GlassFish is one of the leading open source application server. Sun claim to have more than 14 million downloads of the server. But I wonder how many are used in production environment and not by students and developers (I have a regirstered version of Gfv2 on my laptop)?
The new version of server was redegined from top to bottom to run on the popular modular runtime called OSGi runtime. Glassfish makes use of Apache Felix, an open source OSGi runtime from Apache. Sun claims that, the application server can also run on Eclipse's Equinox runtime. The server brings in lots of changes in how an application sever works. The server startup time is drastically reduced compared to the pervious version. This was acheived by the way how classes are loaded in the server. At startup a full fledged application server do not start, instead only the necessary modules (containers) get loaded.Containers do not get loaded unless they have a component to execute. For example, EJB container do not start untill I have a EJB depoyed.
The server comes with a full web container that can host servlets 2.5, JSP and JSF. JSF 2.0 is provided as preview. Developers can also have a first look at EJB 3.1. They can also make use of the JPA for persistence. Sun introduces the concept of a update center from which you can download other modules like web service stack or Jersey . The server also introduces containers that support native jRuby/Rails, Groovy/Grails.
The major advantage for a development team from GlassFish is that it provides the ability to maintain the sessions active even during deployment. This feature helps both developers and testers to test the code, refine them if need and test it rather than going through the long cycle that we currently go through. So next time you find a bug when testing your code, all you need to do is change your logic, deploy and start testing with the same session. Netbeans 6.5 is said to have good integration with the new server, providing deployment of new code on the server as and when you save the code and its compliation error free! Other advantages includes the availability of easy to use admin and cofiguration tool and server being available for all major platforms.
Now we have SpringSource,IBM and Sun implementing application servers on OSGi technology, are we seeing the tsunami of OSGi support and implementation? Even thought these changes do not provide a visible change to the end users, JEE seems to be adopting OSGi technology at a large scale. I am sure Oracle will come up with an implementation using their (orginally BEA's) mSA technology, which is based on OSGi.
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