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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.lang3.event;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import org.apache.commons.lang3.reflect.MethodUtils;
/**
* Provides some useful event-based utility methods.
*
* @since 3.0
* @version $Id: EventUtils.java 1091072 2011-04-11 13:42:03Z mbenson $
*/
public class EventUtils {
/**
* Adds an event listener to the specified source. This looks for an "add" method corresponding to the event
* type (addActionListener, for example).
* @param eventSource the event source
* @param listenerType the event listener type
* @param listener the listener
* @param the event listener type
*
* @throws IllegalArgumentException if the object doesn't support the listener type
*/
public static void addEventListener(Object eventSource, Class listenerType, L listener) {
try {
MethodUtils.invokeMethod(eventSource, "add" + listenerType.getSimpleName(), listener);
} catch (NoSuchMethodException e) {
throw new IllegalArgumentException("Class " + eventSource.getClass().getName()
+ " does not have a public add" + listenerType.getSimpleName()
+ " method which takes a parameter of type " + listenerType.getName() + ".");
} catch (IllegalAccessException e) {
throw new IllegalArgumentException("Class " + eventSource.getClass().getName()
+ " does not have an accessible add" + listenerType.getSimpleName ()
+ " method which takes a parameter of type " + listenerType.getName() + ".");
} catch (InvocationTargetException e) {
throw new RuntimeException("Unable to add listener.", e.getCause());
}
}
/**
* Binds an event listener to a specific method on a specific object.
*
* @param the event listener type
* @param target the target object
* @param methodName the name of the method to be called
* @param eventSource the object which is generating events (JButton, JList, etc.)
* @param listenerType the listener interface (ActionListener.class, SelectionListener.class, etc.)
* @param eventTypes the event types (method names) from the listener interface (if none specified, all will be
* supported)
*/
public static void bindEventsToMethod(Object target, String methodName, Object eventSource,
Class listenerType, String... eventTypes) {
final L listener = listenerType.cast(Proxy.newProxyInstance(target.getClass().getClassLoader(),
new Class[] { listenerType }, new EventBindingInvocationHandler(target, methodName, eventTypes)));
addEventListener(eventSource, listenerType, listener);
}
private static class EventBindingInvocationHandler implements InvocationHandler {
private final Object target;
private final String methodName;
private final Set eventTypes;
/**
* Creates a new instance of {@code EventBindingInvocationHandler}.
*
* @param target the target object for method invocations
* @param methodName the name of the method to be invoked
* @param eventTypes the names of the supported event types
*/
EventBindingInvocationHandler(final Object target, final String methodName, String[] eventTypes) {
this.target = target;
this.methodName = methodName;
this.eventTypes = new HashSet(Arrays.asList(eventTypes));
}
/**
* Handles a method invocation on the proxy object.
*
* @param proxy the proxy instance
* @param method the method to be invoked
* @param parameters the parameters for the method invocation
* @return the result of the method call
* @throws Throwable if an error occurs
*/
public Object invoke(final Object proxy, final Method method, final Object[] parameters) throws Throwable {
if (eventTypes.isEmpty() || eventTypes.contains(method.getName())) {
if (hasMatchingParametersMethod(method)) {
return MethodUtils.invokeMethod(target, methodName, parameters);
} else {
return MethodUtils.invokeMethod(target, methodName);
}
}
return null;
}
/**
* Checks whether a method for the passed in parameters can be found.
*
* @param method the listener method invoked
* @return a flag whether the parameters could be matched
*/
private boolean hasMatchingParametersMethod(final Method method) {
return MethodUtils.getAccessibleMethod(target.getClass(), methodName, method.getParameterTypes()) != null;
}
}
}
