001package ball.lang.reflect;
002/*-
003 * ##########################################################################
004 * Utilities
005 * $Id: InterceptingInvocationHandler.java 7215 2021-01-03 18:39:51Z ball $
006 * $HeadURL: svn+ssh://svn.hcf.dev/var/spool/scm/repository.svn/ball-util/trunk/src/main/java/ball/lang/reflect/InterceptingInvocationHandler.java $
007 * %%
008 * Copyright (C) 2008 - 2021 Allen D. Ball
009 * %%
010 * Licensed under the Apache License, Version 2.0 (the "License");
011 * you may not use this file except in compliance with the License.
012 * You may obtain a copy of the License at
013 *
014 *      http://www.apache.org/licenses/LICENSE-2.0
015 *
016 * Unless required by applicable law or agreed to in writing, software
017 * distributed under the License is distributed on an "AS IS" BASIS,
018 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
019 * See the License for the specific language governing permissions and
020 * limitations under the License.
021 * ##########################################################################
022 */
023import java.lang.reflect.Method;
024import lombok.Getter;
025import lombok.RequiredArgsConstructor;
026import lombok.ToString;
027
028import static org.apache.commons.lang3.reflect.MethodUtils.invokeMethod;
029
030/**
031 * "Intercepting" {@link java.lang.reflect.InvocationHandler}
032 * implementation.
033 *
034 * @param       <T>     The type of the "wrapped" target.
035 *
036 * {@bean.info}
037 *
038 * @author {@link.uri mailto:ball@hcf.dev Allen D. Ball}
039 * @version $Revision: 7215 $
040 */
041@RequiredArgsConstructor @ToString
042public class InterceptingInvocationHandler<T> extends DefaultInvocationHandler {
043    @Getter private final T target;
044
045    /**
046     * Subclasses may declare methods with the same signature of a proxied
047     * interface method which will be invoked (as a sort of listener) before
048     * invoking the target method.  If the invoked {@link Method}'s
049     * declaring class is assignable from the target's class, the
050     * {@link Method} is invoked on the target.
051     *
052     * @param   proxy           The proxy instance.
053     * @param   method          The {@link Method}.
054     * @param   argv            The argument array.
055     *
056     * @return  The value to return from the {@link Method} invocation.
057     *
058     * @throws  Exception       If the {@link Method} cannot be invoked.
059     */
060    @Override
061    public Object invoke(Object proxy, Method method, Object[] argv) throws Throwable {
062        try {
063            invokeMethod(this, true,
064                         method.getName(),
065                         argv, method.getParameterTypes());
066        } catch (Exception exception) {
067        }
068
069        Object result = null;
070
071        if (method.isDefault()) {
072            result = super.invoke(proxy, method, argv);
073        } else if (method.getDeclaringClass().isAssignableFrom(target.getClass())) {
074            result = method.invoke(target, argv);
075        } else {
076            result = super.invoke(proxy, method, argv);
077        }
078
079        return result;
080    }
081}