Application server - to use or not use?

Question

Typically we use WebLogic or JBoss to deploy our apps. I understand that when using open source solutions like Spring you can develop your app and run it on a simple servlet container like Jetty. So the question would be why even bother with an app server?

Answer 1

• Advanced features - like transactions, security integration, pooling, hi-perf queuing, clusters.
• Performance (weblogic has a hot JVM)
• operational and administrative interfaces.

beyond that... I don't know?

In most cases, YAGNI.