java中的JsonSerializer用法,前后端单位转换必备

public class Date2LongSerializer extends JsonSerializer<Date> {
    @Override
    public void serialize(Date date, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {//把Date转成Long
        jsonGenerator.writeNumber(date.getTime() / 1000);
    }
}

    //创建时间
    @JsonSerialize(using = Date2LongSerializer.class)//时间戳将Date转成Long
    private Date categoryTime;
    //修改时间
    @JsonSerialize(using = Date2LongSerializer.class)
    private Date updateTime;

public class DefaultTimeSerializer extends JsonSerializer<Date> {
   /**
    * Method that can be called to ask implementation to serialize
    * values of type this serializer handles.
    *
    * @param value       Value to serialize; can <b>not</b> be null.
    * @param gen         Generator used to output resulting Json content
    * @param serializers Provider that can be used to get serializers for
    */
   @Override
   public void serialize(Date value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
      if (THOUSAND_MILLISECOND.equals(value.getTime())) {
         gen.writeString("-1");
      } else {
         gen.writeString(DateUtils.dateFormat(value, DateUtils.MONTH_PATTERN));
      }
   }
}

/**
 * 日期(精确到月)
 */
@JsonSerialize(using = DefaultTimeSerializer.class)
private Date Time;