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.http.converter; 018 019import java.io.IOException; 020import java.io.UnsupportedEncodingException; 021import java.nio.charset.Charset; 022import java.util.ArrayList; 023import java.util.List; 024 025import org.springframework.http.HttpInputMessage; 026import org.springframework.http.HttpOutputMessage; 027import org.springframework.http.MediaType; 028import org.springframework.util.StreamUtils; 029 030/** 031 * Implementation of {@link HttpMessageConverter} that can read and write strings. 032 * 033 * <p>By default, this converter supports all media types ({@code */*}), 034 * and writes with a {@code Content-Type} of {@code text/plain}. This can be overridden 035 * by setting the {@link #setSupportedMediaTypes supportedMediaTypes} property. 036 * 037 * @author Arjen Poutsma 038 * @author Juergen Hoeller 039 * @since 3.0 040 */ 041public class StringHttpMessageConverter extends AbstractHttpMessageConverter<String> { 042 043 public static final Charset DEFAULT_CHARSET = Charset.forName("ISO-8859-1"); 044 045 046 private volatile List<Charset> availableCharsets; 047 048 private boolean writeAcceptCharset = true; 049 050 051 /** 052 * A default constructor that uses {@code "ISO-8859-1"} as the default charset. 053 * @see #StringHttpMessageConverter(Charset) 054 */ 055 public StringHttpMessageConverter() { 056 this(DEFAULT_CHARSET); 057 } 058 059 /** 060 * A constructor accepting a default charset to use if the requested content 061 * type does not specify one. 062 */ 063 public StringHttpMessageConverter(Charset defaultCharset) { 064 super(defaultCharset, MediaType.TEXT_PLAIN, MediaType.ALL); 065 } 066 067 068 /** 069 * Indicates whether the {@code Accept-Charset} should be written to any outgoing request. 070 * <p>Default is {@code true}. 071 */ 072 public void setWriteAcceptCharset(boolean writeAcceptCharset) { 073 this.writeAcceptCharset = writeAcceptCharset; 074 } 075 076 077 @Override 078 public boolean supports(Class<?> clazz) { 079 return String.class == clazz; 080 } 081 082 @Override 083 protected String readInternal(Class<? extends String> clazz, HttpInputMessage inputMessage) throws IOException { 084 Charset charset = getContentTypeCharset(inputMessage.getHeaders().getContentType()); 085 return StreamUtils.copyToString(inputMessage.getBody(), charset); 086 } 087 088 @Override 089 protected Long getContentLength(String str, MediaType contentType) { 090 Charset charset = getContentTypeCharset(contentType); 091 try { 092 return (long) str.getBytes(charset.name()).length; 093 } 094 catch (UnsupportedEncodingException ex) { 095 // should not occur 096 throw new IllegalStateException(ex); 097 } 098 } 099 100 @Override 101 protected void writeInternal(String str, HttpOutputMessage outputMessage) throws IOException { 102 if (this.writeAcceptCharset) { 103 outputMessage.getHeaders().setAcceptCharset(getAcceptedCharsets()); 104 } 105 Charset charset = getContentTypeCharset(outputMessage.getHeaders().getContentType()); 106 StreamUtils.copy(str, charset, outputMessage.getBody()); 107 } 108 109 110 /** 111 * Return the list of supported {@link Charset}s. 112 * <p>By default, returns {@link Charset#availableCharsets()}. 113 * Can be overridden in subclasses. 114 * @return the list of accepted charsets 115 */ 116 protected List<Charset> getAcceptedCharsets() { 117 if (this.availableCharsets == null) { 118 this.availableCharsets = new ArrayList<Charset>( 119 Charset.availableCharsets().values()); 120 } 121 return this.availableCharsets; 122 } 123 124 private Charset getContentTypeCharset(MediaType contentType) { 125 if (contentType != null && contentType.getCharset() != null) { 126 return contentType.getCharset(); 127 } 128 else { 129 return getDefaultCharset(); 130 } 131 } 132 133}