RE: Best practices: How to initialize state in EntityBean's superclass

[Conrad Chan]

I am doing something very similar to what you described.  My base class is
actually coded like a Entity bean so that it has all the ejbActivate,
ejbLoad, ejbStore etc.  Hence it is a self-contained entity bean which
handles its own state information nicely and my subclasses are not required
to re-declare those dummy functions if they do not need to.

Something like the following: -

abstract class MyBase implements EntityBean {
        protected transient EntityContext ctx;

        Vector states;

        /** My pseudo ejbCreate function */
        public void ejbCreate() { 
                states = new Vector();
        }

        public void setEntityContext(EntityContext ctx) { this.ctx = ctx; }

        public void unsetEntityContext() { this.ctx = null; }

        public void ejbActivate() {
                states = new Vector();
        }

        public void ejbPassivate() {
                states = null;
        }

        public void ejbRemove() {
                stats = null;
        }

        public void ejbLoad() { }

        public void ejbStore() { }
}

public class MySubclass extends MyBase implements EntityBean {

        String value;
        
        public Integer ejbCreate(String value) {
                super.ejbCreate();
        
                this.value = value;

                return null;
        }
}

Conrad

-----Original Message-----
From: Randahl Fink Isaksen [mailto:[EMAIL PROTECTED]]
Sent: Monday, February 19, 2001 4:18 PM
To: Orion-Interest
Subject: Best practices: How to initialize state in EntityBean's
superclass


Suppose you have two EntityBean classes A and B which share some common
functionality and state by inheriting from the same superclass S. Then, if S
has some member variable, say a java.util.Vector called "foos", which is
part of the persistent state of both A and B, my question is this: When
should "foos" be initialized?

I am positive that the ejbCreate methods of A and B could include an
instantiation like "foos = new Vector();" but if I use this model, I have to
remember to write this instantiation into every subclass of S, and if S has
many member variables (and many subclasses) that becomes error prone. - Not
to mention that if I add a new member variable to S I have to modify all
subclasses A, B, etc. to make their ejbCreate(...) instantiate this new
variable.

My own suggestion is to define a method in S, lets call it "void
instantiateS()" and have subclasses A, B, etc. invoke this method in their
ejbCreate(...).
I believe this method should *not* be the (no-arg) constructor of S as I
expect this contructor will be called everytime an instance of A or B is
loaded from persistant storage (which is unnecessary).

What are your suggestions?
What do you do when using inheritance in your beans?

Any comments would be appreciated.

Randahl.