SpringMVC的Body参数拦截
SpringMVC对出参和入参有非常友好的拓展支持,方便你对数据的输入和输出有更大的执行权，我们如何通过SpringMVC定义的结果做一系列处理呢？
入参
RequestBodyAdvice : 针对所有以@RequestBody的参数做处理
参考案例 : JsonViewRequestBodyAdvice
public class JsonViewRequestBodyAdvice extends RequestBodyAdviceAdapter { /** * 这里是一个前置拦截匹配操作,其实就是告诉你满足为true的才会执行下面的beforeBodyRead方法,这里可以定义自己业务相关的拦截匹配 * @param methodParameter * @param targetType * @param converterType * @return */ @Override public boolean supports(MethodParameter methodParameter, Type targetType, Class<? extends HttpMessageConverter<?>> converterType) { return (AbstractJackson2HttpMessageConverter.class.isAssignableFrom(converterType) && methodParameter.getParameterAnnotation(JsonView.class) != null); } // 这里就是具体的前置操作了... 下面的例子就是查找这个入参方法是否有@JsonView修饰 @Override public HttpInputMessage beforeBodyRead(HttpInputMessage inputMessage, MethodParameter methodParameter, Type targetType, Class<? extends HttpMessageConverter<?>> selectedConverterType) throws IOException { JsonView annotation = methodParameter.getParameterAnnotation(JsonView.class); Class<?>[] classes = annotation.value(); if (classes.length != 1) { throw new IllegalArgumentException( "@JsonView only supported for request body advice with exactly 1 class argument: " + methodParameter); } return new MappingJacksonInputMessage(inputMessage.getBody(), inputMessage.getHeaders(), classes[0]); } }
出参
ResponseBodyAdvice: 针对所有以@ResponseBody的参数做处理
参考案例:
@ControllerAdvice public class LogResponseBodyAdvice implements ResponseBodyAdvice { /** * * @param returnType * @param converterType * @return */ @Override public boolean supports(MethodParameter returnType, Class converterType) { return true; } @Override public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType, Class selectedConverterType, ServerHttpRequest request, ServerHttpResponse response) { // 做任何事情 body 就是返回的结果对象,没有处理之前 return body; } }
注意事项
自定义的处理对象类上必须得加上@ControllerAdvice注解!
为什么?
源码中RequestMappingHandlerAdapter类在执行initControllerAdviceCache()做初始化的时候会执行一个
List<ControllerAdviceBean> beans = ControllerAdviceBean.findAnnotatedBeans(getApplicationContext()); AnnotationAwareOrderComparator.sort(beans);
而ControllerAdviceBean.findAnnotatedBeans方***查找类上有ControllerAdvice注解的类才会加入到处理当中..
public static List<ControllerAdviceBean> findAnnotatedBeans(ApplicationContext applicationContext) { List<ControllerAdviceBean> beans = new ArrayList<ControllerAdviceBean>(); for (String name : BeanFactoryUtils.beanNamesForTypeIncludingAncestors(applicationContext, Object.class)) { if (applicationContext.findAnnotationOnBean(name, ControllerAdvice.class) != null) { beans.add(new ControllerAdviceBean(name, applicationContext)); } } return beans; }
所以大家可以根据自己的需要,定义结果的入参和出参结果做一些特殊处理.....
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