If you need to use EJB, use a session bean and JDBC.
That way you can implement and SQL query you want.
Don't use entity beans in this case.
Cheers,
Frank Sauer
The Technical Resource Connection
Tampa, Fl
http://www.trcinc.com
> -----Original Message-----
> From: A mailing list for Enterprise JavaBeans development
> [mailto:[EMAIL PROTECTED]]On Behalf Of Tim Fox
> Sent: Thursday, May 18, 2000 11:18 AM
> To: [EMAIL PROTECTED]
> Subject: Object-relational problem
>
>
> Here's a problem I've been chewing over for a while now and
> haven't come
> up with a satisfactory solution.
> It's one of the classic object-relational problems.
>
> Here's a simplified description (please note that this is a fictitious
> example - I've simplified it for clarity)
>
> I have 2 ejbs: a Customer and an Address.
> The customer has a home address.
>
> I'm displaying a list of all customers satisfying certain
> criteria along
> with their home address on a web-page.
>
> There would be one customer & address per line.
>
> This would look something like:
>
>
> Customer Name Customer Address
> =========== =============
> Joe Bloggs 1 High Street, Newtown
> John Doe 23 Synchronicity drive, London
> Jane Doe 2 Big Street, Badville
>
> Now the page is hit a lot so I want to get the entire list using one
> query - this is pretty easy in SQL - a simple join across the customer
> and address tables.
>
> The last thing I want to do is query for all the customers, then, for
> each customer query for the address - this would cripple the system
> since I'd have a new query for each row of the page.
>
> However, if I'm using ejb then it seems I could either:
> 1.
> Use a finder method to get the list of customers given the criteria,
> then...
> For each customer in the list, use the findByPrimaryKey() (or
> whatever)
> method to find the address.
> This is probably the worst solution since it would probably
> involve a db
> query for each customer address.
>
> 2.
> Use a finder method to get the list of customers given the criteria,
> then...
> Use a finder method to get the list of addresses given the criteria.
> This basically involves running the same (or very similar)
> query twice -
> once in the Customer finder method, and once in the Address finder
> method.
> This, although better than 1) seems very wasteful
>
> 3.
> Do the query once, and pass the resultset into the finder
> methods of the
> customer and address objects - don't know if this is possible
> though due
> to remote calls and marshalling of the resultset
>
> 4. Create a denormalised ejb called AddressCustomer which is an
> amalgamation of the Address and Customer objects. Yuck!!!
> Then I also end up with an AccountCustomer, AccountCustomerStatement,
> ProductManufacturerSupplier etc. ad infinitum objects.
> Basically the nice OO model gets shot to f*** !!
>
> I'd been interested in any comments/solutions people have implemented,
> as this is really bugging me
>
> (BTW if I wasn't using ejb I'd use 3) since I wouldn't have any remote
> calls problems).
>
>
> Cheers
>
> --
> Tim Fox (��o)
>
> Senior developer
> Hyperlink plc
> http://hyperlink.com
>
> email: [EMAIL PROTECTED]
> phone: +44 (0) 207 240 8121
>
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