Faster Java based WCMS development

As I’ve mentioned in my last technology post, I’ve now also tried to use JRebel with a WCMS system, namely Day CQ5.3. It’s based on Apache Sling which uses Apache Felix as OSGI Container and a JSR-283 compliant java content repository to persist it’s content/data. Our basic approach to write components, services, tags and so on is to add all logic (java classes) into a OSGI bundle and deploy that on Felix. All the stuff that is needed to generate the view (jsp, xslt) is saved directly into CRX, the JCR of CQ5. So to load a page, two different classloaders are used, first DynamicRepositoryClassLoader (Sling/JCR) which loads the jsp out of the repository and then instantiates a class (for example for a tag) that is served by the OSGI bundle, for which FelixModuleClassLoader is used.
As you can read on www.zeroturnaround.com, Felix with JRebel is beta support, so why not try to use it with CQ at least to eliminate the deploy process of the OSGI bundle?

The result first: after a couple of mails with Lauri Tulmin from zeroturnaround, it finally worked.

My configuration:

• In my maven project, I saved rebel.xml under src/main/resources, it contains the path to the classes folder of my eclipse workspace.
• In the pom.xml of the project, I had to add the following line
  <Import-Package>*,org.apache.sling.jcr.api;version=2.0.4,org.apache.sling.jcr.resource</Import-Package>
  to the maven-bundle-plugin configuration
• In the start script of CQ, I added the following parameters:
  CQ_JVM_OPTS="-noverify -javaagent:<path to jrebel>/jrebel.jar -Drebel.packages_exclude=sun.reflect"


The parameter -Drebel.packages_exclude=sun.reflect is a kind of a workaround of a JRebel bug, in the newest version it shouldn’t be necessary anymore.

With this configuration I can save my java files in Eclipse, reload the page and the changes are immediately viewable.
For now, this configuration isn’t tested in productive work. We plan to use it in the next couple of weeks and will for sure find some pitfalls… (hopefully not, but you know… 😉 )

I’ve also tried to write an own JRebel plugin to patch the Sling/JCR Classloader, but at the moment it’s not that stable to use it in productivity. You can find some Integration-Javadocs about that on the webpage of zeroturnaround.