Hibernate doesn't generate cascade

问题

I have a set hibernate.hbm2ddl.auto to create so that Hibernate creates the tables in mysql for me.

However, it doesn't seem that hibernate correctly adds Cascade on the references in the table. It does however work when I for instance delete a row, and I have a delete cascade as hibernate annotation. So I guess that means that Hibernate reads the annoation on runtime, and perform cascading manually?

Is that normal behavior?

For instance:

@Entity
class Report {
    @OneToOne(cascade = CascadeType.ALL)
    public File getPdf() {
    return pdf;
}
}

Here I have set cascade to ALL. However, when running show create table Report

Report | CREATE TABLE `Report` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `pdf_id` bigint(20) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `FK91B14154FDE6543A` (`pdf_id`),
  CONSTRAINT `FK91B14154FDE6543A` FOREIGN KEY (`pdf_id`) REFERENCES `File` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |

It doesn't say anything about cascading other then the foreign key. In my opinion, it should have added the ON DELETE CASCADE ON DELETE UPDATE

回答1:

The CascadeType and @Cascade definitions are not translated into DDL, they tell Hibernate how to behave when an operation is performed.

However, there is @OnDelete that you can use on the parent to get the foreign key created with the appropriate on delete cascade clause.

来源：https://stackoverflow.com/questions/2856460/hibernate-doesnt-generate-cascade