Question

Documenting this here because I just wasted an hour trying to figure this out.

I have an entity Foo with:

@ManyToOne(optional = false)
@JoinColumn(name = "barId")
private Bar bar;

Why does Hibernate not create a foreign key constraint on foo.bar -> bar.id ?

Answer 1

It’s because MySQL does not support foreign key constraints on tables created with ENGINE=MyISAM. You need to create (both!) tables with ENGINE=InnoDB. You can do so by tweaking my.cnf, and adding a default, or by using a special variable in your JDBC URL:

jdbc:mysql://localhost/dbname?characterEncoding=utf8&sessionVariables=storage_engine=InnoDB