J2EE/ Web 2.0 Discussion from IBM
Web 2.0 applications developed using standard Java™ Platform, Enterprise Edition 5 (Java EE)-based approaches face serious performance and scalability problems. The reason is that many principles that underlie the Java EE platform’s design — especially, the use of synchronous APIs — don’t apply to the requirements of Web 2.0 solutions. This article explains the disparity between the Java EE and Web 2.0 approaches, explores the benefits of asynchronous designs, and evaluates some solutions for developing asynchronous Web applications with the Java platform.
http://www.ibm.com/developerworks/web/library/wa-aj-web2jee/