<vendor>
The Inprise Application Server 4.1 comes with built-in support for entity
beans and their relationships with other entity beans and dependent. I am
not aware of other 'real' ejb server vendors providing the same standard of
support directly in their server without the use of an expensive O/R mapping
tool.
bean:
mapping one entity bean across multiple tables
mapping one entity bean across multiple databases
relationships:
one to one
one to many
many to many (xref)
We also support the use of references to dependent objects and beans in
finder methods:
<finder>
<method-signature>findByAddress(Address address)</method-signature>
<where-clause>
(:address.street1 IS NULL OR :address.street1 = street1) AND
(:address.street2 IS NULL OR :address.street2 = street2) AND
(:address.city IS NULL OR :address.city = city) AND
(:address.state IS NULL OR :address.state = state) AND
(:address.zip = 0 OR :address.zip = zip)
</where-clause>
</finder>
<finder>
<method-signature>findByContainer(Container container)</method-signature>
<where-clause>container = :container[ejb/container]</where-clause>
</finder>
mapping of dependent object to columns in table:
<database-map>
<table>Instructors</table>
<column-map>
<field-name>address.street1</field-name>
<column-name>street1</column-name>
</column-map>
<column-map>
<field-name>address.street2</field-name>
<column-name>street2</column-name>
</column-map>
<column-map>
<field-name>address.city</field-name>
<column-name>city</column-name>
</column-map>
<column-map>
<field-name>address.state</field-name>
<column-name>state</column-name>
</column-map>
<column-map>
<field-name>address.zip</field-name>
<column-name>zip</column-name>
</column-map>
</database-map>
Things are not so bleak if you look around. There are some vendors trying to
help developers move to entity beans with relatively little trouble and
performance cost, instead of recommending session beans + sql coding,
requiring that you run out and buy another expensive product or waiting for
ejb 2.0 compliance.
</vendor>
-William
"Habitability makes a place livable, like home. And this is what we want in
software-that developers feel at home, can place their hands on any item
without having to think deeply about where it is. Its something like
clarity, but clarity is too hard to come by".
Patterns of Software - Richard Gabriel
-----Original Message-----
From: David M. Karr [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, June 20, 2000 1:11 AM
To: [EMAIL PROTECTED]
Subject: Lack of Entity relationship management a weakness of pre-2.0
EJB?
Outside of much reading on the subject, I haven't had a chance to get
my fingers dirty with EJB yet. Therefore, please correct me on this
if I've misunderstood something.
It appears to me that the ability to build a robust distributed object
model with Entity Beans is hampered by the fact that (as far as I can
see) you can't easily map relationships between entities, both
aggregation and inheritance.
I get the impression that some of the work that went into the EJB 2.0
spec is attempting to rectify that, by specifying class/object entity
relationships in the deployment descriptor. It seems odd to specify
this here, but I guess it makes some sense.
Does IBM or BEA, or any other real EJB product, provide added value by
supporting relationship specifications? If so, do any of them come
close to what is being specified in EJB 2.0?
--
============================================================================
===
David M. Karr ; [EMAIL PROTECTED] ; w:(425)487-8312 ; TCSI & Best
Consulting
Software Engineer ; Unix/Java/C++/X ; BrainBench CJ12P (6/12/2000)
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