Question

I am having trouble with this query but ONLY under HSQLDB. We use Oracle for production database and HSQL for automated integration tests. Here’s my main object:

@Entity
@Table(name="STUDENTS")
@org.hibernate.annotations.Proxy(lazy=false)
public class Student implements Serializable {
...
   @OneToMany(fetch=FetchType.LAZY)
   @JoinColumn(name="STUDENTID",referencedColumnName="ID")
   private Set<StudentRace> races;
...
}

StudentRace looks like this:

@Entity
@Table(name="STUDENTRACE")
@org.hibernate.annotations.Proxy(lazy=false)
public class StudentRace implements Serializable {
...
    @Column(name="STUDENTID")
    private Integer studentid;
...
}

And my JPA query is like this:

entityManager.createQuery("select distinct s from Student s left join fetch s.races "+
  "where s.schoolNumber = :schoolNumber");

I know I have correct data in the HSQLDB database – I can manually do a query and see the data. Yet the Student objects always have “races” as null. As I said, this query works fine in Oracle. Is there some kind of HSQLDB setup thing I’m missing?

Edit: Like this? In Student:

@OneToMany(fetch=FetchType.LAZY, mappedBy="id")
private Set<StudentRace> races;

In StudentRace:

@ManyToOne
@JoinColumn(name="STUDENTID")
private Student student;

Still no luck. The “races” element is still null.

Answer 1

Your mapping is incorrect, because the STUDENTRACE.STUDENTID column is mapped twice: once as a JoinColumn in Student, and once as a column in StudentRace.

Either make the association unidirectional and remove the studentid field in StudentRace, or make it bidirectional, and have a Student student field in StudentRace, mapped as a ManyToOne, as shown in this example from the Hibernate documentation.