Which annotation is used to define a one-to-one relationship in JPA?

Java MCQ: Which annotation is used to define a one-to-one relationship in JPA?

Answer:

Explanation:

The @OneToOne annotation is used to define a one-to-one relationship in JPA. This type of relationship indicates that one instance of an entity is associated with exactly one instance of another entity. The @OneToOne annotation is used on both sides of the relationship, with one side typically owning the relationship (using @JoinColumn) and the other side mapped to it.

Here’s an example:

@Entity
public class Employee {
    @Id
    private Long id;

    @OneToOne
    @JoinColumn(name = "address_id")
    private Address address;

    private String name;

    // Getters and setters
}

In this example, the Employee entity has a one-to-one relationship with the Address entity, meaning that each employee has a unique address. The @JoinColumn annotation specifies the foreign key column that references the Address entity.

One-to-one relationships are used in cases where each entity has a unique counterpart, and they are easily represented in JPA using the @OneToOne annotation.

Reference links:

https://www.rameshfadatare.com/learn-java-programming/
https://www.javaguides.net/p/java-tutorial-learn-java-programming.html