Bidirectional One-To-One Relationship on Foreign Key in Hibernate

In bidirectional association, we will have navigation in both directions, i.e, both side of the association will have the reference to the other side. The both side of the association will implement one of the collection interfaces, if it has the reference to the other entity.

In one to one relationship, one source object can have relationship with only one target object. Let’s consider CD and Artist. So one CD can be written by one Artist or an Artist can write only one CD. So we will create two tables CD and Artist in the database and we will see how one-to-one relationship works step by step.

Now we will apply one-to-one relationship. So only one CD can be written by only one Artist.

In One-To-One relationship on foreign key, CD table has an artistId as foreign key with unique constraint, which is a reference to Artist table.

Step 1. Create tables

Create table – cd

 

Create table – artist

 

Step 2. Create a java project in any Java based IDE and configure for hibernate jars.

Step 3. Create hibernate reverse engineering and configuration file.

 

Step 4. Create hibernate utility class which creates singleton SessionFactory from which Session object will be created.

 

Step 5. Create mapping xml file and POJO for artist table. Look at the xml file, we have <one-to-one /> with property-ref=”artist” which makes sure that one-to-one relationship on foreign key. property-ref declares that the artist property of the Cd class is the inverse of a property on the other side of the association.

 

Step 6. Create mapping xml file and POJO for cd table. cascade represents that if the cascade side of the entity is saved then the other side of the entity will automatically saved by the hibernate.

 

Step 7. Now we will create a main class for testing one-to-one on foreign key.

 

Step 8. Run the main class and see the output as shown below. While we save value for cd, the below values are stored into the database tables.

inserted data into artist table

 

inserted data into cd table

 

Output

 

That’s all. Thanks for your reading.

Soumitra

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