Java中关于JSON的基本使用

Java中关于JSON的基本使用

Java中可以操作json的类库jar有很多，网上一找一大片，每种封装的jar包有自己的方法，需要查阅资料使用，但无非就是json转对象，对象转json这些

Java中常见的json类jar包：Gson,Jackson,fastjson

转json：map使用 { } 包围，数组和list使用 [ ] 包围

package demo_json;

import com.google.gson.Gson;
import org.junit.jupiter.api.Test;

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

public class TestJson {

    @Test
    public void testWriteJson(){
        // 实例化Person对象，将Person对象转换为Json串
        Dog dog = new Dog("大力");
        Person person = new Person("liv",10,dog);
        // 将person对象转换成一个字符串 Gson,Jackson,fastjson
        Gson gson = new Gson();
        String jsonStr = gson.toJson(person);//{"name":"liv","age":10,"dog":{"name":"大力"}}
        System.out.println(jsonStr);
    }
    @Test
    public void testReadJson(){
        // 假设jsonStr为json串
        String jsonStr = "{\"name\":\"liv\",\"age\":10,\"dog\":{\"name\":\"大力\"}}";
        // 反序列化Json串为Person
        Gson gson = new Gson();
        Person person = gson.fromJson(jsonStr, Person.class);
        // 获取Person对象的属性值
        System.out.println(person.getName());
        System.out.println(person.getAge());
        System.out.println(person.getDog().getName());
    }
    @Test
    public void testMap(){
        Map data = new HashMap();
        data.put("1","ada");
        data.put("2","dad");
        Gson gson = new Gson();
        String jsonMap = gson.toJson(data);{"1":"ada","2":"dad"}
        System.out.println(jsonMap);
        String mapString = "{\"1\":\"ada\",\"2\":\"dad\"}";
        Map map = gson.fromJson(mapString, Map.class);//{1=ada, 2=dad}
        System.out.println(map);
    }
    @Test
    public void testList(){
        // List 与数组转成json效果一样
        List data = new ArrayList<String>();
        data.add("1");
        data.add("2");
        data.add("3");
        Gson gson = new Gson();
        String json = gson.toJson(data);//["1","2","3"]
        System.out.println(json);
        String[] listString = {"1","2","3"};
        String json1 = gson.toJson(listString);//["1","2","3"]
        System.out.println(json1);

        //对象使用{}包围， list和数组使用[]包围
        Person person = new Person("张三",10,new Dog("大黄"));
        List<Person> persons = new ArrayList<>();
        persons.add(person);
        String json2 = gson.toJson(persons);//[{"name":"张三","age":10,"dog":{"name":"大黄"}}]
        System.out.println(json2);
    }
}

package demo_json;

public class Dog {
    private String name;

    public Dog() {
    }

    public Dog(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

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

package demo_json;

public class Person {
    private String name;
    private int age;
    private Dog dog;

    public Person(String name, int age, Dog dog) {
        this.name = name;
        this.age = age;
        this.dog = dog;
    }

    public Person(){

    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

    public Dog getDog() {
        return dog;
    }

    public void setDog(Dog dog) {
        this.dog = dog;
    }
}