001/*
002 * Copyright 2002-2016 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.http.converter;
018
019import java.io.IOException;
020import java.nio.charset.Charset;
021
022import org.springframework.core.convert.ConversionService;
023import org.springframework.http.HttpInputMessage;
024import org.springframework.http.HttpOutputMessage;
025import org.springframework.http.MediaType;
026import org.springframework.util.Assert;
027
028/**
029 * An {@code HttpMessageConverter} that uses {@link StringHttpMessageConverter}
030 * for reading and writing content and a {@link ConversionService} for converting
031 * the String content to and from the target object type.
032 *
033 * <p>By default, this converter supports the media type {@code text/plain} only.
034 * This can be overridden through the {@link #setSupportedMediaTypes supportedMediaTypes}
035 * property.
036 *
037 * <p>A usage example:
038 *
039 * <pre class="code">
040 * &lt;bean class="org.springframework.http.converter.ObjectToStringHttpMessageConverter">
041 *   &lt;constructor-arg>
042 *     &lt;bean class="org.springframework.context.support.ConversionServiceFactoryBean"/>
043 *   &lt;/constructor-arg>
044 * &lt;/bean>
045 * </pre>
046 *
047 * @author <a href="mailto:dmitry.katsubo@gmail.com">Dmitry Katsubo</a>
048 * @author Rossen Stoyanchev
049 * @since 3.2
050 */
051public class ObjectToStringHttpMessageConverter extends AbstractHttpMessageConverter<Object> {
052
053        private final ConversionService conversionService;
054
055        private final StringHttpMessageConverter stringHttpMessageConverter;
056
057
058        /**
059         * A constructor accepting a {@code ConversionService} to use to convert the
060         * (String) message body to/from the target class type. This constructor uses
061         * {@link StringHttpMessageConverter#DEFAULT_CHARSET} as the default charset.
062         * @param conversionService the conversion service
063         */
064        public ObjectToStringHttpMessageConverter(ConversionService conversionService) {
065                this(conversionService, StringHttpMessageConverter.DEFAULT_CHARSET);
066        }
067
068        /**
069         * A constructor accepting a {@code ConversionService} as well as a default charset.
070         * @param conversionService the conversion service
071         * @param defaultCharset the default charset
072         */
073        public ObjectToStringHttpMessageConverter(ConversionService conversionService, Charset defaultCharset) {
074                super(defaultCharset, MediaType.TEXT_PLAIN);
075
076                Assert.notNull(conversionService, "ConversionService is required");
077                this.conversionService = conversionService;
078                this.stringHttpMessageConverter = new StringHttpMessageConverter(defaultCharset);
079        }
080
081
082        /**
083         * Indicates whether the {@code Accept-Charset} should be written to any outgoing request.
084         * <p>Default is {@code true}.
085         */
086        public void setWriteAcceptCharset(boolean writeAcceptCharset) {
087                this.stringHttpMessageConverter.setWriteAcceptCharset(writeAcceptCharset);
088        }
089
090
091        @Override
092        public boolean canRead(Class<?> clazz, MediaType mediaType) {
093                return this.conversionService.canConvert(String.class, clazz) && canRead(mediaType);
094        }
095
096        @Override
097        public boolean canWrite(Class<?> clazz, MediaType mediaType) {
098                return this.conversionService.canConvert(clazz, String.class) && canWrite(mediaType);
099        }
100
101        @Override
102        protected boolean supports(Class<?> clazz) {
103                // should not be called, since we override canRead/Write
104                throw new UnsupportedOperationException();
105        }
106
107        @Override
108        protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage) throws IOException {
109                String value = this.stringHttpMessageConverter.readInternal(String.class, inputMessage);
110                return this.conversionService.convert(value, clazz);
111        }
112
113        @Override
114        protected void writeInternal(Object obj, HttpOutputMessage outputMessage) throws IOException {
115                String value = this.conversionService.convert(obj, String.class);
116                this.stringHttpMessageConverter.writeInternal(value, outputMessage);
117        }
118
119        @Override
120        protected Long getContentLength(Object obj, MediaType contentType) {
121                String value = this.conversionService.convert(obj, String.class);
122                return this.stringHttpMessageConverter.getContentLength(value, contentType);
123        }
124
125}