Specifying a primary key on @ElementCollection

问题

So, there is that behavior with innodb that can cause problem if some tables lack of primary key.

So with Hibernate, I am looking for a key to specifies a primary key on a @ElementCollection table with a Set as the underling data structure.

I found a way to have a primary key with a map, but it is kind of weird because I do not need a map.

I also found an answer related to @Embeddable, but I do not need that kind of complexities. I am using a Set or Set as the data structure in my entities.

Any idea how to achieve that?

回答1:

If you use a Set and make the element Column be not null, then hibernate will make a primary key with the join column and element column.

Example:

@Column(name = "STRINGS", nullable = false)
@ElementCollection
private Set<String> strings;

回答2:

@ElementCollection cannot take a primary key, because an Embeddable types cannot have an identifier.

You can add an @OrderColumn to optimize the generates SQL statements.

If you need a primary key, then you should turn the @ElementCollection into a @OneToMany association.

来源：https://stackoverflow.com/questions/30053647/specifying-a-primary-key-on-elementcollection