> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
> Subject: Re: [Hibernate] questions about polymorphism
>
<snip stuff="good, thanks!"/>
> >> Since the subclass is
> completely described this way, is the separate mapping file for the
> subclass
> redundant? <<
>
> You should not have a seperate mapping file for a subclass.
I thought I was out of the weeds, but I guess not yet.... Another Q:
In removing the separate mapping files for a subclass, it seems that I lost
my ability to reference them directly. In reference to the contrived example
below, I should like to be able to recover a reference to one object that
contains a collection of the superclass objects. I would hypothetically
iterate over the objects and decide what to do (although I don't generally
use instanceof like this):
/**
* @hibernate.class
*/
public class Super {
private Long id;
/**
* @hibernate.id column="id" unsaved-value="null"
generator-class="native"
*/
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
}
/**
* @hibernate.joined-subclass
* @hibernate.joined-subclass-key column="subKey"
*/
public class A extends Super {
private B b;
/**
* @hibernate.many-to-one
*/
public B getB() {
return this.b;
}
public void setTheContact(B b) {
this.b = b;
}
}
/**
* @hibernate.joined-subclass
* @hibernate.joined-subclass-key column="subKey"
*/
public class B extends Super {
private java.util.Collection supers;
/**
* @hibernate.set role="Super" lazy="true"
* @hibernate.collection-one-to-many class="Super"
*/
public java.util.Collection getSupers() {
return this.supers;
}
public void setTheContact(java.util.Collection supers) {
this.supers = supers;
}
}
public static void main(String[] args) {
// set up session
// ...
A a = (A) session.load(A.class, new Long(1));
B b = a.getB();
Collection bigBag = b.getSupers();
for (Iterator it = bigBag.iterator(); it.hasNext();) {
Object o = it.next();
if (o instanceof A) {
//...
} else if (o instanceof B) {
//...
}
}
}
So here are some questions/assertions i'd like to understand better:
1) I believe this code generates valid descriptors, but I am still fuzzy on
the use of the <key/> in a joined subclass since I haven't made a full
round-trip yet. I believe this is going to create a column in my superclass
which is going to get filled by default with the fully-qualified class name
of the subclass. In this case, using the same <key column="subKey"/> for
each subclass is correct since a column named subKey will be created in table
Super. (btw, this is what I was doing with EJB entities up until last week,
with all kinds of crazed instantiator overrides built on home interface
inheritance... it was just shy of unmanageable!)
2) On the other hand, this code doesn't pass muster with the runtime
descriptor compilation because A and B cannot be directly referenced. It
seems then that A and B could have both @hibernate.class and
@hibernate.joined-subclass, but that would generate separate mapping files,
going against your earlier negation of this. It's manageable with XDoclet
since they don't need to be kept in sync, but maybe not ideal. The question
is, will it work robustly in practice?
3) It seems that XDoclet could be expanded to better understand inheritance
relationships when deciding what to generate. For instance, if I change one
of my subclasses, the superclass mapping does not get regenerated. It could
be solved by having all of the mappings in a single file, but there a
reference in the manual saying that the best practice is to place each class
mapping in its own file for team environments. Unless there is experience to
the contrary, I'd like to change XDoclet to generate a single mapping file
(or at least do so by a subtask switch). It makes sense because
programatically determining inheritance in XDoclet is an n^2 operation,
regenerating the entire file skips the step and is not a detriment in a team
environment because developers don't check in the descriptor files anyway.
thoughts/comments/input welcome and appreciated!
-b
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