深入浅析JSON在java中的使用

public class Person {
    private Integer id;
    private String name;

    public Person() {
    }

    public Person(Integer id, String name) {
        this.id = id;
        this.name = name;
    }

    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;
    }

    @Override
    public String toString() {
        return "Person{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }

}

 @Test
    public void test1(){
        Person person = new Person(1, "张三");

        Gson gson = new Gson();

        String personJsonToString = gson.toJson(person);        //toJson()方法可以把java对象转换成json字符串

        System.out.println(personJsonToString);

        Person person1 = gson.fromJson(personJsonToString, Person.class);//fromJson()方法可以把json字符串转换成java对象

        System.out.println(person1);
    }

public class PersonListType extends TypeToken<ArrayList<Person>> {
}

 @Test
    public void test2(){

        ArrayList<Person> personArrayList = new ArrayList<>();

        personArrayList.add(new Person(1,"张三"));
        personArrayList.add(new Person(2,"李四"));
        personArrayList.add(new Person(3,"王五"));

        Gson gson = new Gson();

        //把List转换为json字符串
        String personListToString = gson.toJson(personArrayList);
        System.out.println(personListToString);

        //把json字符串祝转化成List
        List<Person> list = gson.fromJson(personListToString, new PersonListType().getType());
        System.out.println(list);
        Person person = list.get(0);
        System.out.println(person);
    }

 //List<Person> list = gson.fromJson(personListToString, new PersonListType().getType());
        List<Person> list = gson.fromJson(personListToString, personArrayList.getClass());
        System.out.println(list);
        System.out.println(list.get(0) instanceof Person);
        System.out.println(list.get(0) instanceof List);
        System.out.println(list.get(0) instanceof Map);

        Person person = list.get(0);
        System.out.println(person);

//TypeToken是泛型类，List<Person>、或者具体的ArrayList<Person>都可以
public class PersonListType extends TypeToken<ArrayList<Person>> {

}

 List<Person> list = gson.fromJson(personListToString, new PersonListType().getType());
        //List<Person> list = gson.fromJson(personListToString, personArrayList.getClass());
        System.out.println(list);
        System.out.println(list.get(0) instanceof Person);
        System.out.println(list.get(0) instanceof List);
        System.out.println(list.get(0) instanceof Map);

        Person person = list.get(0);
        System.out.println(person);

public class PersonMapType extends TypeToken<HashMap<Integer, Person>>{
}

@Test
    public void test3(){

        Map<Integer,Person> map = new HashMap<Integer,Person>();

        map.put(1,new Person(1,"张三"));
        map.put(2,new Person(2,"李四"));

        Gson gson = new Gson();

        //把map集合转换成为json字符串
        String personMapJsonString = gson.toJson(map);
        System.out.println(personMapJsonString);

        //把json字符串转换成map集合
        Map<Integer,Person> personMap1 = gson.fromJson(personMapJsonString, new PersonMapType().getType());
        System.out.println(personMap1);
        Person person = personMap1.get(1);
        System.out.println(person);

    }