static <L> void bindEventsToMethod(final Object target, final String methodName, final Object eventSource,
124 final Class<L> listenerType, final String... eventTypes) {
125 final L listener = listenerType.cast(Proxy.newProxyInstance(target.getClass().getClassLoader(),
126 new Class[] { listenerType }, new EventBindingInvocationHandler(target, methodName, eventTypes)));
127 addEventListener(eventSource, listenerType, listener);
128 }
129 }