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.proxy2.invoker;
019
020import java.io.Serializable;
021import java.lang.reflect.Method;
022
023import org.apache.commons.proxy2.Invoker;
024import org.apache.commons.proxy2.ProxyUtils;
025
026/**
027 * An {@link Invoker} implementation which merely returns null for all method invocations. This class is useful for
028 * scenarios where the "null object" design pattern is needed.
029 * 
030 * @since 1.0
031 */
032public class NullInvoker implements Invoker, Serializable
033{
034    /** Serialization version */
035    private static final long serialVersionUID = 1L;
036
037    /**
038     * Statically available instance.
039     */
040    public static final NullInvoker INSTANCE = new NullInvoker();
041
042    //******************************************************************************************************************
043    // Invoker Implementation
044    //******************************************************************************************************************
045
046    /**
047     * {@inheritDoc}
048     */
049    @Override
050    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable
051    {
052        final Class<?> returnType = method.getReturnType();
053        return ProxyUtils.nullValue(returnType);
054    }
055}