Apache Tomcat is proclaiming stability for the 16th release in its 5.5.x series. Version 5.5.16 strengthens the maturity of the platform as the march to the next major version begins. Tomcat is a widely deployed open source Java server technology considered "the servlet container that is used in the official Reference Implementation for the Java Servlet and JavaServer Pages (JSP) technologies," according to the Apache Software Foundation.

"We've had a number of stable releases and a good feedback from some large high-traffic installations," Shapira said. The predecessor 5.0 branch of Tomcat is still available for download from Apache, though the 5.5 branch is now clearly being well adopted and deployed.

Apache Tomcat Project Management Committee (PMC) member Yoav Shapira classified the 5.5.16 release as primarily a bug-fix release though at least some users should see some significant improvements. Those who utilize native Apache Portable Runtime (APR) connectors will notice improved stability and improved error reporting when errors do occur. Clustering features in Tomcat 5.5.16 now properly use session replication in cross-context environments such as portlet containers.

"I haven't measured this scientifically, but it seems that the majority of mailing list messages are about Tomcat 5.5 (and have been for a while), and that we get many downloads with each new 5.5 release," Shapira commented. The next major branch of Apache Tomcat though is just around the corner. Users of Java Management Extensions (JMX) management consoles and users who embed Tomcat in their application and use JMX to monitor it will notice additional information exposed via JMX.

The Apache Tomcat 5.5.x branch first appeared in September 2004 and the first stable release was the 5.5.4 release in November 2004. In the last year and a half, the 5.5 branch has strengthened and now quite stable and mature. "The 5.5 branch is winding its way into maintenance mode as we prepare for Tomcat 6.0," Shapira explained. "Tomcat 6.0 will be the version corresponding to the next servlet and Java Server Pages (JSP) specifications, servlet spec v2.5 and JSP spec v2.1 respectively."

The plan is for a Tomcat 6.0.0 release at the same time the new JSP specifications become final. New specification compliance isn't the only new thing users should expect in the 6.0.0 release. "Internally, we are continuing our push to a smaller, leaner, faster and more modular Tomcat," Shapira said. "We are working on improvements, indeed more like a rewrite to Tomcat's clustering to make it truly enterprise-class. We also continue to work on improving the documentation and growing the community. We've added a couple of new committers within the last months."