How does the JPA handle partial, disjoint inheritance (using InheritanceType.JOINED in a class script at the table) along with EntityManager.find ()?

Question

I have a problem modeling / understanding partial , disjoint inheritance with JPA annotations.

Here are four tables:

CREATE TABLE Persons (
  id INTEGER NOT NULL,
  first_name VARCHAR(50) NOT NULL,
  last_name VARCHAR(50) NOT NULL,
  PRIMARY KEY (id));

CREATE TABLE Referees (
  id INTEGER NOT NULL,
  license_nbr VARCHAR(10) DEFAULT NULL NULL,
  PRIMARY KEY (id),
  CONSTRAINT referees_persons_fk
    FOREIGN KEY (id)
    REFERENCES Persons (id)
    ON DELETE CASCADE
    ON UPDATE CASCADE);

CREATE TABLE Coaches (
  id INTEGER NOT NULL,
  license_nbr VARCHAR(10) DEFAULT NULL NULL,
  PRIMARY KEY (id),
  CONSTRAINT coaches_persons_fk
    FOREIGN KEY (id)
    REFERENCES Persons (id)
    ON DELETE CASCADE
    ON UPDATE CASCADE);

CREATE TABLE Players (
  id INTEGER NOT NULL,
  registration_nbr VARCHAR(20) DEFAULT NULL NULL,
  PRIMARY KEY (id),
  CONSTRAINT players_persons_fk
    FOREIGN KEY (id)
    REFERENCES Persons (id)
    ON DELETE CASCADE
    ON UPDATE CASCADE);

My abbreviated entity classes:

@Entity
@Table(name = "Persons")
@Inheritance(strategy = InheritanceType.JOINED)
public class Person implements Serializable
{
    @Id
    @Column(name = "id")
    private Integer id;

    @Column(name = "first_name")
    private String firstName;

    @Column(name = "last_name")
    private String lastName;

    ...
}

@Entity
@Table(name = "Referees")
public class Referee extends Person implements Serializable
{
    @Column(name = "license_nbr")
    private String licenseNbr = null;

    ...
}

@Entity
@Table(name = "Coaches")
public class Coach extends Person implements Serializable
{
    @Column(name = "license_nbr")
    private String licenseNbr = null;

    ...
}

@Entity
@Table(name = "Players")
public class Player extends Person implements Serializable
{
    @Column(name = "registration_nbr")
    private String registrationNbr = null;

    ...
}

Partial Inheritance: Individuals may exist without appropriate referees, coaches or players

Disjoint inheritance: there can be any number of relevant entities, that is, a person can simultaneously be a judge, coach and player, possibly any combination of the three. Each subcategory can have only one or one object, but not several.

, , Person . , Person/s , .

Java ORM? ?

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// Michael Jordan: the person who only a player, too

// EclipseLink 2.1.1 ( 1): ?
// EclipseLink 2.2.0 ( 1): ?
// Hibernate 3.6     (-1): wrong Player instance
Person pe1 = em.find(Person.class, 1);
System.out.println("Loaded person = " + pe1);

// EclipseLink 2.1.1 ( 1): ?
// EclipseLink 2.2.0 ( 1): ?
// Hibernate 3.6     (+1): correct Player instance
Player pl1 = em.find(Player.class, 1);
System.out.println("Loaded player = " + pl1);

// EclipseLink 2.1.1 ( 1): ?
// EclipseLink 2.2.0 ( 1): ?
// Hibernate 3.6     (+1): correct null
Referee re1 = em.find(Referee.class, 1);
System.out.println("Loaded referee = " + re1);

// EclipseLink 2.1.1 ( 1): ?
// EclipseLink 2.2.0 ( 1): ?
// Hibernate 3.6     (+1): correct null
Coach ch1 = em.find(Coach.class, 1);
System.out.println("Loaded coach = " + ch1);

System.out.println();
System.out.println();

// Dirk Nowitzki: the person who also a player *and* a referee

// EclipseLink 2.1.1 ( 1): ?
// EclipseLink 2.2.0 ( 1): ?
// Hibernate 3.6     (-1): wrong Player instance
Person pe2 = em.find(Person.class, 2);
System.out.println("Loaded person = " + pe2);

// EclipseLink 2.1.1 ( 1): ?
// EclipseLink 2.2.0 ( 1): ?
// Hibernate 3.6     (+1): correct Player instance
Player pl2 = em.find(Player.class, 2);
System.out.println("Loaded player = " + pl2);

// EclipseLink 2.1.1 ( 1): ?
// EclipseLink 2.2.0 ( 1): ?
// Hibernate 3.6     (-1): wrong null
Referee re2 = em.find(Referee.class, 2);
System.out.println("Loaded referee = " + re2);

// EclipseLink 2.1.1 ( 1): ?
// EclipseLink 2.2.0 ( 1): ?
// Hibernate 3.6     (+1): correct null
Coach ch2 = em.find(Coach.class, 2);
System.out.println("Loaded coach = " + ch2);

System.out.println();
System.out.println();

// Blake Griffin: the person who also a player, referee, *and* coach

// EclipseLink 2.1.1 ( 1): ?
// EclipseLink 2.2.0 ( 1): ?
// Hibernate 3.6     (-1): wrong Player instance
Person pe3 = em.find(Person.class, 3);
System.out.println("Loaded person = " + pe3);

// EclipseLink 2.1.1 ( 1): ?
// EclipseLink 2.2.0 ( 1): ?
// Hibernate 3.6     (+1): correct Player instance
Player pl3 = em.find(Player.class, 3);
System.out.println("Loaded player = " + pl3);

// EclipseLink 2.1.1 ( 1): ?
// EclipseLink 2.2.0 ( 1): ?
// Hibernate 3.6     (-1): wrong null
Referee re3 = em.find(Referee.class, 3);
System.out.println("Loaded referee = " + re3);

// EclipseLink 2.1.1 ( 1): ?
// EclipseLink 2.2.0 ( 1): ?
// Hibernate 3.6     (-1): wrong null
Coach ch3 = em.find(Coach.class, 3);
System.out.println("Loaded coach = " + ch3);

EclipseLink 2.1.1 2.2.0 EntityManager.find(...), Hibernate, , . " " . , ORM JPA, .

, Hibernate Player, Coach Referee, Player.

JavaSE/HSQLDB/Hibernate : http://www.kawoolutions.com/media/persons-partial-nondisjoint-inheritance.zip

, JPA ? ( !)?

Answer 1

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  project0_.name as name66_,
  project0_1_.budget as budget67_,
  case 
   when project0_1_.id is not null then 1 
   when project0_2_.id is not null then 2 
   when project0_.id is not null then 0 
   else -1 
  end as clazz_ 
 from
  Project project0_ 
 left outer join
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   on project0_.id=project0_1_.id 
 left outer join
  SMALLPROJECT project0_2_ 
   on project0_.id=project0_2_.id

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Answer 2

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