Mapping subclass list in Java using hibernate annotations

Question

I have a problem with mapping a list of subclasses:
Model situation - I have an abstract class:

@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(
        name="shapeType",
        discriminatorType=DiscriminatorType.STRING
    )
public abstract class Shape{
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    protected Long id;

    @Column(name="owner_id")
    private Long ownerId;

    @ManyToOne
    @JoinColumn(updatable=false, insertable=false, name="owner_id")
    private Owner owner;
}

and its subclasses:

@Entity
@DiscriminatorValue(value="triangel")
public class Triangel extends Shape {
}

and:

@Entity
@DiscriminatorValue(value="circle")
public class Circle extends Shape {
}

Then, I have a class Owner, which has a list of subclasses:

@Entity
public class Owner {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long id;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "owner", targetEntity=Shape.class)
    private List<Triangel> triangels;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "owner", targetEntity=Shape.class)
    private List<Circle> circles;
}

When I loop over the triangel list:

for(Object triangel: owner.getTriangels()){ //Using Triangel as a type throws ClassCastException
    logger.info(triangel.toString());
}

it iterates all shapes objects, not just triangel objects. It seems to me, that hibernate ignores DiscriminatorColumn during the selection subclasses in that situation.

Mind, that without specification targetEntity as Shape.class in @OneToMany, my application did not even start and had some problem with mapping initialization.

Configuration from pom.xml:

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.34</version>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-core</artifactId>
    <version>4.3.7.Final</version>
</dependency>
<dependency>
    <groupId>org.hibernate.javax.persistence</groupId>
    <artifactId>hibernate-jpa-2.1-api</artifactId>
    <version>1.0.0.Final</version>
</dependency>
 <dependency>
    <groupId>org.eclipse.persistence</groupId>
    <artifactId>javax.persistence</artifactId>
    <version>2.1.0</version>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>commons-dbcp</groupId>
    <artifactId>commons-dbcp</artifactId>
    <version>1.2.2</version>
    <scope>provided</scope>
</dependency>

How am I supposed to do correct mapping configuration of that design?

what happens when you change the target entity to Triangle.class? and for circle Circle.class — Bilbo Baggins, Dec 24 '15 at 05:55
"owner.triangels" should only return objects that are of the type Triangel. That is the only thing that Java should permit, and the only thing that the JPA implementation I use will do (DataNucleus). I fail to see why targetEntity is even needed since the generics specification is visible to the JPA implementation. That said, it makes little sense to reuse "owner" for the other end of "circles" — Neil Stockton, Dec 28 '15 at 14:22

score 0 · Answer 1 · answered Mar 12 '17 at 20:33

0

That's something that got recently fixed in Hibernate 5.2.7: https://hibernate.atlassian.net/browse/HHH-11375

answered Mar 12 '17 at 20:33

Christian Beikov

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Mapping subclass list in Java using hibernate annotations

1 Answers1