SpringSource have released the GA version of the dm Server. The dm Server is an OSGi-based Java EE application server.
OSGi will allow you to keep the structure of your application even at runtime. You will be able to kiss good-bye to the monolithic deployment archives that obliterate your application’s structure. However, straight OSGi comes with a terrible price.
; set PE bit mov eax, cr0 or eax, 1 mov cr0, eax jmp cs:@pm @pm:
This switched the 80286 CPU to protected mode; the 80386 also brought paging and virtual address space. In protected mode, we can run the same code as in real mode, but the memory addresses are completely different. This means that old trusty code in BIOS is unusable; we can keep our applications, but the applications cannot use
int 0x13to read from the disk. We had to start using real operating systems, whose kernels process the applications’ requests and access the hardware directly, without the real-mode code in BIOS.
What does that have anything to do with OSGi? Well, OSGi can run any ol’ Java code, but you cannot “just add this jar to the classpath”. This means that virtually all applications need to be re-packaged and updated to make them run in OSGi execution environment. In fact, there is no application in OSGi, there are only bundles. This is in principle excellent, but we still think about applications as umbrellas for bundles.
SpringSource OSGi repository
The work involved in turning 100 odd jars in a typical Java EE application into OSGi bundles is terrible. Luckily, SpringSource have a repository of trusty old Java EE libraries turned into OSGi bundles. You can download and use these bundles in place of the jars you had in your JEE applications.
As you can guess, the dm Server bridges the pure OSGi world and standard Java EE application server world. You can deploy existing WAR as well as new PAR (Platform Archive, a collection of bundles). Additionally, each bundle can specify its personality. The personality specifies the type of code the bundle contains. A web personality tells the dm Server that the bundle will be processing HTTP requests and that it will need to be deployed in Tomcat, which is bundled with the dm Server.
We won’t go into detailed description of the dm Server’s architecture — we can’t give out all details of our book, SpringSource Application Platform in Action. We will, however, invite you to Spring in Finance Exchange, where Aleksa and I are going to show how to move a complex Java EE web application from WebLogic to the dm Server live!