Thursday, May 20, 2010

A custom plug-in system for web applications

Recently I was trying to put together a plugin system for web applications. The idea is similar to Eclipse plugins. Where you bundle your extension in a jar and then drop them in Eclipse-Home/plugins folder, restart Eclipse and you are ready to use it. Note that Eclipse plugins are OSGi plugins.

So my initial effort was to see if I could build a pluggable web application with OSGi. After few experiments with Equinox (the Eclipse OSGi engine) and Felix, I moved on to check out Spring DM as well as Spring DM server. But all I all I felt that

  • OSGi / DM involves significant learning curve.
  • The web server bundles are “probably” not of enterprise strength.
  • Still trying to gel with JEE.
  • Significant extra effort required to port applications to OSGi platform.

All in all  OSGi / DM has to go few more miles before we build Enterprise server apps using those containers / bundles. But its a very good start and promises a lot in the future.

So what to do? I started digging dip into Spring framework for a while and soon came up with an idea of a simple plug-in system for web applications. This plug-in system should allow you to package your application components(controllers,business objects, data acccess)  in a jar file with mandatory Spring config file. This jar file should be dropped in WEB-INF/lib and should be ready for use once the web container is restarted or this application is restarted. It should also allow you to package your view components as well in the jar.

In the next few posts I will try to show how such a simple yet effective system can be build by extending the Spring framework. I will also show some good practices that I learnt while building applications with this framework extension which I call WebPlug. The code and documentation will be available soon on Sourceforge. 

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