Recently, SpringSource released the first version of their DM server. The SpringSource DM Server provides the ability to build enterprise web applications. In the basis, S2DM is a fine mixture of Equinox and Tomcat.
Building OSGi-based web applications was already possible, but it is tedious and error prone work. The typical hello-world example was easy to get going, but as soon as Hibernate or any other framework that helps in larger applications show up, so do your good old class loading problems. For classes to be visible in OSGi, a bundle must declare an Import-Package entry in the Manifest file. Chances are small that Hibernate (even if it were packaged as an OSGi bundle) has these entries for your persistent classes. This is where S2DM server comes in. It allows the more-than-hello-world web applications to be deployed in an environment where you can benefit from the best of OSGi, without the class loading misery. To do this, they have included some extra Manifest entries that are translated to OSGi-compliant directives at load time.
Comparable to the WAR, or better, EAR file, S2DM server supports the PAR file. A PAR file is much like a Jar, with some special headers in the Manifest file, containing all your bundle jars. Some of these jars may contain web bundles, while other typically contain domain classes or the service layer implementation. Contrary to EAR files, a PAR should only contain your own code. It is best practice to deploy frameworks and third party libraries separately. I’ll explain why later on.
With enterprise applications come enterprise development processes, using continuous integration, build servers and maven. In this post, I’ll lay out what you need to get maven to build S2DM server compliant bundles, and better, PAR files.
Continue reading Building Spring DM server compliant OSGi bundles with Maven
