JavaRebel looks interesting ...
It's from ZeroTurnaround, seems to be an Estonian company.
Excerpt from the JavaRebel site:
"JavaRebel is a JVM plugin (-javaagent) that enables to reload changes made to Java class files on-the-fly, saving developers the time that it takes to redeploy an application or perform a container restart. It is a generic solution that works for Java EE and Java standalone applications."
Since they mention Java EE, it looks like JavaRebel might also work with the many Java web application frameworks out there, such as Apache Wicket.