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 beans = ControllerAdviceBean.findAnnotatedBeans(getApplicationContext());
AnnotationAwareOrderComparator.sort(beans);
而ControllerAdviceBean.findAnnotatedBeans方法会查找类上有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.....
