JPA多对多关系导致无限递归和堆栈溢出错误

Question

我正在开发一个EclipseLink项目,其中一个用户可以"关注"另一个用户,这可以在社交媒体网站上完成.我设置了一个User实体(引用一个名为的表users),其中包含一个"关注者"列表(跟随该用户的用户)和另一个"关注"列表(用户正在关注的用户).该关系在一个单独的表中定义,该表followers包含跟随用户的ID(user_id)和以下用户的ID(follower_id)的列.

我的用户模型如下所示:

@Entity
@Table(name = "users")
@NamedQuery(name = "User.findAll", query = "SELECT u FROM USER u")
public class User {
    // other attributes
    @ManyToMany(fetch = FetchType.LAZY)
    @JoinTable(name = "follower", joinColumns = @JoinColumn(
        name = "user_id", referencedColumnName = "id"),
    inverseJoinColumns = @JoinColumn(
        name = "follower_id", referencedColumnName = "id"))
    private List<User> followers;

    @ManyToMany(mappedBy = "followers")
    private List<User> following;

    // other getters and setters
    public List<User> getFollowers() {
        return this.followers;
    }

    public List<User> getFollowing() {
        return this.following;
    }
}

该getFollowers()方法似乎工作正常,但在getFollowing()调用时,我得到一堆控制台垃圾邮件,最终导致StackOverflowException:

com.fasterxml.jackson.databind.JsonMappingException: Infinite recursion 
(StackOverflowError) (through reference chain: 
org.eclipse.persistence.indirection.IndirectList[0]-
>org.myproject.model.User["followers"]-
>org.eclipse.persistence.indirection.IndirectList[0]-
>org.myproject.model.User["following"]-
...
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase
.serializeFields(BeanSerializerBase.java:518)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize
(BeanSerializer.java:117)
at com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer
.serializeContents(IndexedListSerializer.java:94)
at com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer
.serializeContents(IndexedListSerializer.java:21)
...

如果我应该提供更多的堆栈跟踪,请告诉我.任何提示？

Answer 1

每次你有 @OneToMany(一个集合)你需要添加@JsonIgnore它,否则它将导致一个无限循环,导致堆栈溢出异常,因为它一直在父(一方)和孩子(多方)之间查找有关处理此类问题的更多信息,请查看这篇优秀的文章http://www.baeldung.com/jackson-bidirectional-relationships-and-infinite-recursion