Correct me if I am wrong… I cannot find a reason in the EJB 1.0, 1.1, or 2.0 spec that CMP Entity attributes should NOT be declared of Interface type. Certainly, the *runtime type* must be RMI-safe, but must the *compile-time* type be RMI-safe, according to spec?
For example, consider:
public abstract class ABean implements javax.ejb.EntityBean {
...context and lifecycle methods...
//this is a CMP, not a CMR attribute, declared as an Interface type (java.util.List)
//it will be promoted to the remote interface
public abstract java.util.List getNonCMRAttribute();
public abstract void setNonCMRAttribute(java.util.List nonCMRAttribute);
}
This question arose during a project migration from VisualAge for Java 4.0 to Websphere Studio Application Developer 5.0.1.
The relevant mapping tools in VisualAge for Java and WebSphere Application Developer rely on user-developed “Custom Composer” classes, which convert between multiple database columns and single EJB attributes.
Composers in VisualAge for Java 4.0 enable CMP attributes to be of interface types like this (albeit in EJB 1.0/1.1, not 2.0), but Composers in WebSphere Studio Application Developer do NOT allow CMP attributes of interface types. In WSAD, all CMP fields must be of concrete types. Worse, the mapping tools work by introspecting the private field names of the CMP attribute classes, rather than introspecting the public getter/setter methods of the same classes.
What I had declared in VAJ were “virtual” fields in the Composer which the visual mapping tools could map 1-for-1 to database columns, but the “virtual” fields did not correspond to field names – or even real attributes – in the composed object. What the Composer did was just add all the virtual field values into an ArrayList, in the same order every time.
So, my mapping is broken and must be repaired. It’s easy enough to work around, but what I can’t figure is why IBM made WSAD more restrictive than VAJ. Which do you think is true:
· The new restriction is due to a section of the spec I just haven’t found
· The new restriction is purely arbitrary
· Having CMP attributes be of Interface type is such a poor design decision that IBM decided to make it impossible to do?
If the second, IBM should re-enable the mapping behavior previously enabled. If the last, the restriction should be in the spec.
TDD/AFCO Systems Group
Mellon Financial Corporation
