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.
Please follow this link for a demonstration screen cast -http://www.zeroturnaround.com/javarebel-demonstration-screencast/
Source: http://www.zeroturnaround.com/