I just have one question: what are the criteria of judging a servlet engine?
Ease of Use.
Try Resin. It is the bomb!
From Resin site...
Resin� is a cutting-edge XML Application Server. It serves the fastest servlets and JSP. It has the fastest XML and XSL engine. Its new Hessian web services bridge EJB power with multilanguage flexibility.
The rebelutionary a.k.a. Mike Cannon-Brookes wrote some good stuff on how to compare servlet containers... Follow this links there is some real good information to be found.
The speed of development with Orion or Resin blows Tomcat out of the water for me. To continue the metaphor - imagine a modern, nuclear powered submarine versus a mid-1940's U-boat
What makes a good App server?
What app servers need is developer performance!
David Johnson (I'm going to have to start using surnames despite the impersonality, there are just too many Davids!) has posted a response to my Is Tomcat Crap? article called, surprisingly enough, Tomcat is not crap.
He brings up three main points:
Fast edit-compile-deploy loop - You can't get faster than Orion (and I think Resin is the same [only better]). Web app automatically deploys, changing any JSP file (even included ones) causes recompilation, touching web.xml auto-redeploys, everything in state (session, application scopes) is kept (no logging in every time you recompile like Tomcat - argh!) and Orion (and Resin) will even compile your beans for you (change the source file and reload the JSP page - it compiles the bean automatically). This covers everything David asked for!
Make it really easy to zoom in on errors - Well, again both Orion and Resin provide line numbers in your JSP file which makes it easy to fix problems. As far as I can get it working, Tomcat only provides stack traces in the generated Java class - which is next to useless. Again, this covers everything David asked for!
Make it really easy to configure the server - This one is quite subjective I think. I love Orion and Resin's configs - they are very easy, simple XML files. The process is simply edit the file, and the server automatically reconfigures itself when you save. I'm not sure how Tomcat works here - although the XML config file did seem perfectly understandable to me. As for GUI tools, I don't like them (too slow!) but some might want them - see JSR-88.
"None of the current crop of servers really come close to supporting all of these things." To use a famous Aussie phrase - "Bullshoot mate!" [editied RMH] See above - both Orion and Resin do almost everything you've asked for!
"The Tomcat developers deserve our support and our thanks. They are doing a great job. I've seen Tomcat improve by leaps and bounds over the last year and it will continue to improve - I do not doubt that one bit." I agree completely - I hope Tomcat keeps improving, which is partly why I started this all. My only problem is that too many Tomcat users don't use other servers (as can clearly be seen above!) and therefore don't know what they're missing (or where Tomcat is lacking).
[ October 15, 2002: Message edited by: Rick Hightower ]
Resin is very good in this capacity as well but obviously can't compare to the cost of OSS project like Tomcat or Jetty.
Of course TOC of ownership of open-source products can still be greater than commercial products so one can't judge based on sticker price alone.
[ October 16, 2002: Message edited by: Chris Mathews ]