J2ee project: ldap or rdbms for users?

Question

Hi,
I am about to design and implement a java-based product-quality (already have a working proof-of-concept) web service with the following components:
-ejb (session+entity) back end talking to a mysql db
-web client (browser) using servlets (possibly also JSF) to access session ejb.
-j2me personal profile client (using soap to talk to the back end) (PDA client)
While this service is not an online store, i suppose the design and requirements would be somewhat similar: personalized, scalable, secure and reliable. DB queries will be small in size (2-250k, vast majority 2-50k) but frequent. as with many personalized online services, users will have accounts which they will create themselves. Scalability will be important (potentially into several million users, though initially no more than 10,000), so some form of clustering will probably be needed.
Here's where i need some advice:
-should i utilize LDAP to store and access user information (e-mail, address, and encrypted passwords) or should i just these as columns to a table in my DB schema? what would be advantages of each approach?
-where should i store session information? specifically: currently i utilize stateless session beans, so session info is stored:
-in servlet's HttpSession when service is accessed through browser
-in Personal Profile application, when service is accessed via PDA
It seems to me this way i reduce load on the app server as well as network traffic (in PDA's case). Would storing session info in a stateful session bean be any better? Why?
thank you very much,
-nikita
ps. any to the point literature on end-to-end java-based architectures (online or printed)?

Answer 1

ps. any to the point literature on end-to-end java-based architectures (online or printed)?Maybe you could take a look at the J2EE blueprint resources at http://java.sun.com/blueprints/enterprise/index.html.