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jpaentitysubclasssuperclasscomposite-primary-key

Try to use EmbeddedId in Superclass

I have the following problem:

I have a base class (used as superclass) with a composite primary key. And now I'am trying to setup subclasses correctly from the base class, but this doesn't work! Could somebody help me? Thanks

Here are my classes:

BasePK.java

@Embeddable
public class BasePK implements Serializeable {
  protected String base1;
  protected Timestamp base2;
  ..
}

Base.java

@MappedSuperclass
@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
public abstract class Base implements Serializeable {
  @EmbeddedId
  protected BasePK id;
  ..
}

SubClassA.java

@Entity
public class SubClassA extends Base implements Serializeable {

  @OneToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER, mappedBy="attrA")
  protected List<SubClassB> attrsB;

  protected String attrA1;
  protected String attrA2;
  ..
}

SubClassB.java

@Entity
public class SubClassB extends Base implements Serializeable {

  @ManyToOne(fetch=FetchType.LAZY)
  private SubClassA attrA;

  protected String attrB1;
  protected String attrB2;
  ..
}

SubClassC.java

@Entity
public class SubClassC extends SubClassA implements Serializeable {


  protected String attrC1;
  protected String attrC2;
  ..
}

When I try to run the project, the following excetions are made:

[EL Info]: 2012-11-01 23:31:18.739--ServerSession(2063330336)--EclipseLink, version: Eclipse Persistence Services - 2.4.1.v20121003-ad44345
[EL Warning]: metadata: 2012-11-01 23:31:19.199--ServerSession(2063330336)--Reverting the lazy setting on the OneToOne or ManyToOne attribute [controlledObject] for the entity class [class logyourlife.entities.ChangeRecord] since weaving was not enabled or did not occur.
[EL Severe]: 2012-11-01 23:31:19.229--ServerSession(2063330336)--Exception [EclipseLink-0] (Eclipse Persistence Services - 2.4.1.v20121003-ad44345): org.eclipse.persistence.exceptions.IntegrityException
Descriptor Exceptions: 
---------------------------------------------------------

Exception [EclipseLink-48] (Eclipse Persistence Services - 2.4.1.v20121003-ad44345): org.eclipse.persistence.exceptions.DescriptorException
Exception Description: Multiple writable mappings exist for the field [SUBCLASSB.BASE1].  Only one may be defined as writable, all others must be specified read-only.
Mapping: org.eclipse.persistence.mappings.ManyToOneMapping[attrA]
Descriptor: RelationalDescriptor(test.entities.SubClassB --> [DatabaseTable(SUBCLASSB)])

Exception [EclipseLink-48] (Eclipse Persistence Services - 2.4.1.v20121003-ad44345): org.eclipse.persistence.exceptions.DescriptorException
Exception Description: Multiple writable mappings exist for the field [SUBCLASSB.BASE2].  Only one may be defined as writable, all others must be specified read-only.
Mapping: org.eclipse.persistence.mappings.ManyToOneMapping[attrA]
Descriptor: RelationalDescriptor(test.entities.SubClassB --> [DatabaseTable(SUBCLASSB)])

fyi: The equals and hashcode method are overwritten in all classes.

Solution

  • First of all, remove the @Inheritance annotation on Base. It doesn't serve any purpose.

    Then, try to explicitely define join columns for the ManyToOne association. It seems EclipseLink uses the same column names by default both for the embedded ID fields and for the many-to-one association with SubClassA. See http://docs.oracle.com/javaee/6/api/javax/persistence/JoinColumn.html for an example of using this annotation.

    Side note: composite IDs are both inefficient, and complex to handle. You should really consider using autogenerated, single-column IDs for all your entities. Everything would be much easier.