Rice Yeh wrote:
Hi Thomas, I am not familiar with ODMG but I will go to study it. One question needs your help, is it meant that in the mapping file for this DListImpl I do not need to configure the attribute element-class-ref for collection-descriptor tag?
That's correct!
If a class has a DList attribute you don't need to declare a CollectionDescriptor.
DListImpl is a first class citizen, that is it is treated a normal persistent domain class.
You simply specify a ReferenceDescriptor pointing to a DListImpl instance!
cu, Thomas
Regards,
Rice
--- Mahler Thomas <[EMAIL PROTECTED]> wrote:
Hello Rice,---------------------------------------------------------------------
Hi, I have been using OJB for some period. I am
taking a
project left by a partner that uses Hinbernate for persistence. So I start studying Hibernate.
Hibernate
has a mapping function called "any type mapping"
that
is defined as the follows:
"The <any> mapping element defines a polymorphic association to classes from multiple tables. This
type
of mapping always requires more than one column.
The
first column holds the type of the associated
entity.
The remaining columns hold the identifier. It is impossible to specify a foreign key constraint for this kind of association, so this is most
certainly
not meant as the usual way of mapping
(polymorphic)
associations."
This kind of mapping is quite useful when dealing
with
fields of java.lang.Object or interface. However,
as I
know, there is no such support in OJB.
That's not true!
OJB allows to build completely polymorphic mappings.
Just have a look at the o.a.ojb.odmg.collections.DListImpl class.
It is a list implementation that can hold elements
of arbitrary persistent
classes.
The trick is that we store serialized Identity objects as "pointers" to the actual objects. If you look at the DListImpl code you will see how easy it is.
cheers, Thomas
I try to study the source code of OJB, but am still not able to figure out the way to modify it (The xml mapping handling code is a little hard to understand, just wonder if it is possible to re-write it with Jibx
to
make it more concise).
Regards, Rice
__________________________________ Do you Yahoo!? Exclusive Video Premiere - Britney Spears http://launch.yahoo.com/promos/britneyspears/
---------------------------------------------------------------------To unsubscribe, e-mail:
[EMAIL PROTECTED]
For additional commands, e-mail:
[EMAIL PROTECTED]
To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
__________________________________ Do you Yahoo!? Protect your identity with Yahoo! Mail AddressGuard http://antispam.yahoo.com/whatsnewfree
--------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
--------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
