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
018package org.apache.commons.lang3.event;
019
020import java.lang.reflect.InvocationHandler;
021import java.lang.reflect.InvocationTargetException;
022import java.lang.reflect.Method;
023import java.lang.reflect.Proxy;
024import java.util.Arrays;
025import java.util.HashSet;
026import java.util.Set;
027
028import 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 1606082 2014-06-27 13:03:36Z ggregory $
035 */
036public 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(final Object eventSource, final Class<L> listenerType, final L listener) {
049        try {
050            MethodUtils.invokeMethod(eventSource, "add" + listenerType.getSimpleName(), listener);
051        } catch (final 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 (final 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 (final 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(final Object target, final String methodName, final Object eventSource,
076            final Class<L> listenerType, final 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, final 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        @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                }
115                return MethodUtils.invokeMethod(target, methodName);
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}