如何将java对象转换成json数据

package cn.hopetesting.com.test;

import cn.hopetesting.com.domain.User;import com.fasterxml.jackson.core.JsonProcessingException;import com.fasterxml.jackson.databind.ObjectMapper;import org.junit.Test;

import java.io.File;import java.io.FileWriter;import java.io.IOException;

/** * @author newcityman * @date 2019/9/17 - 23:12   步骤1、导入jackson的三个包      2、创建一个user对象，并赋值      3、创建jackson的核心对象ObjectMapper      4、调用ObjectMapper的writevalue等相关方法 */public class TestJson {    @Test    public void test1() throws IOException {        //1、创建对象        User user = new User("zmy",20,"male");        //2、创建jackson的核心对象 ObjectMapper        ObjectMapper mapper = new ObjectMapper();        //3、转换        /*try {            String json = mapper.writeValueAsString(user);            System.out.println(json);        } catch (JsonProcessingException e) {            e.printStackTrace();        }*/           //将数据写到d://a.txt文件中//        mapper.writeValue(new File("d://a.txt"),user);        //将数据关联到writer中        mapper.writeValue(new FileWriter("d://b.txt"),user);

    }

    @Test    public void test2() throws IOException {        //1、创建对象        User user = new User("zmy",20,"male");        user.setBirthday(new Date());        //2、创建jackson的核心对象 ObjectMapper        ObjectMapper mapper = new ObjectMapper();        String json = mapper.writeValueAsString(user);        System.out.println(json);

    }

    @Test    public void test3() throws IOException {        //1、创建user和list对象        User user = new User("zmy",20,"male",new Date());        User user1 = new User("light",10,"male",new Date());        User user2 = new User("cityboy",5,"male",new Date());

        List<User> ps = new ArrayList<User>();        ps.add(user);        ps.add(user1);        ps.add(user2);        //2、创建jackson的核心对象 ObjectMapper        ObjectMapper mapper = new ObjectMapper();        String json = mapper.writeValueAsString(ps);        System.out.println(json);

    }

    @Test    public void test4() throws IOException {        Map<String,Object> map = new HashMap<String, Object>();        map.put("name","zmy");        map.put("age",15);        map.put("gender","男");

        ObjectMapper mapper = new ObjectMapper();        String json = mapper.writeValueAsString(map);        System.out.println(json);    }

   //演示 json字符串转换为java对象    @Test    public void test5() throws IOException {        //初始化json字符串       String json="{\"gender\":\"男\",\"name\":\"zmy\",\"age\":15}";       //创建ObjectMapper对象        ObjectMapper mapper = new ObjectMapper();        //转换json字符串为java对象        User user = mapper.readValue(json, User.class);        System.out.println(user);    }}

原文地址：https://www.cnblogs.com/newcityboy/p/11538020.html