Hi...this is what was written in java.sun.com
RonCrawford_II: Why is the SingleThreadModel interface and option in
JSP when the
Java platform offers the synchronized keyword? What are the benefits of placing synchronization on the JSP engine?
Marty: Well, SingleThreadModel gives the server more flexibility than you would have if you manually synchronized all your code in service or _jspService. For example, a server can queue up requests to a single servlet instance or make multiple servlet instances and send requests concurrently (as long as a single instance gets only one request at a time). That all being said, I do agree that in general it is better NOT to use SingleThreadModel and to synchronize access to shared data yourself.
bye dude