What is scalable, fast, application server to use for developing services written in java

I am trying to develop some web services. I want to know a application server that is scalable, fast, has high throughput, and is not too complex. Also it doesn't need to implement J2EE, but the services will be written in java.

From stackoverflow

• Id use tomcat if i were you. everyone uses tomcat, it has good support, its easy to set up, and is compatible with Java 5 EE, which means you can always ditch it and use another compatible container

  Owen : Agree - Tomcat has always been great to me for developing.

• Jetty

• You might want to have a look at OpenGSE, the Google Servlet Engine. The fact that it hosts GMail and Google Calendar should be enough to speak for its scalability :)

  (Okay, so I'm not going to claim that GSE is the sole cause of GMail's scalability, but it clearly works...)

• I like to roll my own with lipermi and then use Java Service Wrapper

• JBoss has always been wonderful for me to use when writing my Web Services.

• Tomcat, Jetty, Resin, JBoss, GlassFish.

  It's all the same, because scalability is a quality of your software and not of the server it runs.

• G-WAN is by far the fastest.

  : And by far the most widely used.