Andreas,
The spec does not require mandatory passivation of bean instances at the end
of transactions. As a matter of fact, the spec describes three different
commit options. Option A (page 122, EJB 1.1) describes the exact scenario
you are prohibiting. Using CMP or implementing BMP, of course, doesn't have
anything to do with the above.
Imre Kifor
Valto Systems
-----Original Message-----
From: Andreas Vogel <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
Date: Friday, May 14, 1999 9:09 AM
Subject: Re: EJBs and the internet
>Robert,
>
>you need to look carefully at the life cycle definition for entity beans.
An entity
>in the pool is not associated with any data. The association happens at the
begin of
>a transaction, that is ejbLoad(), at the end of the transaction the data is
written
>back into persistence storage (ejbStore()), the entity returns to the pool
and looses
>the association with the data. The next client goes through the same cycle.
The
>advantage of the approach is data integrity, the disadvantages is
performance
>overhead. A container may do clever things when CMP is used.
>
>Cheers,
>
>Andreas
>
>Robert Krueger wrote:
>
>> Andreas Vogel wrote:
>>
>> >
>> > Entity beans are specifically targeted towards transactions. Caching is
a value
>> > add of CMP implementation BMP prevents you from caching.
>> >
>>
>> Why would that be? I thought a container could keep entity bean data in
>> memory no matter if CMP or BMP? My understanding was that say client 1
>> requests an entity bean instance with PK x which is not in main memory.
>> It is retrieved from the DBMS (CMP or BMP) and instantiated in main
>> memory. Then client 2 also requests the entity with PK x, which then may
>> still be in main memory. Where is the difference between CMP or BMP
>> here? It may very well be that I'm misunderstanding the spec as I am not
>> an expert. Could you please enlighten my on that point as it seems to be
>> a very important factor in designing an EJB application using entity
>> beans with BMP with acceptable performance.
>>
>> Thanks,
>>
>> Robert
>>
>> --
>> (-) Robert Kr�ger
>> (-) SIGNAL 7 Gesellschaft f�r Informationstechnologie mbH
>> (-) Br�der-Knau�-Str. 79 - 64285 Darmstadt,
>> (-) Tel: 06151 665401, Fax: 06151 665373
>> (-) [EMAIL PROTECTED], www.signal7.de
>>
>>
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>--
>"Programming with Enterprise JavaBeans, JTS and OTS" is now available.
Collect all
>three!
>www.wiley.com/compbooks/vogel
>
>
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