import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
import java.io.IOException;
@Configuration
public class JsonConfig {
 @Bean
 @Primary
 @ConditionalOnMissingBean(ObjectMapper.class)
 public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder)
 {
  ObjectMapper objectMapper = builder.createXmlMapper(false).build();
  // 通過(guò)該方法對(duì)mapper對(duì)象進(jìn)行設(shè)置，所有序列化的對(duì)象都將按改規(guī)則進(jìn)行系列化
  // Include.Include.ALWAYS 默認(rèn)
  // Include.NON_DEFAULT 屬性為默認(rèn)值不序列化
  // Include.NON_EMPTY 屬性為 空（""） 或者為 NULL 都不序列化，則返回的json是沒有這個(gè)字段的。這樣對(duì)移動(dòng)端會(huì)更省流量
  // Include.NON_NULL 屬性為NULL 不序列化,就是為null的字段不參加序列化
  //objectMapper.setSerializationInclusion(Include.NON_EMPTY);
  // 字段保留，將null值轉(zhuǎn)為""
  objectMapper.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>()
  {
   @Override
   public void serialize(Object o, JsonGenerator jsonGenerator,
         SerializerProvider serializerProvider)
     throws IOException, JsonProcessingException
   {
    jsonGenerator.writeString("");
   }
  });
  return objectMapper;
 }
}

import java.io.Serializable;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonInclude.Include;
public class RespObject implements Serializable {
  private static final long serialVersionUID = -1560603887556641494L;
  ....
  @JsonInclude(Include.NON_NULL)
  public Object respMsg;
  @JsonInclude(Include.NON_NULL)
  public Object respData;
  ....
}