> if an applet can only communicate with the host from which it was
> downloaded, how is it possible to connect to a database server that is
> located separate from the web server?
> In our scenairo the database server is located behind the firewall and we
> certainly wouldn't want to store the data on our web server.
Hi Mike. You need a type-3 driver. A type-3 driver is all Java, like a type-4,
so it can be used in applets, but it doesn't connect *directly* to the DBMS.
Instead, it connects to an accompanying middle-tier which acts as a proxy,
connecting to the DBMS (using a type-2, type-4 JDBC driver or whatever, maybe
even vendor-specific C calls), and ferries your applet requests to the DBMS(se),
and sends results back to the applet.
This middle tier component *does* have to run on the webserver but it is free
to connect to any DBMS anywhere. Some smart middle-tire components (like WebLogic)
can do a lot more. The protocol between client applet and the middle-tier can be
secure (SSL or HTTPS to cross anyone's firewalls), and can supply connection
pooling for speed and management etc. The middle tier can even run queries
asynchronously to client requests, caching and sharing frequently needed data
so the DBMS is not burdened with multiple repeat queries from all the clients.
Joe Weinstein at BEA, the home of WebLogic
--
PS: Folks: BEA WebLogic is in S.F., and now has some entry-level positions for
people who want to work with Java and E-Commerce infrastructure products. Send
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