FastJson实现Date类型转换long类型输出

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.annotation.JSONField;
import lombok.Data;
import java.util.Date;

public class MainClass {

    public static void main(String[] args) {
        Order order = new Order();
        order.setCreateTime(new Date());
        System.out.println(order);
        String s = JSON.toJSONString(order);
        System.out.println(s);
    }
}
@Data
class Order{
    //使用自定义的对象序列化器
    @JSONField(serializeUsing = DateToLong.class)
     private Date createTime;
}

自定义对象序列化器

import java.io.IOException;
import java.lang.reflect.Type;
import java.util.Date;

public class DateToLong implements ObjectSerializer {

    @Override
    public void write(JSONSerializer serializer, Object object, Object fieldName, Type fieldType, int features) throws IOException {
        if(object instanceof Date){
            SerializeWriter out = serializer.out;
            long time=((Date) object).getTime();
            out.writeLong(time);
        }
    }
}