"Apache Tomcat is open source software that implements Java
Servlet and JavaServer Pages, enabling sites to run Java servlets
(like server-side applets) and Java-based dynamic content. he last
major release (6.0) was in December 2006, with the most recent
stable version (6.0.29) coming out last July. Version 7.0.2, which
supports Servlet 3.0, JSP 2.2, and EL 2.2, has been available in
beta for a couple of months.
"Note that 7.0.2 is still in beta, so it's not a good match for
production sites just yet. The Apache Group has specifically
recommended against using it for business purposes right now; the
changes are large enough that they want some real-world testing
before it's released as production code. However, it's well worth
installing on a non-production server to test it out. Note also
that if you want to use Servlet 3.0 or JSP 2.2 apps, this is your
only Tomcat option.
"As well as the support for Servlet 3.0, JSP 2.2 and EL 2.2,
there are various other improvements, including support for
aliases, memory leak protection, and a cross-site forgery
prevention filter. The provision of aliases means you can now have
server-wide .war files or static content directories that you can
share among applications. You no longer need to wrap them up in
each app archive. This is particularly useful for common images,
error redirects or other similar pages. The memory leak prevention,
which has been backported to Tomcat 6 already, is neat."