    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
    018    package org.apache.commons.lang3.event;
    019
    020    import java.lang.reflect.InvocationHandler;
    021    import java.lang.reflect.InvocationTargetException;
    022    import java.lang.reflect.Method;
    023    import java.lang.reflect.Proxy;
    024    import java.util.Arrays;
    025    import java.util.HashSet;
    026    import java.util.Set;
    027
    028    import 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 1091072 2011-04-11 13:42:03Z mbenson $
    035     */
    036    public 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(Object eventSource, Class<L> listenerType, L listener) {
    049            try {
    050                MethodUtils.invokeMethod(eventSource, "add" + listenerType.getSimpleName(), listener);
    051            } catch (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 (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 (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(Object target, String methodName, Object eventSource,
    076                Class<L> listenerType, 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, 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            public Object invoke(final Object proxy, final Method method, final Object[] parameters) throws Throwable {
    110                if (eventTypes.isEmpty() || eventTypes.contains(method.getName())) {
    111                    if (hasMatchingParametersMethod(method)) {
    112                        return MethodUtils.invokeMethod(target, methodName, parameters);
    113                    } else {
    114                        return MethodUtils.invokeMethod(target, methodName);
    115                    }
    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    }