Single Inheritance / ConstraintViolationException / Postgre

[toni]

Hi,

using a single table inheritance strategy with postgres 7.3 always causes a ConstraintViolationException when I try to merge the changes.

I first create a new enity bean, which works. Then I add it to a OneToMany collection of another entity bean and try to merge the change. This is when I get a ConstraintViolationException.

Here is the setup:

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)

public class Person implements Serializable
{
 @Id
 @GeneratedValue(strategy = GenerationType.IDENTITY)
 long id;
..
}

@Entity
@Name("junior")

public class Junior extends Person
{
...
}

@Entity
@Name("school")

public class School implements Serializable
{
 @Id
 @NotNull
 @Length(min = 5, max = 40)
 String schoolName

 @OneToMany(cascade = {CascadeType.ALL})
 List<Juniors> juniors = new ArrayList<Juniors>();

 @OneToMany(cascade = {CascadeType.ALL})
 List<Softmore> softmores = new ArrayList<Softmore>();

 @OneToMany(cascade = {CascadeType.ALL})
 List<Senior> seniors = new ArrayList<Senior>();
...

The following code always throws a ConstraintViolationException

 // works
 entityManager.persist(junior);
 // this causes a contraint violation
 school.getJuniors().add(junior);
 school = entityManager.merge(rewriteConfiguration);

The reason why this happens, is because the columns of the database table, which keeps track of the OneToMany relationships are all defined to be NOT NULL. Here comes the table:

school_schoolname character varying(40)
NOT NULL

juniors_id bigint
NOT NULL

softmores_id bigint
NOT NULL

seniors_id bigint
NOT NULL

However, all those columns SHOULD be nullable, but hibernate does not set them up like this. How can I make sure hibernate does this?

[waynebaylor]

you could try @Column(nullable=false)

[toni]

Thanks for the advice. However, the problem is that those columns are out of scope for any annotations I place on my columns.

That's because those columns are automatically generated by hibernate to keep track of the OneToMany relationships. In other words I have no column on which I could place this annotation - because I don't define them (Only indirectly versus the OneToMany annotation).

Hibernate should realize byitself that only ONE of those columns should be set per row and that the other columns should be set to NULL.

Any other ideas?

[waynebaylor]

you can use @Column like this:

@OneToMany(cascade = {CascadeType.ALL})
@Column(nullable=false)
List<Juniors> juniors = new ArrayList<Juniors>();