> -----Original Message----- > From: Richard S. Hall [mailto:he...@ungoverned.org] > Sent: Thursday, March 29, 2012 6:53 PM > To: dev@felix.apache.org > Subject: Re: Enhanced Apache Felix / JRebel integration > > On 3/29/12 6:45, Robert Munteanu wrote: > > Hi, > > > > I am looking into enhancing the integration between Apache Felix and > the JRebel [1] JVM agent. If you're not familiar with JRebel, it's a > java agent which allows classes loaded into the JVM to be redefined as > soon as they are recompiled e.g. in an IDE. For more information about > its features, see [2]. > > > > JRebel already has basic support for Apache Felix by allowing classes > for a deployed bundle to be reloaded without requiring a bundle > repackage and reinstall. > > > > What I want to contribute is support for components managed using > declarative services. The basic principle is that given a bundle which > contains service components descriptors, watch for changes to those > component descriptors and refresh the components when the respective > descriptors have changed. > > > > I have taken a quick look at both JRebel and Felix to see how an > implementation should look like. JRebel offers support for detecting > class changes, but not generic filesystem changes. Therefore I'd have > to rely on Felix code ( in org.apache.felix.scr ? ) to detect > > > > - when a bundle with component descriptors is deployed and start > watching for changes to the descriptors > > - when changes to the mentioned descriptors are detected refresh the > components > > Is there some reason you need to refresh at the class level as opposed > to the bundle level? If the bundle level was sufficient then it seems > like this scenario becomes much simpler.
My intention is to first refresh the whole bundle when a component descriptor is changed. If needed I will look into fine-grained refreshes but that's not on my immediate plan. > > Also, what do you mean by "refresh the components" above? Do you > specifically mean re-load the class bytes? If so, how do you know that > changes to the descriptor require re-loading the class bytes or are you > just assuming it does? By refresh I mean a deactivate/activate operation taking into account whether a component is marked as immediate or not. Fortunately refreshing the actual class bytes is handled by the 'core' JRebel functionality when the class file changes. > > Additionally, it seems you might be confused about the responsibility > of > some tasks. For example, SCR doesn't look for changes in component > descriptors at all, it simply listens for bundles to be activated. > Listening to changes in the component descriptor would have to hook > into > the build process somehow. By and large, none of the Felix subprojects > are involved in the build process other than the Maven Bundle plugin. I have considered hooking into the maven-bundle-plugin as well, but I have no idea on how to notify Felix that a bundle needs to be refreshed or even send a custom event which I can handle myself. Thanks, Robert > > -> richard > > > > > I would like to validate that this is at all possible within Apache > Felix and to ask which are the best places to start looking for adding > the JRebel functionality. Any thoughts/pointers on how to best start > developing this would be greatly appreciated. > > > > > If this is feasible, I intend to develop this as a separate JRebel > plugin and contribute it to the Apache Felix project. > > > > Thanks, > > > > Robert > > > > [1]: http://zeroturnaround.com/jrebel/ > > [2]: http://zeroturnaround.com/jrebel/features/ > >
