001/*
002 * Copyright 2002-2015 the original  author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.messaging.converter;
018
019import java.util.ArrayList;
020import java.util.Collection;
021import java.util.List;
022
023import org.springframework.messaging.Message;
024import org.springframework.messaging.MessageHeaders;
025import org.springframework.util.Assert;
026
027/**
028 * A {@link MessageConverter} that delegates to a list of registered converters
029 * to be invoked until one of them returns a non-null result.
030 *
031 * <p>As of 4.2.1, this composite converter implements {@link SmartMessageConverter}
032 * in order to support the delegation of conversion hints.
033 *
034 * @author Rossen Stoyanchev
035 * @author Juergen Hoeller
036 * @since 4.0
037 */
038public class CompositeMessageConverter implements SmartMessageConverter {
039
040        private final List<MessageConverter> converters;
041
042
043        /**
044         * Create an instance with the given converters.
045         */
046        public CompositeMessageConverter(Collection<MessageConverter> converters) {
047                Assert.notEmpty(converters, "Converters must not be empty");
048                this.converters = new ArrayList<MessageConverter>(converters);
049        }
050
051
052        @Override
053        public Object fromMessage(Message<?> message, Class<?> targetClass) {
054                for (MessageConverter converter : getConverters()) {
055                        Object result = converter.fromMessage(message, targetClass);
056                        if (result != null) {
057                                return result;
058                        }
059                }
060                return null;
061        }
062
063        @Override
064        public Object fromMessage(Message<?> message, Class<?> targetClass, Object conversionHint) {
065                for (MessageConverter converter : getConverters()) {
066                        Object result = (converter instanceof SmartMessageConverter ?
067                                        ((SmartMessageConverter) converter).fromMessage(message, targetClass, conversionHint) :
068                                        converter.fromMessage(message, targetClass));
069                        if (result != null) {
070                                return result;
071                        }
072                }
073                return null;
074        }
075
076        @Override
077        public Message<?> toMessage(Object payload, MessageHeaders headers) {
078                for (MessageConverter converter : getConverters()) {
079                        Message<?> result = converter.toMessage(payload, headers);
080                        if (result != null) {
081                                return result;
082                        }
083                }
084                return null;
085        }
086
087        @Override
088        public Message<?> toMessage(Object payload, MessageHeaders headers, Object conversionHint) {
089                for (MessageConverter converter : getConverters()) {
090                        Message<?> result = (converter instanceof SmartMessageConverter ?
091                                        ((SmartMessageConverter) converter).toMessage(payload, headers, conversionHint) :
092                                        converter.toMessage(payload, headers));
093                        if (result != null) {
094                                return result;
095                        }
096                }
097                return null;
098        }
099
100
101        /**
102         * Return the underlying list of delegate converters.
103         */
104        public List<MessageConverter> getConverters() {
105                return this.converters;
106        }
107
108        @Override
109        public String toString() {
110                return "CompositeMessageConverter[converters=" + getConverters() + "]";
111        }
112
113}