实现 ResponseBodyAdvice 定制化JSON 返回字段

 细粒度定制化JSON返回字段，精确控制每一个接口方法返回的字段

1. 创建注解CustomReturnJson 标注在controller 的方法上。 示例：

    @RequestMapping("/testJson")
    @ResponseBody
    @CustomReturnJson(include = {"id","topicName","topicImg"})
    public Object testJson(@RequestParam("name")String name){
        Topic topic = topicService.getByTopicName(name);
        return ResultVO.success(topic);
    }

只返回 id topicName,topicImg 字段

import java.lang.annotation.*;

/**
 * @author XXX
 * Date: 2019/4/11
 * Description:该注解配合 @ResponseBody 一起使用来细粒度定制返回的json @see {CustomReturnResponseBody.class}
 */
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface CustomReturnJson {

    /**
     * 返回的json包含哪些字段
     */
    String[] include() default {};

}

 2.核心逻辑就是实现 ResponseBodyAdvice  方法beforeBodyWrite ，在json返回前处理

import com.alibaba.druid.support.json.JSONUtils;
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.serializer.BeanContext;
import com.alibaba.fastjson.serializer.ContextValueFilter;
import com.linktime.unitimes.annotation.CustomReturnJson;
import com.linktime.unitimes.vo.ResultVO;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.core.MethodParameter;
import org.springframework.http.MediaType;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.lang.Nullable;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

/**
 * @author liuxun
 * Date: 2019/4/11
 * Description: 用来控制定制化json 返回
 */
@ControllerAdvice
@ConditionalOnProperty(name = "CUSTOM_RETURN_JSON_ADVICE",havingValue = "true")
@Slf4j
public class CustomReturnJsonAdvice implements ResponseBodyAdvice {

    @Override
    public boolean supports(MethodParameter methodParameter, Class aClass) {
        return methodParameter.getMethodAnnotation(CustomReturnJson.class) != null;
    }

    @Nullable
    @Override
    public Object beforeBodyWrite(@Nullable Object body, MethodParameter methodParameter, MediaType mediaType, Class aClass, ServerHttpRequest request, ServerHttpResponse response) {

        if(body != null && body instanceof ResultVO){
            try {

                ResultVO vo = (ResultVO) body;
                Object data = vo.getData();

                CustomReturnJson methodAnnotation = methodParameter.getMethodAnnotation(CustomReturnJson.class);
                String[] include = methodAnnotation.include();
                List<String> collect = Arrays.stream(include).collect(Collectors.toList());

                ContextValueFilter valueFilter = new ContextValueFilter () {
                    @Override
                    public Object process(BeanContext context, Object object, String name, Object value) {
                        if(collect.contains(name)){
                            if(value == null){
                                return "";
                            }
                            return value;
                        }else {
                            return null;
                        }
                    }
                };
                String jsonOutput = JSON.toJSONString(data,valueFilter);
                Object parse = JSONUtils.parse(jsonOutput);
                vo.setData(parse);
                return vo;
            } catch (Exception e) {
                log.error("CustomReturnResponseBody方法出错",e);
                // 如果出错,原样返回。(就当该不存在这个流程)
            }
        }

        return body;
    }

}