I have been a big fan of the Spring Framework since its first release in 2004 and have been using it in almost all my projects. When the application server written by the same company—the SpringSource dm Server—first came out in April 2008, even though it was in the beta release, I immediately installed it on my machine and tried it out. Note that when it was in the beta release, the dm Server was named the SpringSource Application Platform. When it came to the final release, the name was changed to the SpringSource dm Server, and the SpringSource Application Platform’s scope was extended to include a set of SpringSource tools, frameworks, and servers, which includes the dm Server as a core component. When I was trying out the dm Server, I could see already that it was to bring an evolution to enterprise Java application development. The dm Server is built on top of OSGi, a technology specially designed for building dynamic and modular systems in Java. OSGi brings many benefits to Java developers: first, it allows you to divide a system into multiple modules, each of which can be installed, uninstalled, updated, started, and stopped independently; second, it allows different versions of a module to be deployed at the same time so that different applications can choose a version to import at runtime.