CODEWITHSUNDEEP
javahibernatejpa
Abdul Rauf
Abdul Rauf

Reputation: 756

OneToOne relationship, keep only foreign key

I am trying to establish a OneToOne relationship between two entities (PartnerDetails and JWTData. How ever, I only want to store the primary key of PartnerDetails entity in JWTData, not the whole object, like this.

@Entity
@Data
@Table(name = "partner_details")
public class PartnerDetails {

  @Id
  @Column(name = "partner_id")
  private String partnerId;

  @OneToOne(cascade = CascadeType.ALL, mappedBy = "partnerId")
  private JWTData jwtData;

}

@Entity
@Data
@Table(name = "jwt_data")
@NoArgsConstructor
public class JWTData {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;

  @OneToOne(targetEntity = PartnerDetails.class)
  @JoinColumn(name = "partner_id", foreignKey = @ForeignKey(name = "fk_jwt_partnerdetails_partnerid"))
  private String partnerId;

  @NotBlank
  private String secret;
}

But after fetching the JWTData using repository, Hibernate cannot convert the String to a PartnerDetails. Can this be done using any other way?

Upvotes: 0

Views: 364

Answers (1)

K.Nicholas
K.Nicholas

Reputation: 11561

If you just add PartnerDetails to JWTData then JPA will know to use only the id. JPA is an Object Oriented framework so you should reference objects unless you specifically want a field. JPA handles the details for you. Note that in this configuration JWTData in the "owning" entity because of the mappedBy annotation, therefore only setting the partnerDetails field in a JWTData instance will persist the relationship to the database. The jwtData field in PartnerDetails is for query results only and makes for a Bidirectional instead of a Unidirectional mapping. Also, because of this, having a CascadeType setting generally only makes sense on the owning entity since it is the one handling the database updates and deletes.

When playing around with JPA be sure to turn on the SQL output so that you know what is actually happening.

@Entity
@Data
@Table(name = "partner_details")
public class PartnerDetails {

  @Id
  @Column(name = "partner_id")
  private String partnerId;

  @OneToOne(mappedBy = "partnerDetails")
  private JWTData jwtData;


@Entity
@Data
@Table(name = "jwt_data")
@NoArgsConstructor
public class JWTData {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;

  // even though it looks like the entire class it's only saving the id to the database.
  @OneToOne
  private PartnerDetails partnerDetails;

Upvotes: 1

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