从@ManyTomany双向关系中检索数据

Question

我很难找到如何在Spring中从@manytomany关系中检索数据。我遇到了无限递归问题，并尝试了一些解决方案，比如使用@JSONIgnoreProperties，但都没有成功。

一个用户可以有多个组，一个组可以有多个用户。我可以将用户添加到组中，但是当涉及到检索与用户关联的所有组时，我会从无限递归中得到堆栈溢出。

@Entity
public class GroupAccount {

//Private variables omitted for brevity

@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "groupAccount_users",
                joinColumns = {@JoinColumn(name = "groupAccount_id")},
                inverseJoinColumns = {@JoinColumn(name = "user_id")})
private List<User> groupMembers = new ArrayList<>();

//Constructors, most getters, setters omitted for brevity

public void addUserToGroupParticipants(User user){
    groupMembers.add(user);
    incrementGroupMembers();
}

public void incrementGroupMembers() {
    numberOfMembers++;
}

public List<User> getGroupMembers(){
    return groupMembers;
}
}

@Entity
public class User {

//Private variables omitted for brevity

@ManyToMany(mappedBy="groupMembers",
                        fetch = FetchType.LAZY)
private List<GroupAccount> groupAccounts = new ArrayList<>();

//Constructors, most getters, setters omitted for brevity

public List<GroupAccount> getUsersAccounts() {
    return groupAccounts;
}
}

理想情况下，我希望能够发送带有用户ID的get请求，然后检索与该用户关联的所有GroupAccount对象。稍后，我希望能够查看与特定GroupAccount关联的所有用户

Answer 1

您应该在groupmembers上使用@jsonignore注释，以避免陷入无限递归。

@ManyToMany(fetch = FetchType.LAZY)
@JsonIgnore
@JoinTable(name = "groupAccount_users",
                joinColumns = {@JoinColumn(name = "groupAccount_id")},
                inverseJoinColumns = {@JoinColumn(name = "user_id")})
private List<User> groupMembers = new ArrayList<>();