Hibernate：一对多映射导致循环对象

Posted 2023-02-26

【中文标题】Hibernate：一对多映射导致循环对象

【英文标题】：Hibernate: One to many mapping is leading to circular objects

【发布时间】：2021-03-13 01:02:52

【问题描述】：

我有一个用例，一个用户可以拥有多个房子。这就是模型的样子 应用程序用户.java

 @Getter
 @Setter
 @Entity
 public class ApplicationUser 
 @Id
 @GeneratedValue(strategy = GenerationType.SEQUENCE)
private long id;

@Column(nullable = false, unique = true)
private String username;

@Column(nullable = false)
@JsonProperty(access = JsonProperty.Access.WRITE_ONLY)
private String password;

@Column(nullable = false)
private String emailId;

@OneToMany(fetch = FetchType.LAZY, mappedBy = "applicationUser", cascade = CascadeType.REMOVE)
private List<House> houses;

House.Java

@Getter
@Setter
@Entity
public class House 
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE)
private long id;

@ManyToOne()
@JoinColumn(name = "application_user")
private ApplicationUser applicationUser;

@Column(name = "House_Name")
private String houseName;

HouseRepository

public interface HouseRepository extends JpaRepository<House, Long> 
    public House findByHouseName(String houseName);

    public List<House> findAllByApplicationUser_Username(String userName);

每当我尝试检索任何房子时，房子对象都包含用户对象，而用户对象又包含房子对象。这会无限进行。

    "id": 3,
    "applicationUser": 
        "id": 2,
        "username": "test",
        "emailId": "testmail",
        "houses": [
            
                "id": 3,
                "applicationUser": 
                    "id": 2,
                    "username": "test",
                    "emailId": "testmail",
                    "houses": [
                        
                            "id": 3,
                            "applicationUser": 
                                "id": 2,
                                "username": "test",
                                "emailId": "testmail",
                                "houses": [

我该如何阻止这种情况发生？

【问题讨论】：

@JsonIdentityInfo。这与 Hibernate 无关，与 JSON 序列化 (Jackson) 无关。

休眠正常工作；但是，这更像是数据库模型到数据库后备存储之上的 OO 模型的错误映射。

看看类似的问题：Jackson serialize problem in @ManyToMany relationship, serialization issue. Only first object of the same entity serializes well, Jackson/Hibernate meta get methods and serialization

【参考方案1】：

由于您的House 有一个ApplicationUser 并且您的ApplicationUser 有一个Houses 的列表，因此您已将这些类定义为循环的。

您的面向对象模型可能与数据库模型 100% 相同。这可能是个坏主意；就像在家庭应用程序的模型中一样，您通常不会将应用程序保存在嵌入应用程序的用户中。

阅读What is “the inverse side of the association” in a bidirectional JPA OneToMany/ManyToOne association?了解更多详情。