JSON对象与字符串相互转化ObjectMapper

JSON(JavaScript Object Notation) 是一种轻量级的数据交换格式。 易于人阅读和编写。同时也易于机器解析和生成。
对象是一个无序的“‘名称/值’对”集合。一个对象以“{”（左括号）开始，“}”（右括号）结束。每个“名称”后跟一个“:”（冒号）；“‘名称/值’ 对”之间使用“,”（逗号）分隔。

数组是值（value）的有序集合。一个数组以“[”（左中括号）开始，“]”（右中括号）结束。值之间使用“,”（逗号）分隔。

值（value）可以是双引号括起来的字符串（string）、数值(number)、true、false、 null、对象（object）或者数组（array）。这些结构可以嵌套。

        
            com.fasterxml.jackson.core
            jackson-databind
            2.8.5
        

package com.jt.manage.pojo;

public class User {
    private Integer id;
    private String name;
    private Integer age;
    private String sex;
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    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;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + name + ", age=" + age + ", sex=" + sex + "]";
    }
    
}

List uList = objectMapper.readValue(json, new TypeReference>(){});

package objectmapper;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.junit.Test;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.jt.manage.pojo.User;

public class TestObjectMapper {

        //将对象转化为JSON
        @Test
        public void ObjectToJson() throws JsonProcessingException{
            User user=new User();
            user.setId(1);
            user.setName("隔壁老王");
            user.setAge(40);
            user.setSex("男");
            ObjectMapper objectMapper=new ObjectMapper();
            //转化时调用对象的get方法
            String json = objectMapper.writeValueAsString(user);
            System.out.println(json);
            
        }
        @Test
        public void jsonToObject() throws JsonParseException, JsonMappingException, IOException{
            String json="{\"id\":\"1\",\"name\":\"隔壁老王\",\"age\":\"40\",\"sex\":\"男\"}";
            ObjectMapper objectMapper = new ObjectMapper();
            User user = objectMapper.readValue(json, User.class);
            System.out.println(user);
        }
        @Test
        public void jsonOA() throws IOException{
            ListuserList=new ArrayList();
            User user1=new User();
            user1.setId(1);
            user1.setName("隔壁老王");
            user1.setAge(40);
            user1.setSex("男");
            User user2=new User();
            user2.setId(1);
            user2.setName("隔壁老王");
            user2.setAge(40);
            user2.setSex("男");
            userList.add(user1);
            userList.add(user2);
            ObjectMapper objectMapper = new ObjectMapper();
            String json = objectMapper.writeValueAsString(userList);
            System.out.println("获取JSON串"+json);
            //将复杂格式的JSON转化为对象List
            List uList = objectMapper.readValue(json, userList.getClass());
            System.out.println("获取对象"+uList);
            User[] users = objectMapper.readValue(json, User[].class);
            //将数组转化为List集合
            List uList2=Arrays.asList(users);
            System.out.println("获取对象"+uList2);
        }

}

获取JSON串[{"id":1,"name":"隔壁老王","age":40,"sex":"男"},{"id":1,"name":"隔壁老王","age":40,"sex":"男"}]
获取对象[{id=1, name=隔壁老王, age=40, sex=男}, {id=1, name=隔壁老王, age=40, sex=男}]
获取对象[User [id=1, name=隔壁老王, age=40, sex=男], User [id=1, name=隔壁老王, age=40, sex=男]]