O JSP 2.2 e a sua parceira EL 2.2 são versões de manutenção da versão 2.1 para se adequar aos recursos da Servlet 3.0. Elas fazem parte da JSR245 http://jcp.org/aboutJava/communityprocess/mrel/jsr245/index.html (falar da jsr da servlet 3.0) que por sua fez faz parte da especificação do Java EE 6 (Falar da especificação JSR).
Servlet 3.0, JSP 2.2 e EL 2.2.
Asynchronous processing
Annotations Vs. Deployment Descriptor
Pluggability and Extensibility
http://today.java.net/article/2008/10/08/introduction-servlet-30
This topic is not included in the early draft of the 3.0 specification, as it is still undergoing discussions within the expert group. However, the proposal recommends providing the ability to log in and log out programmatically. New APIs will be added to HTTPServletRequest to enable this. The login method of HTTPServletRequest will allow the application or framework to force a container-mediated authentication. The logout method of HTTPServletRequest and HTTPSession allows an application to reset the authentication state of the request
http://java.dzone.com/articles/an-overview-servlet-30
Methods to add Servlets and Filters
Web fragments
