CODEWITHSUNDEEP
javahibernatejpa
Whimusical
Whimusical

Reputation: 6649

@OneToMany by means of mappedBy without @JoinColumns

I am founding some legacy code in my job where some of the following shows up:

For simplification, imagine a One class and a Many class. In One Class I got:

 @OneToMany(mappedBy = "toOne")
 private List<Many> manies;

But in Many class, the field toOne is defined as:

@JoinColumn(name = "unrelated", referencedColumnName = "id") 
UnrelatedEntity toOne;

The only plausible explanation is that toOne field has both a relation with Unrelated and also a FK to Many. But, is it possible to have a @OneToMany using mappedBy without the use of a local or remote @JoinColumn? I did not see any example using that simplification. Is it using One.@Id for the join automagically?

Upvotes: 0

Views: 639

Answers (1)

Neil Stockton
Neil Stockton

Reputation: 11531

"mappedBy" links the 2 sides of the relation nothing more. If you omit the JoinColumn then it will use a join table to manage the relation. If you use JoinColumn then it manages the relation via an FK in the "many side". Very simple. It will use how many @Id fields there are in the "1 side" for the FK.

Upvotes: 2

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