Jackson的使用

public class User {
    private String name;
    private int age;
    private String gender;
    //如果不加注解的情况下，会转换成为毫秒值
    //@JsonIgnore  这个注解是忽略掉这个属性
    //@JsonIgnore
    @JsonFormat(pattern = "yyyy-MM-dd")
    private Date birthday;


    public User() {
    }

    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 String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
}

 //对于list集合的测试
    @Test
    public void test3() throws Exception {
        //创建一个User对象
        User user = new User();
        user.setName("孙建浩");
        user.setAge(22);
        user.setGender("男");

        user.setBirthday(new Date());

        User user1 = new User();
        user1.setName("孙建浩");
        user1.setAge(22);
        user1.setGender("男");

        user1.setBirthday(new Date());

        User user2 = new User();
        user2.setName("孙建浩");
        user2.setAge(22);
        user2.setGender("男");

        user2.setBirthday(new Date());

        List<User> list = new ArrayList<>();
        list.add(user);
        list.add(user1);
        list.add(user2);

        //创建一个核心Json对象
        ObjectMapper mapper = new ObjectMapper();
        //[{"name":"孙建浩","age":22,"gender":"男","birthday":"2022-04-30"},
        // {"name":"孙建浩","age":22,"gender":"男","birthday":"2022-04-30"},
        // {"name":"孙建浩","age":22,"gender":"男","birthday":"2022-04-30"}]
        System.out.println(mapper.writeValueAsString(list));

    }

    //对于map集合的测试
    @Test
    public void test4() throws Exception {
        //创建一个User对象
        Map<String, Object> map = new HashMap<>();
        map.put("name", "德古拉");
        map.put("age", "888");
        map.put("gender", "nv");

        ObjectMapper mapper = new ObjectMapper();

        //{"gender":"nv","name":"德古拉","age":"888"}
        System.out.println(mapper.writeValueAsString(map));

    }

//json转换成为java对象
    @Test
    public void test5() throws IOException {
        //创建jackSon核心对象
        ObjectMapper mapper = new ObjectMapper();
        String son = "{\"gender\":\"nv\",\"name\":\"德古拉\",\"age\":\"888\"}";
        User user = mapper.readValue(son, User.class); //User{name='德古拉', age=888, gender='nv', birthday=null}
        System.out.println(user);
    }