Chip,
Thanks for the information. Do you have any "code samples" which are not proprietary
that I can take a look at? Also I have some questions.
I have developed a ClientSessionManager object which maintains a list of the clients
using the client Identity. Each ClientSession object is a SessionBean which is
created by an RMI Server component upon User login. The EntityBean's can then lookup
up the appropriate ClientSession within their methods. The ClientSession SB's
implements the SessionSynchronization interface and creates the UOW for the user
within the afterBegin() method and commits and/or rolls back the UOW in the
beforeCompletion() method. Below are a couple of specific questions:
1. You say you store the user's UOW within the User's context. How do you do this?
I wasn't aware that you could put data in the User's context. That's why I created a
ClientSessionBean to store the client's state information.
2. My thought was to have the ejbCreate() method of the EB's look up the
ClientSession and register "empty" objects at that time and get the PrimaryKey. TL
should be able to return a new PrimaryKey (next identifier) even though there is no
data in the object. Then when EB's ejbStore() method gets called, you can merge the
copy of the real object into the ClientSessionBean and corresponding UOW. Can you
think of a reason why this might not work? I would think this would eliminate the
need to keep track of the changed domain objects for each Entity Bean, since the
corresponding ClientSessionBeans and associated UOW's would deal with the issue, won't
they?
3. Was the effort worth the result? I would love to just use CMP, but given my
multiple EJB Server requirement and lack of a standard Container mechanism, I think
TOPLink is probably the best way to go. However, it's not too late to change
directions, and if you have any reasons why we should not continue with this approach
I would love to hear them.
4. How did your overall system perform? I don't know all of the details and overhead
of TOPLink and EJB, but TL says to expect a 20% degradation and EJB has overhead, so I
would expect some. Did you find that the "developmental cost savings" and TL's
UnitOfWork and caching mechanisms performance saving make up for the overhead?
Thanks,
Gary
>>> Chip Wilson <[EMAIL PROTECTED]> 09/08/99 08:25PM >>>
Hi Gary,
I implemented a large system currently in production using BMP and TOPLink for Java
(not WebLogic). I can't go into all the gory details, but in short this is what we
did:
Implement all transactions (system operations) on session beans as TX_REQUIRED.
Any entity bean method that modifies the domain should be set to TX_MANDATORY.
Set all bean methods everywhere to CLIENT_IDENTITY.
Provide a user login method on a session bean.
Implement a user context dictionary that keeps track of all the currently connected
users by their Identity/Principle.
When a user logs in, create a TOPLink client session for them.
Implement the SessionSynchronization interface in all session beans.
During afterBegin, look up the TOPLink client session by the caller's identity, create
a unit of work for the user, and store it in the user's context. Also register a
transaction synchronization adapter using the server's JTA implementation (or
equivalent).
As entity beans change, keep track of the changed domain objects in a collection for
each entity bean.
During every ejbStore, look up the UOW by the caller's identity and merge the changed
objects into it.
When the transaction adapter gets a prepare call, commit the TOPLink unit of work. If
an exception is thrown, vote to rollback.
There are a lot of little things you will have to deal with, like the fact that
ejbCreate has to return the primary key of a new entity, but (if you are using
sequence generators in the database) TOPLink won't generate the PK until the
transaction is committed. We were able to solve al these problems, but I can assure
you that the overall task of integrating TOPLink with BMP is non-trivial.
Most of the code can be implemented in abstract super classes, so that individual
bean's don't know anything about all this.
Good luck!
--Chip
Gary Swatton wrote:
> Hi Chuck,
>
> Are you using TOPLink (TL) for Java 2.0 or TOPLink for WebLogic? Are you utilizing
>UnitOfWork (UOW) within your EntityBeans (EB) or just utilizing TL's Sessions?
>
> I haven't been able to figure out how to set up my EB's to utilize UOW's (because
>EB's are shared and by definition, UOW's are one per user).
>
> I've tried to set up the UOW's encapsulated inside a SessionBean (SB) per client,
>but don't know how to identify which Client is modifying the EB from the Server EB.
>
> Any insight would be helpful.
>
> Thanks,
>
> Gary
>
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