Google Web Toolkit uses Apache Ant to start a web container, either Jetty or Tomcat, along with the GWT application. Thus, to enable JReble for GWT in development mode, one should set ANT_OPTS environment variable accordingly.

Go to the GWT project directory, and create run-jrebel.sh file with the following content:

    #!/bin/bash
    export ANT_OPTS=-javaagent:$AGENT_PATH_UNIX
    ant devmode

Now use run-jrebel.sh to run your GWT application in development mode with JRebel enabled.