Hibernate - Either field A OR B can be null but one of A or B must not be null

Question

Is it possible in hibernate to model a use case in which you have two fields and either of them could be null but at least one of them must not be null? Below is the code I have at the moment but I don't like the fact that I have to set both of them to @Column(nullable = true). In my case I want either the personal email address or the work address. Is there a good way to support this? Or is an alternative approach needed?

public class ApplicantDetails {

    //...

    @OneToOne(optional = false)
    private ContactDetails contactDetails;

    //...
}

public class ContactDetails {

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

    /*Need at least one email address but it doesn't matter which one.*/
    @Column(nullable = true, unique = true)
    private String personalEmail;

    @Column(nullable = true, unique = true)
    private String workEmail;

    //...

}

look at bitwise Xor operations [http://stackoverflow.com/questions/1991380/what-does-the-operator-do-in-java](http://stackoverflow.com/questions/1991380/what-does-the-operator-do-in-java) — levi Clouser, Feb 06 '16 at 21:44

score 1 · Answer 1 · answered Feb 06 '16 at 22:15

I would recommend that you anyway define a CHECK constraint in the database if your database supports some form of it:

CHECK (PERSONAL_EMAIL IS NOT NULL OR WORK_EMAIL IS NOT NULL)

Regarding the middle layer, you can simply write your own validators in services that store/update ContactDetails and raise the corresponding exceptions if attempts to store/update inconsistent state are made, or you can use a validation framework like Hibernate validator.

A quick workaround could also be to utilise entity lifecycle callback methods:

@PrePersist
@PreUpdate
private void validate() {
  if (personalEmail == null && workEmail == null) {
    throw new ValidationException();
  }
}

Hibernate - Either field A OR B can be null but one of A or B must not be null

1 Answers1