Jackson2多对多反序列化 [英] Jackson2 many to many deserialization

问题描述

我有两个类Event和Users，它们之间具有多对多关系.

I have two classes Events and Users which have a many to many relationship.

public class Event {

    private int id;

  private List<Users> users;
}

public class User {
        private int id;

      private List<Event> events;
}

我已阅读@JsonIdentityInfo批注应该有帮助，但我看不到此类示例.

I have read @JsonIdentityInfo annotation is supposed to help but I cannot see an example of this.

推荐答案

您可以这样在两个类User和Event中使用@JsonIdentityInfo:

You can use @JsonIdentityInfo in the two classes User and Event this way:

import java.util.List;

import com.fasterxml.jackson.annotation.JsonIdentityInfo;
import com.fasterxml.jackson.annotation.ObjectIdGenerators;

@JsonIdentityInfo(generator = ObjectIdGenerators.UUIDGenerator.class, property="@UUID")
public class User
{
    private int id;
    private List<Event> events;

    // Getters and setters
}

...和

import java.util.List;

import com.fasterxml.jackson.annotation.JsonIdentityInfo;
import com.fasterxml.jackson.annotation.ObjectIdGenerators;

@JsonIdentityInfo(generator = ObjectIdGenerators.UUIDGenerator.class, property="@UUID")
public class Event
{
    private int id;
    private List<User> users;

    // Getters and setters
}

您可以根据需要使用任何ObjectIdGenerator.现在，与多对多映射相对应的对象的序列化和反序列化将成功:

You can use any of the ObjectIdGenerators as appropriate. Now, serialization and deserialization of the objects that correspond to the many to many mapping will succeed:

public static void main(String[] args) throws IOException
{
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.configure(SerializationFeature.INDENT_OUTPUT, true);

    Event event1 = new Event();
    event1.setId(1);
    Event event2 = new Event();
    event2.setId(2);

    User user = new User();
    user.setId(10);

    event1.setUsers(Arrays.asList(user));
    event2.setUsers(Arrays.asList(user));
    user.setEvents(Arrays.asList(event1, event2));

    String json = objectMapper.writeValueAsString(user);
    System.out.println(json);

    User deserializedUser = objectMapper.readValue(json, User.class);
    System.out.println(deserializedUser);
}

希望这会有所帮助.

这篇关于Jackson2多对多反序列化的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！