Cascade remove with Spring Data JPA (bi-directional) - spring

Question

I've got the following bi-directional relationship between two entity classes:
User
#Entity
#Table(name = "USER")
public class User {
#OneToMany(fetch = FetchType.LAZY, mappedBy = "user")
#Cascade({CascadeType.REMOVE, CascadeType.SAVE_UPDATE})
private Set<Book> books;
}
Book
#Entity
#Table(name = "BOOKS")
public class Book {
#ManyToOne(optional = false)
#JoinColumns({
#JoinColumn(name = "ID", referencedColumnName = "ID"),
#JoinColumn(name = "NAME", referencedColumnName = "NAME"),
})
private User user;
}
I want to remove a User with the delete cascading down to all the books associated with the user. However, when I used a Spring Data CrudRepository:
myDAO.delete(String userId) // interface extending CrudRepository<User, UserPK>
I'm getting:
Caused by: org.hsqldb.HsqlException: integrity constraint violation: foreign key no action; FK_IN88FEHUXOOYQK0YE71USPIEP table: USER
I was trying to use orhpanRemoval, all kind of CascadeTypes both org.hibernate and javax.persistence. I don't want to implement native queries like #Query(Delete from User....) I'm wondering about exception statement foreign key no action whether I directly specified cascade option.

Answer 1

There is a many-to-one relationship from Book to User. Therefore, the Book table requires only a single column to capture the foreign key to the User table.
The code:
#ManyToOne(optional = false)
#JoinColumns({
#JoinColumn(name = "ID", referencedColumnName = "ID"),
#JoinColumn(name = "NAME", referencedColumnName = "NAME"),
})
private User user;
should simply be:
#ManyToOne(optional = false)
#JoinColumn(name = "user_id")
private User user;
When you use the Hibernate Schema Generation Tool (HBM2DDL), foreign key constraints are generated as follows:
ALTER TABLE
BOOK
ADD CONSTRAINT
FK_IN88FEHUXOOYQK0YE71USPIEP
FOREIGN KEY
(USER_ID) REFERENCES USER (ID)
ON UPDATE NO ACTION
ON DELETE NO ACTION;
Notice ON DELETE NO ACTION. This means, when a User instance is deleted, nothing should happen to Book instances associated with it (NO ACTION). This practically means that the User should not be allowed to be deleted.
If you want Book instances associated with a User to be deleted when the User is deleted, the DDL should be:
ALTER TABLE
BOOK
ADD CONSTRAINT
FK_IN88FEHUXOOYQK0YE71USPIEP
FOREIGN KEY
(USER_ID) REFERENCES USER (ID)
ON UPDATE NO ACTION
ON DELETE CASCADE;
This can be generated by adding a Hibernate-specific annotation to the domain model:
class User {
#OneToMany(fetch = FetchType.LAZY, mappedBy = "user")
#Cascade({CascadeType.REMOVE, CascadeType.SAVE_UPDATE})
#OnDelete(OnDeleteAction.CASCADE)
private Set<Book> books;
}