JackSon 动态为 JSON 数据添加字段

package com.example.demo;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;

/**
 * @author Dongguabai
 * @description
 * @date 2021-03-19 10:51
 */
public class Test2222 {

    public static void main(String[] args) throws JsonProcessingException {
        User user = new User();
        user.setName("zhangsan");
        user.setAge(10);
        ObjectMapper objectMapper = new ObjectMapper();
        String jsonStr = objectMapper.writeValueAsString(user);
        ObjectNode objectNode = (ObjectNode) objectMapper.readTree(jsonStr);
        objectNode.put("message", 123);

        String newJsonStr = objectNode.toString();
        System.out.println("之前的json：" + jsonStr);
        System.out.println("新的JSON：" + newJsonStr);
    }
}

class User {
    private String name;

    private Integer age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }
}

输出结果：

之前的json：{"name":"zhangsan","age":10}
新的JSON：{"name":"zhangsan","age":10,"message":123}