Peter Miller wrote:
> Jeff,
>
> The whole idea about this architecture, commonly call multi-tier or n-tier,
> this that there is a separation between client presentation logic, business
> logic and state persistence, in that order. So clients should deal only in
> presentation issues, and request business process execution of the server.
> It, in turn, validates and manipulates various objects and they persist
> their state to a store (typically an RDBMS).
>
> So, the answer is, clients should not access JDBC at all, never!
I'm not sure I agree with this statement. Before EJB a lot of people, including
myself, were busy writing database gateways or brokers that allowed clients to
obtain thin JDBC driver connections that were multiplexed by a central server.(
2-Tier was still king at that time and even Java-CORBA as in its infancy.) In
other words the JDBC-broker ensured that JDBC connections were pooled and
shared across clients, which make 2-tier systems more scalable. As a matter of
fact, the Weblogic was originally an independent company that got its start (I
believe) as a JDBC driver and JDBC-broker vendor. They provided a lightweight
specialized JDBC driver that communicated client request over the network to a
broker, which then redirected the requests native JDBC drivers.
Anyway, using JDBC directly from clients in a 2-tier system is still a viable
solution if you use the right technologies. 3-tier is great, but its not for
everyone.
Richard
--
Richard Monson-Haefel
Author of Enterprise JavaBeans, 2nd Edition (O'Reilly 2000)
Co-Author of Java Message Service (O'Reilly 2000)
http://www.EjbNow.com
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