CODEWITHSUNDEEP
javajpa
UcanDoIt
UcanDoIt

Reputation: 1845

how to have the correct cardinality of the relationship?

I've created a project with maven on netbeans. after defining the tables in mySql program i'm trying to generate the entity classes from database, using the Netbeans IDE.

The thing is that I have a table Cage and a table Animal and i wnat it to be a one to one relationship, but when i generate the entities the IDE put it as a one to many relationship (with the anotattions).

I think that my tables, in the database, are well created What am i doing wrong? How can i fix this problem?

Upvotes: 0

Views: 558

Answers (1)

geoand
geoand

Reputation: 64039

There are three cases where a @OneToOne would be used by a DB schema reverse engineering tool:

  1. The associated entities share the same primary keys values

  2. A foreign key is held by one of the entities and this FK column in the database has a unique constraint in order to emulate one-to-one multiplicity

  3. An association table is used to store the link between the 2 entities (a unique constraint has to be defined on each FK to ensure the one to one multiplicity).

If your tables do not have one of the aforementioned characteristics @OneToMany will be used.

Check out this tutorial for more details (that is where the three aforementioned cases are from)

Upvotes: 1

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