SpringMVC對出參和入?yún)⒂蟹浅Ｓ押玫耐卣怪С?方便你對數(shù)據(jù)的輸入和輸出有更大的執(zhí)行權(quán)，我們?nèi)绾瓮ㄟ^SpringMVC定義的結(jié)果做一系列處理呢？

入?yún)?/h3>

RequestBodyAdvice : 針對所有以@RequestBody的參數(shù)做處理

參考案例 : JsonViewRequestBodyAdvice

public class JsonViewRequestBodyAdvice extends RequestBodyAdviceAdapter {

    /**
     * 這里是一個前置攔截匹配操作,其實就是告訴你滿足為true的才會執(zhí)行下面的beforeBodyRead方法,這里可以定義自己業(yè)務(wù)相關(guān)的攔截匹配
     * @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);
    }

        // 這里就是具體的前置操作了... 下面的例子就是查找這個入?yún)⒎椒ㄊ欠裼蠤JsonView修飾
    @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]);
    }

}

出參

ResponseBodyAdvice: 針對所有以@ResponseBody的參數(shù)做處理

參考案例:

@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 就是返回的結(jié)果對象,沒有處理之前
        return body; 
    }
}

注意事項

自定義的處理對象類上必須得加上@ControllerAdvice注解!
為什么?
源碼中RequestMappingHandlerAdapter類在執(zhí)行initControllerAdviceCache()做初始化的時候會執(zhí)行一個

List<ControllerAdviceBean> beans = ControllerAdviceBean.findAnnotatedBeans(getApplicationContext());
AnnotationAwareOrderComparator.sort(beans);

而ControllerAdviceBean.findAnnotatedBeans方法會查找類上有ControllerAdvice注解的類才會加入到處理當(dāng)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;
    }

所以大家可以根據(jù)自己的需要,定義結(jié)果的入?yún)⒑统鰠⒔Y(jié)果做一些特殊處理.....