Embedded, AttributeOverrides and Transient properties

colebatchd · **Joined:** Wed Nov 26, 2003 4:41 pm **Posts:** 12

Hi all,

I have a class that holds an embedded object, but the embedded object containts a property that is always null for this class, and so I want to override the @Column mapping with a @Transient 'mapping'. As far as I can see this isn't possible and it almost feels like a limitation in the spec.

Obviously with the old way of mapping through config files I can just exclude it from my config. However to do that here I effectively need a new class.

Does anyone have any suggestions for this?

cheers
dim

colebatchd · **Joined:** Wed Nov 26, 2003 4:41 pm **Posts:** 12

Posting here in case someone else finds themselves looking for a workaround. At the moment I'm mapping the property in question as updateable=false, insertable=false and mapping it to a column that does exist. Then using Lifecycle I'm setting the property to null on load so it ends up how I want it. A nasty hack, but it is "working" for now.

I also have the opposite problem (a component with a property mapped as transient that I want to map to a column) and I'm not sure how to handle that either. Any ideas?

cheers
dim

colebatchd · **Joined:** Wed Nov 26, 2003 4:41 pm **Posts:** 12

Hi again,

I assume that I'm writing this to Emmanual, but would be interested in hearing anyone's thoughts.

At the moment it is possible to override column configuration using the @AttributeOverrides annotation. What I'd like to do is make it possible to override a @Transient annotation somehow. I'm thinking something like:

Code:

@Embeddable class Foo
{
  @Transient String firstName;
  @Column String lastName;
}

@Entity class Bar
{
  @Id Long id;
  
  @Embedded
  @TransientOverrides({
    @TransientOverride(name="firstName", transient = false)})
  Foo foo;
}

I haven't fully thought this through, but it seems like a reasonable enough suggestion. I'm looking at PropertyInferredData.execute(boolean) as the method that I'd need to change.

Any advice/suggestions before I dive in and try to make a patch. Obviously @TransientOverrides and @TransientOverride would be hibernate specific annotaions.

cheers
dim

dillenbu · **Joined:** Thu Jun 22, 2006 5:19 pm **Posts:** 8

Dim, I agree that it should be possible to selectively set an embedded class's fields to be transient. I've run into a case where the @Id field of an embedded class interferes with the @Id field of the parent class. I want to both embed a class and reference it as an entity. Here's a test case derived from hibernate-annotations-3.2.0.CR1/test/org/hibernate/test/annotations/TestCase.java that illustrates the problem:

Code:

public class TestHibernateEmbedded extends TestCase {
  
  public TestHibernateEmbedded(String testName) {
    super(testName);
  }
 
  public void testSimpleEmbedding() 
    throws Exception
  {
    Session s = openSession();
    Transaction tx = s.beginTransaction();
    EmbeddableAddress address = new EmbeddableAddress();
    address.setStreetName("Privet Drive");
    address.setStreetNumber("4");
    PersonWithEmbeddedAddress person = new PersonWithEmbeddedAddress();
    person.setAddress(address);
    s.save(person); // should also save embedded addresses
    s.flush();
    tx.commit();
    s.close();  

    s = openSession();
    tx = s.beginTransaction();
    person = (PersonWithEmbeddedAddress )s.get(
      PersonWithEmbeddedAddress.class, person.getId()
    );
    assertNotNull("person should be in database", person);
    assertNotNull("address should be in person", person.getAddress());
    tx.commit();
    s.close();
  }
  
  @Entity
  public static class PersonWithEmbeddedAddress {
    private Long id;
    private EmbeddableAddress address;

    @Id
    @GeneratedValue
    public Long getId() {
      return id;
    }
    public void setId(Long id) {
      this.id = id;
    }
    
    @Embedded
    @AttributeOverrides({
      @AttributeOverride(name="id", column=@Column(name="",insertable=false,updatable=false,columnDefinition=""))
    })
    EmbeddableAddress getAddress() {
      return address;
    }
    public void setAddress(EmbeddableAddress address) {
      this.address = address;
    }
  }
  
  @Embeddable
  public static class EmbeddableAddress {
    private String streetName;
    private String streetNumber;
    private Integer id;
    @Id
    @GeneratedValue
    public Integer getId() {
      return id;
    }
    public void setId(Integer id) {
      this.id = id;
    }
    public String getStreetName() {
      return streetName;
    }
    public void setStreetName(String streetName) {
      this.streetName = streetName;
    }
    public String getStreetNumber() {
      return streetNumber;
    }
    public void setStreetNumber(String streetNumber) {
      this.streetNumber = streetNumber;
    }
  }
  
  public Class[] getMappings() {
    return new Class[]{
      PersonWithEmbeddedAddress.class
    };
  }
}

This test fails with the exception:

Code:

IllegalArgumentException occurred while calling setter of org.sharethedrive.test.hibernate.TestHibernateEmbedded$PersonWithEmbeddedAddress.id
org.hibernate.PropertyAccessException: IllegalArgumentException occurred while calling setter of org.sharethedrive.test.hibernate.TestHibernateEmbedded$PersonWithEmbeddedAddress.id
        at org.hibernate.property.BasicPropertyAccessor$BasicSetter.set(BasicPropertyAccessor.java:104)
        at org.hibernate.tuple.AbstractEntityTuplizer.setIdentifier(AbstractEntityTuplizer.java:204)
        at org.hibernate.persister.entity.AbstractEntityPersister.setIdentifier(AbstractEntityPersister.java:3373)
        at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:53)
        at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:248)
        at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:290)
        at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:180)
        at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:108)
        at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:186)
        at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33)
        at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:175)
        at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27)
        at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:70)
        at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:537)
        at org.hibernate.impl.SessionImpl.save(SessionImpl.java:525)
        at org.hibernate.impl.SessionImpl.save(SessionImpl.java:521)
        at org.sharethedrive.test.hibernate.TestHibernateEmbedded.testSimpleEmbedding(TestHibernateEmbedded.java:31)
        at org.sharethedrive.test.hibernate.HibernateTestCase.runTest(HibernateTestCase.java:74)
Caused by: java.lang.IllegalArgumentException: argument type mismatch
        at org.hibernate.property.BasicPropertyAccessor$BasicSetter.set(BasicPropertyAccessor.java:42)
        ... 32 more

emmanuel · **Posted:** Sun Jul 09, 2006 7:21 am

Hi guys,
I kinda think that such a requirement is sort of nasty.
You somehow break the relationship between the object model and the relational model by changing a logical semantic (@Id, @Transient),a nd I feel uncomfortable about that.
Overriding had always in mind the ability to change a column name, nothing else.

dillenbu · **Joined:** Thu Jun 22, 2006 5:19 pm **Posts:** 8

What do I do if I want to embed a object in some cases and use it stand alone in other cases? To do this, I need to have the id attribute ignored when embedding the object. This is supported easily with .hbm.xml files since I explicitly list the properties I want to persist in each case. With annotations, as they stand now, this is not possible.

emmanuel · **Posted:** Mon Jul 10, 2006 7:17 am

Yes but having the same object threated as both an entity and an embedded object smells like a design flaw. It means a given concept is treated in 2 different ways in your database

dillenbu · **Joined:** Thu Jun 22, 2006 5:19 pm **Posts:** 8

Well, what if, for efficiency reasons, I wanted a Person to embed his home and work addresses since I was going to access those every time I used the Person class, but then I wanted their favorite shopping location as a reference since I only look at it infrequently (say in a special report). Say I keep the person table in its own table space separate from the shopping address table to optimize performance? I could use a join to fetch both person and addresses at the same time, but that's not as fast as direct embedding.

I don't think this should be treated as a design flaw. I think it is a problem to have the annotations of the object model drive the table/database layout. An object-relational mapping tool should do just that, allow one to map their objects to a database layout. If I wanted a object-oriented database, then I could rewind the clock 10 years and use ObjectStore or Versant.

emmanuel · **Posted:** Sun Jul 16, 2006 12:30 pm

For this particular optimization you'll have to fail abck to hbm xml files.

adam_jh · **Joined:** Thu Jul 06, 2006 8:04 am **Posts:** 14

Its an old thread, but still desired for my purposes where I have a MyDate which has a MyTime object. The reason for these objects is that sometimes I want to store dates without a year (eg annual events). Both are marked appropriately with Embeddable and Embedded (they are not meant to be used as separate entities in the db).

Code:

MyDate {
int day
int month
int year
@Embedded
MyTime
}

@Entity
SomeClass {
@Embedded
@TransientOverride(MyTime...)
MyDate

Often MyTime is not needed - is this possible in annotation, or should I create a redundant field in the db of hour and minute?

Thanks