I have trouble regarding the insertable of OneToMany.

I'm working with a legacy system which was built on Spring and hibernate4
There is OneToMany/ManyToOne relationship with no one is the "owner"(By defining JoinColumn and insertable/updatable as false on both side).

@Entity
	public static class One{

		@Id
		@GeneratedValue
		public Integer id;

		@OneToMany(
				cascade = {CascadeType.ALL},
				targetEntity = Many.class
		)
		@JoinColumn(name = "one_id", insertable = false, nullable = false, updatable = false)
		public List<Many> manyList;
	}

@Entity
	public static class Many {

		@Id
		@GeneratedValue
		public Integer id;

		@ManyToOne(cascade = {CascadeType.REFRESH},
				targetEntity = One.class
		)
		@JoinColumn(name = "one_id", nullable = false, insertable = false, updatable = false)
		public One one;
	}

although I don't think it's the correct usage, it works fine when try to persist the "Many" by persisting the "One".

But when the legacy system is extracted and imported as a library in a SprintBoot+Hibernate5 application, then the magic above stop working, throwing java.sql.SQLException "Foreignkey doesn't have a default value" exception from MySQL.

The reason is the SQL generated differs between hibernate4/hibernate5.

Hibernate4:

insert 
    into
        JPAUnitTestCase$Many
        (id, one_id) 
    values
        (null, ?)

Hibernate5:

insert 
    into
        JPAUnitTestCase$Many
        (id) 
    values
        (?)

And as per my investigation, the following commit change the behavior on the column insertable initialization.

https://github.com/hibernate/hibernate-orm/commit/c893577efceff237f84d7200e1ef1a2895c95639