001/*
002 * Copyright 2002-2017 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.nio.charset.Charset;
020import java.nio.charset.StandardCharsets;
021
022import org.springframework.lang.Nullable;
023import org.springframework.messaging.Message;
024import org.springframework.messaging.MessageHeaders;
025import org.springframework.util.Assert;
026import org.springframework.util.MimeType;
027
028/**
029 * A {@link MessageConverter} that supports MIME type "text/plain" with the
030 * payload converted to and from a String.
031 *
032 * @author Rossen Stoyanchev
033 * @since 4.0
034 */
035public class StringMessageConverter extends AbstractMessageConverter {
036
037        private final Charset defaultCharset;
038
039
040        public StringMessageConverter() {
041                this(StandardCharsets.UTF_8);
042        }
043
044        public StringMessageConverter(Charset defaultCharset) {
045                super(new MimeType("text", "plain", defaultCharset));
046                Assert.notNull(defaultCharset, "Default Charset must not be null");
047                this.defaultCharset = defaultCharset;
048        }
049
050
051        @Override
052        protected boolean supports(Class<?> clazz) {
053                return (String.class == clazz);
054        }
055
056        @Override
057        protected Object convertFromInternal(Message<?> message, Class<?> targetClass, @Nullable Object conversionHint) {
058                Charset charset = getContentTypeCharset(getMimeType(message.getHeaders()));
059                Object payload = message.getPayload();
060                return (payload instanceof String ? payload : new String((byte[]) payload, charset));
061        }
062
063        @Override
064        @Nullable
065        protected Object convertToInternal(
066                        Object payload, @Nullable MessageHeaders headers, @Nullable Object conversionHint) {
067
068                if (byte[].class == getSerializedPayloadClass()) {
069                        Charset charset = getContentTypeCharset(getMimeType(headers));
070                        payload = ((String) payload).getBytes(charset);
071                }
072                return payload;
073        }
074
075        private Charset getContentTypeCharset(@Nullable MimeType mimeType) {
076                if (mimeType != null && mimeType.getCharset() != null) {
077                        return mimeType.getCharset();
078                }
079                else {
080                        return this.defaultCharset;
081                }
082        }
083
084}