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> 设置拦截器

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) {
 // 自定义拦截器，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;
 }
}

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