JSON处理

package com.itheima2;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.Test;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;


public class ObjectMapperTest {

    private ObjectMapper mapper = new ObjectMapper();



    
    @Test
    public void test01() throws Exception {
        ///User对象转json
        User user = new User("张三",23);
        String json = mapper.writeValueAsString(user);
        System.out.println("json字符串:"+json);
        //json转User
        User user2 = mapper.readValue(json,User.class);
        System.out.println("java对象:"+user2);
    }

    
    @Test
    public void test02() throws Exception {
        //json字符串 = {"姓名":"张三","性别":"男"}
        HashMap map = new HashMap<>();
        map.put("姓名:","张三");
        map.put("性别:","男");
        String json = mapper.writeValueAsString(map);
        System.out.println("json字符串:"+json);

        ///  map对象 = {姓名=张三, 性别=男}
        HashMap hashMap = mapper.readValue(json, HashMap.class);
        System.out.println("java对象:"+hashMap);
    }

     
     @Test
     public void test03() throws Exception {
         //json字符串 = {"姓名":"张三","性别":"男"}
         HashMap map = new HashMap<>();
         map.put("黑马一班:", new User("张三",23));
         map.put("黑马二班:",new User("李四",24));
         String json = mapper.writeValueAsString(map);
         System.out.println("json字符串:"+json);

         ///  map对象 = {姓名=张三, 性别=男}
         HashMap hashMap = mapper.readValue(json, new TypeReference>(){}); /// 匿名内部类
         System.out.println("java对象:"+hashMap);
     }

      
      @Test
      public void test04() throws Exception {
          //json字符串 = {"姓名":"张三","性别":"男"}
          ArrayList list = new ArrayList<>();
          list.add("张三");
          list.add("李四");
          String json = mapper.writeValueAsString(list);
          System.out.println("json字符串:"+json);

          ///  map对象 = {姓名=张三, 性别=男}
          ArrayList arrayList = mapper.readValue(json, ArrayList.class);/// 匿名内部类
          System.out.println("java对象:"+arrayList);
      }

       
       @Test
       public void test05() throws Exception {
           //json字符串 = {"姓名":"张三","性别":"男"}
           ArrayList list = new ArrayList<>();
           list.add(new User("张三",23));
           list.add(new User("李四",24));
           String json = mapper.writeValueAsString(list);
           System.out.println("json字符串:"+json);

           ///  map对象 = {姓名=张三, 性别=男}
           ArrayList arrayList = mapper.readValue(json, new TypeReference>(){});/// 匿名内部类
           System.out.println("java对象:"+arrayList);
       }
}

package com.itheima2;

public class User {
    private String name;
    private Integer age;

    public User() {
    }

    public User(String name, Integer age) {
        this.name = name;
        this.age = 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;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + ''' +
                ", age=" + age +
                '}';
    }
}