My comments below:
Regards,
Murali Krishna Devarakonda
----- Original Message -----
From: Chris Raber <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, October 01, 1999 7:04 AM
Subject: Re: Doubts about Entity beans, Should we use them?
Muly,
I don't think you can categorically say BMP is bad/slow. Tools like Cocobase
will generate efficient third tier interactions with regard to finders to
address the issue you point out below.
My view:
Entity Beans to add remote component overhead, but this isn't too bad if
entity beans represent a coarse grained component with sub-objects which are
non-bean.
<SmallFry_NoAuthority_YetHighlyOpinionated_MURALI>
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^^^^^^^^^
</SmallFry_NoAuthority_YetHighlyOpinionated_MURALI>
CMP is a great idea, but the spec needs work so that implementations across
vendors are more even/portable (e.g. relationships to non-bean sub objects
need to be standardized, issue with finders need to be addressed...). As I
understand it, these issues are to be addressed by the 2.0 specification.
<SmallFry_NoAuthority_YetHighlyOpinionated_MURALI>
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^^^^^^^^^
MY THOUGHTS EXACTLY!
Thanks Chris!
-Murali
</SmallFry_NoAuthority_YetHighlyOpinionated_MURALI>
In the mean time session beans directly to persistently mapped objects, or
session beans to BMP entity beans are decent solutions. A tool that helps
with the OR mapping in either case is a big help.
-Chris
----------------------------------------------------------------------
Chris Raber, Director Professional Services, GemStone Systems Inc.
100 West Big Beaver, Suite 200, Troy, MI 48084
phone: (248)-680-6691, fax: (248)-680-6689,
email: [EMAIL PROTECTED]
web: http://www.gemstone.com/
----------------------------------------------------------------------
> -----Original Message-----
> From: Muly Oved [SMTP:[EMAIL PROTECTED]]
> Sent: Thursday, September 30, 1999 10:58 AM
> To: [EMAIL PROTECTED]
> Subject: Doubts about Entity beans, Should we use them?
>
> Hi
>
> For design a non-trivial distributed database application,
> to be implemented in Application server.
>
> Here some guidelines and ideas I picked during my searching, I maybe wrong
> :)
>
> * Don't expose entity beans to the clients:
> It is recommended that the client will talk with session beans and the
> session beans will talk with the entity beans.
>
> This way the client request for operation form the session beans and the
> session bean do all the work, by access to multiple entity beans and other
> session beans and work as a facade,
> hiding from the client the server object schema complexity
> and collect the operations a client need to do to one operation
> those avoiding network traffic.
>
> * Bean managed persistence is BAD:
> Also there is a clear and easy framework how to write the code for BMP.
> It is BAD to use it if performance is important.
> Using BMP will be VERY inefficient and will generate many small SQL
> operations.
>
> If you need operation like
> SELECT FNAME,LNAME FROM EMP
>
> BMP will generate:
> SELECT PKEY FROM EMP
> And then for every record in the table
> SELECT FNAME,LNAME,ADDRESS,... FROM EMP WHERE PKEY=?
>
> * Component managed persistence is problematic:
> Also theoretically the container can do some optimization to overcome
> the BMP problem, there still a problems There is no standard how to
> specify mapping to the component (Fields, and Find code)
> Most of the implementation are trivial and does not allow complex mapping
> between beans and database.
> Those limitations will be improved in the future, as technology
> mature, but it will certainly take time.
>
> But even if CMP is perfect, why we need them?
>
> If the client does not talk with them, They only accessed internally to
> the server.
>
> Entity beans are heavy they required stub, skeleton, home, component side
> object the bean itself and more,
> I may be wrong here in the list of objects required but I think
> Entity Beans are still heavy compared to simple java classes.
>
> So:
>
> Does entity beans are useful (either now or in the future) for real world
> database application?
>
> Maybe what is required is a different standard that fit better to map Java
> objects (without the remote features) to databases
> something like TopLink, JavaBlend or Cocobase?
>
> Meanwhile is there some design patterns that can be used to design today
> persistence objects that can provide some acceptable performance with
> current technology and are easy to migrate once a better one come?
>
> Any other ideas how to implement domain logic as objects?
>
> Regards,
>
> Muly.
>
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