Before I started to program the project, I read
lots of articles of javaranch but was hard to decide
which way to go. After reading the following article,
I decided to go with 3 tier. This article is a classic argument
between 2 and 3 teir.
https://coderanch.com/t/184224/java-developer-SCJD/certification/Should-lock-methods-callable-client If you don't have time to read through the whole article,
the conclusion is 2 or 3 tier is OK to sun. If you don't want to handle
connection loose and don't want to send lock cookie to your client,
you can go with 3 tier, like what I did.
Steve Taiwan<br />SCJP 1.2, SCJD 1.4, SCWCD 1.3, SCBCD 1.3, OCP 8i DBA, SCEA