2021-10-06

• • JSON对象的类型转换
• 前言
• 一、简单类型转换？
• 二、map复杂情况
• 三、List复杂情况

针对简单类型，有实体类的json，直接转换成单个实体类，对于复杂类型，比如是map形式时，需要进行反序列化。

1.实体类json

public class User {
    private String userName;
    private Integer age;
    private Date createTime;

    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }

    public Date getCreateTime() {
        return addTime;
    }
    public void setCreateTime(Date createTime) {
        this.addTime = addTime;
    }
}

2.进行转化

public class travase {
    public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
        String json = "{"userName":"bob","age":18,"createTime":1991851786568}";
        //这里需要这么写，
        User user = mapper.readValue(json, User.class); //简单类型的时候，这样最方便

        User user1 = mapper.readValue(json, new TypeReference() {}); //这样也可以，TypeReference主要针对复杂类型

        System.out.println(user.getUserName());
        System.out.println(user1.getUserName());
    }
}

public class travase1 {
    public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();

        //注意这里键名和键值都是String类型的
        Map map = new HashMap<>();
        map.put("name", "bob");
        map.put("sex", "男");

        //先生成一个json方便理解
        String json = mapper.writevalueAsString(map);        System.out.println(json);//{"sex":"男","name":"bob"}

        
        Map map1 = new HashMap<>();       
        map1 = mapper.readValue(json, Map.class);
 //map1 = mapper.readValue(json, new TypeReference>() {}); 也可以。并且可以避免在编译时出现的泛型警告问题
        System.out.println(map1.get("name"));
    }
}

1.直接把Json, 转换成 List

public class travase3 {
    public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();

        String json = "[{"userName":"bob","age":18,"createTime":1111}, {"userName":"java","age":19,"createTime":2222}]";

        List list = mapper.readValue(json, List.class);

        System.out.println(list.get(0).getUserName());
    }
}

2.直接转换成 Bean数组

public class travase4 {
    public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();

        String json = "[{"userName":"bob","age":18,"createTime":1111}, {"userName":"java","age":19,"createTime":2222}]";

        Userbase[] userbaseAry = mapper.readValue(json, new TypeReference() {});
                System.out.println(userbaseAry[0].getUserName());
    }
}