Hibernate: how to create a constraint with two columns (field) of the same table (or entity)

Question

I have an hibernate entity which contains two dates: start and finish.

@Entity
public class MyEntity{ 

    private Date start
    private Date finish;
    ...
    @Temporal(TemporalType.DATE)
    @Column(name = "start", nullable = false)
    public Date getStart() {
        return start
    }

    @Temporal(TemporalType.DATE)
    @Column(name = "finish", nullable = false)
    public Date getFinish() {
        return finish;
    }
}

I would like to introduce a constraint that says start must be before finish,
can I do this kind of validation/check in the hibernate entities in order to avoid to write invalid data in my table?
If yes, how?
My guess is not, probably I have to write a trigger.. is it right? any better ideas?

Maksym Demidas · Accepted Answer · 2013-04-11 16:29:55Z

2

You can use Hibernate Validator to add vlaidation for your entities. You need to introduce your own custom constraint.

Or you can do it manually in your DAO layer:

public class MyEntityDAO{ 

    ....

    protected void save(MyEntity entity) {
      // check dates
      // throw some exception in a case of problems
      getCurrentSession().saveOrUpdate(entity);
    }
}

As a downside this will not work if you save some parent entity and MyEntity entity will be saved by cascade.

An easier to do solution may be using @PrePersist:

@Entity
public class MyEntity{ 

    ....

    @PrePersist
    protected void checkDates() {
      // check dates
      // throw some runtime exception in a case of problems
    }
}

But I am not sure that in this case trnsaction will be rolled back by default.

edited Apr 11, 2013 at 16:29

answered Apr 11, 2013 at 16:05

Maksym Demidas

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Comments

bornleo · Accepted Answer · 2013-04-11 17:57:54Z

1

+1 to Maksym for @PrePersist suggestion, just taking the idea further.

You can also use @PrePersist with @EntityListeners to handle the entity validations:

public class MyEntityValidationEventListener {
   @PrePersist
   public void validate(Object entity) {....}
}

@Entity
@EntityListeners(MyEntityValidationEventListener.class)
public class MyEntity {...}

answered Apr 11, 2013 at 17:57

bornleo

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1 Comment

Maksym Demidas Over a year ago

+1 thnaks for sharing. It will give you ability to separate your entity (POJO) and validation code

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