Question

我有两个表，“书籍”和“书店”都有@OneToMany对“book_to_bookstore”表的引用，该表记录了书店中有多少本书。如果书籍或书店被删除，那么这些信息也应该消失。

因此我使用标准JPA CascadeType.ALL和orphanRemoval = true。为了使“正确”的SQL模式在使用Java时访问它时也能正常工作，我添加了EclipseLink特定的@CascadeOnDelete注释，期望在两个FOREIGN KEY语句之后出现CASCADE ON DELETE。

有趣的是，它只出现在其中一个我无法解释之后！

我尝试了MySQL和PostgreSQL的DDL生成，但两者都是一样的。

为什么？

可编译的迷你项目在这里： SVN + SSH：//lathspell@svn.code.sf.net/p/lathspellsphp/code/java_test_eclipselink_cascade_bug

重要的课程：

public class Bookstore implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "id")

    private Integer id;
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "bookstoreId", orphanRemoval = true)
    @CascadeOnDelete
    private List<BookToBookstore> bookToBookstoreList;
    ...

public class Book implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "id")
    private Integer id;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "bookId", orphanRemoval = true)
    @CascadeOnDelete
    private List<BookToBookstore> bookToBookstoreList;
    ...

public class BookToBookstore implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "id")
    private Integer id;

    @JoinColumn(name = "bookstore_id", referencedColumnName = "id")
    @ManyToOne(optional = false)
    private Bookstore bookstoreId;

    @JoinColumn(name = "book_id", referencedColumnName = "id")
    @ManyToOne(optional = false)
    private Book bookId;
    ...

为MySQL生成的SQL，请注意 last 行中缺少的CASCADE ON DELETE：

CREATE TABLE books (id INTEGER AUTO_INCREMENT NOT NULL, PRIMARY KEY (id))
CREATE TABLE book_to_bookstore (id INTEGER AUTO_INCREMENT NOT NULL, book_id INTEGER, bookstore_id INTEGER, PRIMARY KEY (id))
CREATE TABLE bookstores (id INTEGER AUTO_INCREMENT NOT NULL, PRIMARY KEY (id))
ALTER TABLE book_to_bookstore ADD CONSTRAINT FK_book_to_bookstore_book_id FOREIGN KEY (book_id) REFERENCES books (id) ON DELETE CASCADE
ALTER TABLE book_to_bookstore ADD CONSTRAINT FK_book_to_bookstore_bookstore_id FOREIGN KEY (bookstore_id) REFERENCES bookstores (id)

EclipseLink @CascadeOnDelete有时只能工作吗？

0 个答案: