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One-to-One Bidirectional Relationship

One-to-One Bidirectional Relationship

Learn how to make the one-to-one relationship bidirectional and resolve the JSON infinite recursion issue.

We'll cover the following...

Right now, we have a unidirectional one-to-one mapping which means that if we have a Twitter account, we cannot find the name of the player who has that account. A GET request to /profiles only gets the PlayerProfile object and not the Player it is associated with.

It is however possible to find the Twitter account, if we have the Player entity. As can be seen from a GET request to /players, the PlayerProfile entities are also fetched.

GET request to /players and /profiles
GET request to /players and /profiles

In the unidirectional one-to-one relationship, the Player class maintains the relationship. The PlayerProfile class cannot see any change in the relationship.To make this relationship bidirectional, we need to make some modifications to the PlayerProfile class. We will add a field to reference back to the Player class and add the @OneToOne annotation. We will also add getter and setter methods to set the Player value in the PlayerProfile class. This will enable us to fetch the entities in both directions.

Bidirectional relationship
Bidirectional relationship

Bi-directional relationship

To set up a bidirectional relationship, we will add a field of Player class in the PlayerProfile class and add getter and setter methods for the field. This field holds the reference to the associated Player entity.

public class PlayerProfile {

    @Id

    @GeneratedValue(GenertionType.IDENTITY)

    private int id;

    private String twitter;



    private Player player;



    //...



    public Player getPlayer() {

		return player;

	}

	public void setPlayer(Player player) {

		this.player = player;

	}



	@Override

	public String toString() {

		return "PlayerDetail [id=" + id + ", twitter=" + twitter + ", player=" + player + "]";

	} 

}
Adding Player field in PlayerProfile class

The toString() method also needs to be updated to include the newly added player field.

mappedBy attribute

Next, we will add the @OneToOne annotation on the player field. mappedBy is an optional attribute of the @oneToOne annotation which specifies the name of the field which owns the relationship. In our case, it is the playerProfile field in the Player class. The mappedBy ...