【resttemplate】RestTemplate返回值乱码问题分析与解决 |
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【resttemplate】RestTemplate返回值乱码问题分析与解决
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使用RestTemplate发送请求时，如果接口返回值中包含中文就会出现乱码： RestTemplate restTemplate = new RestTemplate(); String result = restTemplate.getForObject("http://www.baidu.com", String.class); System.out.println(result);运行结果如下： ç™¾åº¦ä¸€ä¸‹ï¼Œä½ å°±çŸ¥é“ æ–°é—» hao123 地图 视频 è´´å§ ç™»å½• document.write('登录'); æ›´å¤šäº§å“ å ³äºŽç™¾åº¦ About Baidu ©2017;Baidu;使用百度å‰å¿ 读; æ„è§å馈;京ICPè¯030173å·; 从源码分析原因 这个问题我首先想到的是RestTemplate的MessageConverter消息转换器，首先找到RestTemplate解析response的地方。 org.springframework.web.client.HttpMessageConverterExtractor#extractData public T extractData(ClientHttpResponse response) throws IOException { MessageBodyClientHttpResponseWrapper responseWrapper = new MessageBodyClientHttpResponseWrapper(response); if (!responseWrapper.hasMessageBody() || responseWrapper.hasEmptyMessageBody()) { return null; } MediaType contentType = getContentType(responseWrapper); try { for (HttpMessageConverter messageConverter : this.messageConverters) { if (messageConverter instanceof GenericHttpMessageConverter) { GenericHttpMessageConverter genericMessageConverter = (GenericHttpMessageConverter) messageConverter; if (genericMessageConverter.canRead(this.responseType, null, contentType)) { if (logger.isDebugEnabled()) { ResolvableType resolvableType = ResolvableType.forType(this.responseType); logger.debug("Reading to [" + resolvableType + "]"); } return (T) genericMessageConverter.read(this.responseType, null, responseWrapper); } } if (this.responseClass != null) { if (messageConverter.canRead(this.responseClass, contentType)) { if (logger.isDebugEnabled()) { String className = this.responseClass.getName(); logger.debug("Reading to [" + className + "] as \"" + contentType + "\""); } return (T) messageConverter.read((Class) this.responseClass, responseWrapper); } } } } catch (IOException | HttpMessageNotReadableException ex) { throw new RestClientException("Error while extracting response for type [" + this.responseType + "] and content type [" + contentType + "]", ex); } throw new UnknownContentTypeException(this.responseType, contentType, response.getRawStatusCode(), response.getStatusText(), response.getHeaders(), getResponseBody(response)); } HttpMessageConverter消息转换器RestTemplate的构造方法中默认内置了下面7个消息转换器： ByteArrayHttpMessageConverterStringHttpMessageConverterResourceHttpMessageConverterSourceHttpMessageConverterAllEncompassingFormHttpMessageConverterJaxb2RootElementHttpMessageConverterMappingJackson2HttpMessageConverter
StringHttpMessageConverter
上面的代码最终会调用StringHttpMessageConverter来对结果进行转换。 canRead()主要根据返回结果的类型和mediaType来进行校验是否可以是否此消息转换器进行转换。 org.springframework.http.converter.AbstractHttpMessageConverter#canRead(java.lang.Class, org.springframework.http.MediaType) public boolean canRead(Class clazz, @Nullable MediaType mediaType) { return supports(clazz) && canRead(mediaType); } public boolean supports(Class clazz) { return String.class == clazz; } protected boolean canRead(@Nullable MediaType mediaType) { if (mediaType == null) { return true; } for (MediaType supportedMediaType : getSupportedMediaTypes()) { if (supportedMediaType.includes(mediaType)) { return true; } } return false; }StringHttpMessageConverter支持restTemplate.getForObject传入的class为String类型，mediaType支持所有，在构造方法中指定了MediaType.ALL public StringHttpMessageConverter() { this(DEFAULT_CHARSET); } /** * A constructor accepting a default charset to use if the requested content * type does not specify one. */ public StringHttpMessageConverter(Charset defaultCharset) { super(defaultCharset, MediaType.TEXT_PLAIN, MediaType.ALL); }当前面的校验通过后，会调用readInternal()对结果进行转换： org.springframework.http.converter.StringHttpMessageConverter#readInternal protected String readInternal(Class clazz, HttpInputMessage inputMessage) throws IOException { Charset charset = getContentTypeCharset(inputMessage.getHeaders().getContentType()); return StreamUtils.copyToString(inputMessage.getBody(), charset); }getContentTypeCharset()会判断使用何种编码方法对结果进行编码，这里使用了默认的编码： org.springframework.http.converter.StringHttpMessageConverter#getContentTypeCharset private Charset getContentTypeCharset(@Nullable MediaType contentType) { if (contentType != null && contentType.getCharset() != null) { return contentType.getCharset(); } else if (contentType != null && (contentType.isCompatibleWith(MediaType.APPLICATION_JSON) || contentType.isCompatibleWith(APPLICATION_PLUS_JSON))) { // Matching to AbstractJackson2HttpMessageConverter#DEFAULT_CHARSET return StandardCharsets.UTF_8; } else { Charset charset = getDefaultCharset(); Assert.state(charset != null, "No default charset"); return charset; } }在StringHttpMessageConverter的构造方法中指定了默认的编码是ISO_8859_1，这就是乱码的根本原因。 public static final Charset DEFAULT_CHARSET = StandardCharsets.ISO_8859_1; public StringHttpMessageConverter() { this(DEFAULT_CHARSET); }我们只要将ISO_8859_1修改为UTF-8就能解决乱码问题。 修改StringHttpMessageConverter的编码方式一：简单粗暴，从源码可得知第一个位置的类型是StringHttpMessageConverter，直接取出来将编码修改为UTF-8。 RestTemplate restTemplate = new RestTemplate(); StringHttpMessageConverter stringHttpMessageConverter = (StringHttpMessageConverter) restTemplate.getMessageConverters().get(1); stringHttpMessageConverter.setDefaultCharset(StandardCharsets.UTF_8); String result = restTemplate.getForObject("http://www.baidu.com", String.class); System.out.println(result);方式二：推荐使用，通过类型来找到StringHttpMessageConverter，将编码修改为UTF-8。 RestTemplate restTemplate = new RestTemplate(); List messageConverters = restTemplate.getMessageConverters(); for (HttpMessageConverter messageConverter : messageConverters) { if(messageConverter instanceof StringHttpMessageConverter) { ((StringHttpMessageConverter) messageConverter).setDefaultCharset(StandardCharsets.UTF_8); } } String result = restTemplate.getForObject("http://www.baidu.com", String.class); System.out.println(result);方式三：将所有的消息转换器的编码都修改为UTF-8 RestTemplate restTemplate = new RestTemplate(); List messageConverters = restTemplate.getMessageConverters(); for (HttpMessageConverter messageConverter : messageConverters) { if(messageConverter instanceof AbstractHttpMessageConverter) { ((AbstractHttpMessageConverter) messageConverter).setDefaultCharset(StandardCharsets.UTF_8); } else if(messageConverter instanceof FormHttpMessageConverter) { ((FormHttpMessageConverter) messageConverter).setCharset(StandardCharsets.UTF_8); ((FormHttpMessageConverter) messageConverter).setMultipartCharset(StandardCharsets.UTF_8); } } String result = restTemplate.getForObject("http://www.baidu.com", String.class); System.out.println(result); MappingJackson2HttpMessageConverter最后来学习一下MappingJackson2HttpMessageConverter，只有MappingJackson2HttpMessageConverter是GenericHttpMessageConverter类型，只有Response的header中的Content-type是application/json才会解析： public MappingJackson2HttpMessageConverter() { this(Jackson2ObjectMapperBuilder.json().build()); } public MappingJackson2HttpMessageConverter(ObjectMapper objectMapper) { super(objectMapper, MediaType.APPLICATION_JSON, new MediaType("application", "*+json")); }MappingJackson2HttpMessageConverter使用了ObjectMapper来进行序列化和反序列化。 |
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