Hi Matthew,
I've done that to introduce @Id and @Version if not provided on JPA classes. You need to use the -XhasMember compiler option, and then I wrote it this way :

public aspect InstallIdByDefault {

        /**
         * Marker interface for beans receiving the default id.
         *
         * @author Simone Gianni <[email protected]>
         */
        public static interface WithDefaultId {
                
        }
        
        declare parents : ((@Entity *) && !(@NoId *) && !hasmethod(@(Id||EmbeddedId) 
public * get*()) && !hasfield(@(Id||EmbeddedId) * *)) implements WithDefaultId;
        
        /**
         * The default provided id field.
         */
        private long WithDefaultId.id;
        
        /**
         * Getter for the default id.
         * @return The entity id.
         */
        @Id
        @GeneratedValue
        public long WithDefaultId.getId() {
                return id;
        }
        
        /**
         * Setter for the default id.
         * @param newId The entity id.
         */
        void WithDefaultId.setId(long newId) {
                id = newId;
        }
        
}

You can find the complete aspects (also for @Version) here : 
http://svn.apache.org/repos/asf/labs/magma/trunk/database-jpa/src/main/java/org/apache/magma/database/openjpa/

Simone



Matthew Adams wrote:
Hi all,

I was wondering how it might be possible to achieve what I'm calling a
conditional inter-type declaration.

Here's a simple auditing example.  For a JPA entity, I want to
introduce a @PrePersist method if and only if the target class doesn't
have one because it's an error to have multiple @PrePersist methods on
an entity.  If it already has a @PrePersist method, I want to execute
advice after the target instance's @PrePersist method is invoked by
the JPA implementation.  Same for @PreUpdate.

The example below will work for Person, but not for Document --
Document will end up with two @PrePersist methods.  How can I refactor
this to work for both?

========
@Entity
public class Document {
  // ...
  @PrePersist
  private void prePersist() { /* ... */ }
}
========
@Entity
public class Person {
  // ...
}
========
// works only for an @Entity that DOES NOT define a @PrePersist or a
@PreUpdate method
public aspect AuditingItd {
        private interface Auditable {
        }

        declare parents:  (@javax.persistence.Entity *) implements Auditable;

        @Column(name = "updated")
        private Date Auditable.updated;

        @PrePersist
        private void Auditable.auditablePrePersist() {
                updated = new Date();
        }

        @PreUpdate
        private void Auditable.auditablePreUpdate() {
                updated = new Date();
        }
}
=========

-matthew



--
Simone Gianni            CEO Semeru s.r.l.           Apache Committer
http://www.simonegianni.it/

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