If you are building a web application you want to be able to create and edit Java and Scala code on the fly without having to stop and restart your web container for each code change.
JRebel to the rescue!
JRebel allows you to hot reload bytecode on the fly in your application without having to restart your web container.
Here's how you can use it in a web application with Scalate.
- Download JRebel
set your MAVEN_OPTS environment variable to point to where you installed the jrebel jar. For example:
export MAVENOPTS="-noverify -javaagent:$JREBELHOME/jrebel.jar”
run your web application in maven
mvn jetty:run
Now if your code is compiled by your IDE or a build process, the classes are automatically reloaded on the fly. Neat eh!
For example if you run the following in another shell
mvn scala:ccThen as you edit your scala code it will be recompiled using Scala's incremental compiler, then JRebel will auto-reload any recompiled classes.
Things to watch
We've found that if you use _scalate directory in the WEB-INF directory when running your web app using jetty:run JRebel really slows down the Scalate recompile step hugely; so its better to let Scalate use a work directory outside of the web application.
This should happen by default now; if not specify the scalate.workdir system property to be the work directory you want scalate to use. For example
mvn -Dscalate.workdir=/tmp/_scalate jetty:run