SpringBoot ResponseBody返回值处理的实现

1. SpringBoot ResponseBody 返回值中null值处理

@PostMapping(path = "/test", produces = MediaType.APPLICATION_JSON_VALUE)
public Object test() {
JSONObject jsonObject = new JSONObject();
jsonObject.put("test","test");
jsonObject.put("testnull",null);
ApiResponseVo apiResponseVo = new ApiResponseVo();
apiResponseVo.setData(jsonObject );
apiResponseVo.setStatus(0);
return apiResponseVo;
}

接口返回 (想实现将testnull也进行返回<null展示null还是0还是"" 可自定义>) :

{
 "data": {
   "test": "test"
 },
 "status": 0
}

import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;
import com.alibaba.fastjson.serializer.SerializerFeature;
import com.alibaba.fastjson.support.config.FastJsonConfig;
import com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter;
@Configuration
public class fastJsonConfig extends WebMvcConfigurationSupport {
@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();
FastJsonConfig config = new FastJsonConfig();
config.setSerializerFeatures(
 // 保留 Map 空的字段
 SerializerFeature.WriteMapNullValue,
 // 将 String 类型的 null 转成""
//        SerializerFeature.WriteNullStringAsEmpty,
       // 将 Number 类型的 null 转成 0
//        SerializerFeature.WriteNullNumberAsZero,
       // 将 List 类型的 null 转成 []
//        SerializerFeature.WriteNullListAsEmpty,
       // 将 Boolean 类型的 null 转成 false
//        SerializerFeature.WriteNullBooleanAsFalse,
 // 避免循环引用
 SerializerFeature.DisableCircularReferenceDetect
);
converter.setFastJsonConfig(config);
converter.setDefaultCharset(Charset.forName("UTF-8"));
List<MediaType> mediaTypeList = new ArrayList<>();
// 解决中文乱码问题，相当于在 Controller 上的 @RequestMapping 中加了个属性 produces = "application/json"
mediaTypeList.add(MediaType.APPLICATION_JSON);
converter.setSupportedMediaTypes(mediaTypeList);
converters.add(converter);
}
}

2. 拦截responsebody转json,对数据进行二次处理 (字典转换做案例)

2.1> 设置 *

import java.nio.charset.StandardCharsets;
import java.util.List;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.StringHttpMessageConverter;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import com.alibaba.fastjson.serializer.SerializerFeature;
import com.alibaba.fastjson.support.config.FastJsonConfig;
import com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter;
import com.fintell.dp3.manager.interceptor.LogInterceptor;
@Configuration
public class WebMvcConfiguration implements WebMvcConfigurer {
@Override
public void addInterceptors(InterceptorRegistry registry) {
// 自定义 * ，添加拦截路径和排除拦截路径
registry.addInterceptor(getLogInterceptor()).addPathPatterns("/**");
}
@Bean
public LogInterceptor getLogInterceptor() {
return new LogInterceptor();
}
/**
* 修改StringHttpMessageConverter默认配置 & Json 默认序列化方式 (改这个方法)
*/
@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
  //创建fastJson消息转换器
  FastJsonHttpMessageConverter fastConverter = new FastJsonHttpMessageConverter();
  //创建配置类
  FastJsonConfig fastJsonConfig = new FastJsonConfig();
  //修改配置返回内容的过滤
  fastJsonConfig.setSerializerFeatures(
      SerializerFeature.DisableCircularReferenceDetect,
      SerializerFeature.WriteMapNullValue,
      SerializerFeature.WriteNullStringAsEmpty
  );
  fastConverter.setFastJsonConfig(fastJsonConfig);
  //将fastjson添加到视图消息转换器列表内
  converters.add(fastConverter);
}
}

 2.2> 字典注解类

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface Dict {
String type();
}

2.3> 序列化类

import java.io.IOException;
import java.lang.reflect.Field;
import org.apache.commons.lang3.StringUtils;
import org.springframework.context.annotation.Configuration;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;
import lombok.extern.slf4j.Slf4j;
@Slf4j
@Configuration
public class DictJsonSerializer extends JsonSerializer<Object> {
@Override
 public void serialize(Object dictVal, JsonGenerator generator, SerializerProvider provider) throws IOException {
  ObjectMapper objectMapper = new ObjectMapper();
   String currentName = generator.getOutputContext().getCurrentName();
   try {
     // 1> 获取字段
     Field field = generator.getCurrentValue().getClass().getDeclaredField(currentName);
     // 2> 获取字典注解
     Dict dict = field.getDeclaredAnnotation(Dict.class);
     // 3> 判断是否添加了字典注解
     if(dict == null) {
      objectMapper.writeValue(generator, dictVal);
      return;
     }
     // 4> 获取注解的type值
     String type = dict.type();
     // **************** 以下依据实际业务处理即可 ********************
     // 5> 获取到字段的值
     String val = dictVal == null ? "" : dictVal.toString();
     String dictValName = "";
     if(!StringUtils.isEmpty(val)) {
       // 6> 这里可以依据type做不同的处理逻辑
      dictValName = "通过自己的方法,依据val获取到对应的字典值";
     }
     // 7> 将字段改写为{"code":"code","name":"name"}格式
     objectMapper.writeValue(generator, BaseEnum.builder().code(dictVal).name(dictValName.toString()).build());
   } catch (NoSuchFieldException e) {
    log.error(e);
   }
 }
}

2.4> 字典注解使用

@SuppressWarnings("serial")
@Builder
@Getter
@Setter
@ToString
@NoArgsConstructor
@AllArgsConstructor
public class BizRuleDto implements Serializable{
 // 指定使用哪种序列化
 @JsonSerialize(using = DictJsonSerializer.class)
 // 指定字典 (将被转换为{"code":"content","name":"contentname"}格式)
 @Dict(type = "content")
private String content;
}

3. 其它补充 (从容器中获取某个实例) : 如 DictJsonSerializer 需要通过service查询数据库获取字典

@Slf4j
public class DictJsonSerializer extends JsonSerializer<Object> {
 // service
private static ProductProxy productProxy;
static {
productProxy = SpringUtils.getBean(ProductProxy.class);
}
 @Override
 public void serialize(Object dictVal, JsonGenerator generator, SerializerProvider provider) throws IOException {
 }
}

SpringUtils

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;
@Component
public class SpringUtils implements ApplicationContextAware {
private static ApplicationContext ctx;
/**
* 获取bean
*/
@SuppressWarnings("unchecked")
public static <T> T getBean(String id) {
return (T) ctx.getBean(id);
}
/**
* 按类型获取bean
*/
public static <T> T getBean(Class<T> clazz) {
return ctx.getBean(clazz);
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
ctx = applicationContext;
}
}

来源：https://blog.csdn.net/qq_17522211/article/details/103886918