Question

I have a domain object that contains another domain object; call them A and B. B contains a blob (an image file) which can be large. As long as I am only dealing with one A at a time having B on A isn’t a concern. However, sometimes I’ll be dealing with thousands of A in which carrying around the blob on B causes heap to run out. When I am dealing with so many A I really don’t need B anyway.

Is there some way of telling Hibernate to ignore this property for a particular call? Should I just make B transient and deal with updating/deleting manually in this case?

Right now to get around this problem I use a SQL query to pull all the ids I want then iterate over that list getting each domain object out, doing what I need, then evicting it.

Also, I can’t lazy load B because I’m in a servlet environment so my Hibernate session is closed before I access the properties in most cases.

@Entity
@Table(name="A")
public class A {

  private Long id

  @OneToOne(fetch = FetchType.EAGER, cascade = { CascadeType.ALL }, orphanRemoval = true)
  @JoinColumn(name = "a_id", referencedColumnName = "b_id", nullable = true)
  @NotFound(action = NotFoundAction.IGNORE)
  private B b

  ...getters and setters
}

@Entity
@Table(name="B")
public class B {
  private Long id;
  private byte[] blob;

  ...getters and setters
}

Thanks

Answer 1

Is there some way of telling Hibernate to ignore this property for a particular call? Should I just make B transient and deal with updating/deleting manually in this case?

One option would be to use lazy property fetching (this requires bytecode instrumentation, refer to the documentation). So you could map B like this:

@Entity
@Table(name="B")
public class B {
  @Id
  private Long id;

  @Basic(fetch = FetchType.LAZY)
  @Lob
  private byte[] blob;

  // getters and setters
}

And, as documented:

You can force the usual eager fetching of properties using fetch all properties in HQL.

Another option would be to use an alternative version of A (A’) without the B, for this special use case.

References

• Hibernate Annotations Reference Guide
  • 2.2.2. Mapping simple properties
• Hibernate Core Reference Guide
  • 20.1.8. Using lazy property fetching