From my experience ( over 5 years in programming and over 3 years in Java server-side ) I found that there is a lot people who can put impressive experience, but missing basic knowledge. The field is changing rapidly. It is necessary to be familiar with latest specs,
J2EE design
patterns, third-party products. Studying for SCWCD certificate will at least bring your servlets/jsp knowledge up-to-date.
Besides the certificate, I found that it is very important to know following things:
1. Project modeling with UML ( from getting requirements to final implementation ).
2. Knowledge in software project management, such as "how to estimate how long will it take to complete the project", or "what to do when you can not complete the code within scheduled date".
3. J2EE patterns.
4. Open source tools such as
Ant,
JUnit, HttpUnit.
5.
JDBC and Database modeling.
Besides that communications skills, being able to listen and talk to people is always a must.