删除与 JPQL 的关系的非所有者也会删除关系答案

【问题标题】：Removing Non-Owner Of relation with JPQL removes relation too删除与 JPQL 的关系的非所有者也会删除关系
【发布时间】：2020-10-02 20:15:07
【问题描述】：

entityManager.remove() VS JPQL DELETE 查询

我知道关系的一侧是所有者，而标记为映射者的另一侧是非所有者。

关系以所有者的持久性保存在数据库中，并在删除时删除。我知道移除非所有者方不会消除关系。 see this link

到目前为止一切顺利。

根据我的经验，使用 JPQL 查询删除非所有者也会删除关系。我不清楚为什么！有没有说服力的解释？

下面的代码 sn-ps 显示了我的概念测试用例：

非所有者

@Entity
public class Book {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    private String title;

    @ManyToMany(mappedBy = "books")
    private Set<Author> authors;
}

所有者：

@Entity
public class Author {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    private String name;

    @ManyToMany
    private Set<Book> books;
}

测试 1

public void persistingRelationOwnerPersistsRelationSuccessfully(){
    Book book = new Book("nonOwner");
    entityManager.persist(book);

    Author author = new Author("owner", new HashSet<>(Arrays.asList(book)));
    entityManager.persist(author);
    entityManager.flush();
}

日志：

Hibernate: insert into book (title, id) values (?, ?)
Hibernate: insert into author (name, id) values (?, ?)
Hibernate: insert into author_books (authors_id, books_id) values (?, ?)

测试 2

public void removingRelationOwnerRemovesRelationSuccessfully(){
    //persist book and author

    entityManager.remove(author);
    entityManager.flush();
}

日志：

Hibernate: insert into book (title, id) values (?, ?)
Hibernate: insert into author (name, id) values (?, ?)
Hibernate: insert into author_books (authors_id, books_id) values (?, ?)
Hibernate: delete from author_books where authors_id=?
Hibernate: delete from author where id=?

测试 3

public void removingNonOwnerWillThrowException(){
    //persist book and author

    entityManager.remove(book);
    entityManager.flush();
}

日志：（如预期）

Hibernate: insert into book (title, id) values (?, ?)
Hibernate: insert into author (name, id) values (?, ?)
Hibernate: insert into author_books (authors_id, books_id) values (?, ?)
Hibernate: delete from book where id=?
javax.persistence.PersistenceException: org.hibernate.exception.ConstraintViolationException: could not execute statement

测试 4

public void removingNonOwnerWithQueryWillRemoveRelation(){
    //persist book and author

    Query query = entityManager.createQuery("delete from Book b where b.title = 'nonOwner'");
    System.out.println("affectedRows = " + query.executeUpdate());
}

日志：（意外行为）

Hibernate: insert into book (title, id) values (?, ?)
Hibernate: insert into author (name, id) values (?, ?)
Hibernate: insert into author_books (authors_id, books_id) values (?, ?)
Hibernate: delete from author_books where (books_id) in (select id from book where title='nonOwner')
Hibernate: delete from book where title='nonOwner'
affectedRows = 1

【问题讨论】：

标签： java hibernate jpa jpql

【解决方案1】：

这可能是一个错误，因为这应该取决于 Book#authors 关联的级联设置，删除 DML 语句可能会忽略该设置。您应该使用复制者 https://hibernate.atlassian.net/

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