Jackson2多次反序列化

Question

我有两个类,事件和用户,有很多关系.

public class Event {

    private int id;

  private List<Users> users;
}

public class User {
        private int id;

      private List<Event> events;
}

我已经读过@JsonIdentityInfo注释应该有帮助,但我看不到这个例子.

Answer 1

您可以使用@JsonIdentityInfo在两个类User和Event这种方式:

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一个ObjectIdGenerator.现在,对应于多对多映射的对象的序列化和反序列化将成功:

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);
}

希望这可以帮助.