springMVC(二)： @RequestBody @ResponseBody 注解实现分析

提示：扫一扫查出行
【扫一扫了解最新限行尾号】
复制提示

一、继承结构

@RequestBody、@ResponseBody的处理器：RequestResponseBodyMethodProcessor

@ModelAttribute处理器： ModelAttributeMethodProcessor

HttpEntity处理器： HttpEntityMethodProcessor

参数值解析器： HandlerMethodArgumentResolver

返回值处理器： HandlerMethodReturnValueHandler

使用HttpMessageConverter 转换方法参数： AbstractMessageConverterMethodArgumentResolver

二、处理过程

1. RequestResponseBodyMethodProcessor的resolveArgument过程

@Override
public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {

//返回@RequestBody需要的参数, Spring使用我们自定义的RequestBodyAdvice, ResponseBodyAdvice发生在这里
Object arg = readWithMessageConverters(webRequest, parameter, parameter.getGenericParameterType());
String name = Conventions.getVariableNameForParameter(parameter);

//输入参数转换成Java对象发生在这里，后面有专门的文章讲解，注意：每次请求绑定的对象的重新生成的
WebDataBinder binder = binderFactory.createBinder(webRequest, arg, name);
if (arg != null) {
validateIfApplicable(binder, parameter);
if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) {
throw new MethodArgumentNotValidException(parameter, binder.getBindingResult());
}
}
mavContainer.addAttribute(BindingResult.MODEL_KEY_PREFIX + name, binder.getBindingResult()); return arg;
} @Override
protected <T> Object readWithMessageConverters(NativeWebRequest webRequest, MethodParameter methodParam,
Type paramType) throws IOException, HttpMediaTypeNotSupportedException, HttpMessageNotReadableException { HttpServletRequest servletRequest = webRequest.getNativeRequest(HttpServletRequest.class);
ServletServerHttpRequest inputMessage = new ServletServerHttpRequest(servletRequest);

//调用父类的readWithMessageCoverters()方法
Object arg = readWithMessageConverters(inputMessage, methodParam, paramType);
if (arg == null) {
if (methodParam.getParameterAnnotation(RequestBody.class).required()) {
throw new HttpMessageNotReadableException("Required request body is missing: " +
methodParam.getMethod().toGenericString());
}
}
return arg;
}