Spring Data REST javax.persistence.RollbackException：提交事务时出错

Question

我有两个实体：

@Data
@Entity(name = "users")
@NoArgsConstructor
@RequiredArgsConstructor
@EqualsAndHashCode
public User {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name="id", unique = true, nullable = false)
    private Integer userId;

    private String userName;

    @OneToMany(fetch = FetchType.EAGER, cascade = {CascadeType.PERSIST, CascadeType.REMOVE})
    @JoinColumn(name = "user_id")
    @Fetch(value = FetchMode.SUBSELECT)
    private List<Degree> degreeList;

}

和

@Data
@Entity(name = "degrees")
@NoArgsConstructor
@RequiredArgsConstructor
@EqualsAndHashCode
public Degree {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name="id", unique = true, nullable = false)
    private Integer degreeId;

    private String degreeTitle;
}

RestResources 是：

@RepositoryRestResource(collectionResourceRel = "users", path = "users")
public interface UserRestRepository extends CrudRepository<User, Integer> {
}

然后：

@RepositoryRestResource(collectionResourceRel = "degrees", path = "degrees")
public interface DegreeRestRepository extends CrudRepository<Degree, Integer> {
}

我必须使用 https://www.myhost.com/api/users/{userId}/degreeList 端点在 foo 的 barList 中添加新的 bar，如图所示：

但我得到了：

{
    "timestamp": "2020-04-17T05:16:51.520+0000",
    "status": 500,
    "error": "Internal Server Error",
    "message": "Could not commit JPA transaction; nested exception is javax.persistence.RollbackException: Error while committing the transaction",
    "path": "/api/users/4/degreeList"
}

我搜了一下，发现必须先保存Degree再更新degreeList，请问该怎么做呢

Answer 1

Spring Data REST 是基于 URI 的（遵循 HATEOAS 规则）。如果要将“degree”添加到“degreeList”中，确实首先需要创建degree：

HTTP POST 到https://www.myhost.com/api/degrees

请求正文必须是内容类型application/json

之后，您会在响应中取回学位 ID。您使用此 ID 将度数添加到列表中：

HTTP POST 到https://www.myhost.com/api/users/{userId}/degreeList

重要：这次请求的内容类型是text/uri-list！正文必须是纯文本，并且应该只包含 URI

https://www.myhost.com/api/degrees/{degreeId}