RequestBodyAdvice和ResponseBodyAdvice

RequestBodyAdvice和ResponseBodyAdvice

这是spring 4.2新加的两个接口，这两个接口有些什么作用呢？先看看这两个接口

RequestBodyAdvice

public interface RequestBodyAdvice {    boolean supports(MethodParameter methodParameter, Type targetType,            Class<? extends HttpMessageConverter<?>> converterType);    Object handleEmptyBody(Object body, HttpInputMessage inputMessage, MethodParameter parameter,            Type targetType, Class<? extends HttpMessageConverter<?>> converterType);    HttpInputMessage beforeBodyRead(HttpInputMessage inputMessage, MethodParameter parameter,            Type targetType, Class<? extends HttpMessageConverter<?>> converterType) throws IOException;    Object afterBodyRead(Object body, HttpInputMessage inputMessage, MethodParameter parameter,            Type targetType, Class<? extends HttpMessageConverter<?>> converterType);}

查看一下谁调用了这个接口的这些方法，可以看到AbstractMessageConverterMethodArgumentResolver的readWithMessageConverters()方法调用了这个接口的方法。

//代码片段for (HttpMessageConverter<?> converter : this.messageConverters) {            Class<HttpMessageConverter<?>> converterType = (Class<HttpMessageConverter<?>>) converter.getClass();            if (converter instanceof GenericHttpMessageConverter) {                GenericHttpMessageConverter<?> genericConverter = (GenericHttpMessageConverter<?>) converter;                if (genericConverter.canRead(targetType, contextClass, contentType)) {                    if (logger.isDebugEnabled()) {                        logger.debug("Read [" + targetType + "] as \"" + contentType + "\" with [" + converter + "]");                    }                    if (inputMessage.getBody() != null) {                        inputMessage = getAdvice().beforeBodyRead(inputMessage, param, targetType, converterType);                        body = genericConverter.read(targetType, contextClass, inputMessage);                        body = getAdvice().afterBodyRead(body, inputMessage, param, targetType, converterType);                    }                    else {                        body = null;                        body = getAdvice().handleEmptyBody(body, inputMessage, param, targetType, converterType);                    }                    break;                }            }

可以看到这接口的方法，主要是在HttpMessageConverter处理request body的前后做一些处理，和body为空的时候做处理。
而AbstractMessageConverterMethodArgumentResolver的实现类有
HttpEntityMethodProcessor(处理controller的方法参数是HttpEntity或RequestEntity的)、
RequestResponseBodyMethodProcessor(处理方法参数有@RequestBoyd的)、
RequestPartMethodArgumentResolver(处理方法参数是@RequestPart或MultipartFile,javax.servlet.http.Part)。

从这个可以看出，我们可以在使用这些HandlerMethodArgumentResolver的时候，我们能对request body进行前处理，和解析后处理。

RequestBodyAdvice怎么用

首先一个实现类，实现RequestBodyAdvice，后在类上加上注解@ControllerAdvice，比如有些请求的参数需要做加密处理，可以在此将json串解密处理，在处理

ResponseBodyAdvice

public interface ResponseBodyAdvice<T> {boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType);T beforeBodyWrite(T body, MethodParameter returnType, MediaType selectedContentType,        Class<? extends HttpMessageConverter<?>> selectedConverterType,        ServerHttpRequest request, ServerHttpResponse response);}

此可以对@ResponseBody的返回结果在输出到响应之前做处理