JPA CascadeType Persist不适用于spring数据 [英] JPA CascadeType Persist doesn't work with spring data

问题描述

我有两个实体，用户:

@Data
@EqualsAndHashCode(exclude = "id")
@Entity
@Table(name = "users")
public class User {

    @Id
    @SequenceGenerator(name = "user_id_seq_gen", sequenceName = "users_id_seq", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "user_id_seq_gen")
    private long id;
    @Column(nullable = false, unique = true, length = 100)
    @NotNull
    @Length(min = 4, max = 100)
    private String email;
    @Column(nullable = false, length = 50)
    @NotNull
    @Length(min = 6, max = 100)
    private String password;

}

和验证:

@Data
@AllArgsConstructor
@NoArgsConstructor
@Entity
public class Verification {

    @Id
    @Column(length = 20)
    private String code;

    @OneToOne(cascade = {CascadeType.PERSIST})
    private User user;

}

然后我用这种方法保存这些实体:

And I save these entities in this method:

@Transactional
    public void registerUser(User user) {
        user.setPassword(DigestUtils.md5Hex(user.getPassword()));
        String code = RandomStringUtils.random(20, true, true);
        Verification verification;
        while(true) {
            if (!verificationRepository.existsByCode(code)) {
                verification = new Verification(code, user);
                break;
            } else {
                code = RandomStringUtils.random(20, true, true);
            }
        }
        verificationRepository.save(verification);
    }

但是CascadeType持久不起作用，它引发以下异常:

But CascadeType persist doesn't work, it throws the following exception:

org.postgresql.util.PSQLException: ERROR: null value in column "user_id" violates not-null constraint
  Подробности: Failing row contains (Oda2AolKrQXYSxuVmclO, null).

但是当我将层叠类型更改为MERGE时，它可以工作.而且我不明白为什么，因为我同时创建了新用户和新验证.首先，我需要保存用户，然后进行验证.你知道答案吗?

But when I change cascade type to MERGE, it works. And I don't understand why, because I create new User and new Verification at the same time. And first I need to save the user, then the verification. Do you know the answer?

推荐答案

Spring Data JPA使用ID来确定实例是否为新实例.既然您似乎将id设置为非空值，那么Spring Data JPA会将其视为现有实体，并调用merge而不是persist.

Spring Data JPA uses the ID to determine if the instance is new or not. Since it seems you are setting the id to a non-null value Spring Data JPA considers it an existing entity and calls merge instead of persist.

阅读参考文档中的保存实体" 有关如何调整该行为.

Read "Saving Entities" in the Reference Documentation about how to tweak that behavior.

我建议从域驱动设计和聚合/聚合根的角度进行思考，以便确定应通过Cascade.ALL + DELETE_ORPHAN链接的实体以及那些没有任何级联和独立存储库的实体.

I recommend thinking in terms of Domain Driven Design and Aggregates/Aggregate Roots in order to determine the entities which should be linked via Cascade.ALL + DELETE_ORPHAN and those without any cascading and separate repositories instead.

我建议阅读有关该主题的"推进企业DDD ".

I recommend reading "Advancing Enterprise DDD" about the topic.

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