I have now been working on WLEvS for about 8 months. Before that time I was heavily involved with the development of Spring-OSGi and making sure that it met the needs of WLEvS.
Why the interest in Spring? What has BEA to gain by so extensively using an Open Source technology in one of its products? Well the answer is actually pretty easy. Event Driven Architectures (EDA) are now reaching the mainstream both in terms of interest and in terms of development. They are a key part of Gartner's Extreme Transaction Processing (XTP) vision for the future - a vision in which BEA is currently in pole position. But enough of the marketing, developers want to know what it means for them in terms of their day-to-day jobs. At a development level EDA is significantly different to things like Java EE and thus requires new programming paradigms and environments. So building event driven applications requires something other than Java EE, but Java EE has a key advantage - its a standard and everyone is familiar with it. Love it or hate it is pretty easy to find developers with Java EE experience. But what happens when you need to do something new? Proprietary APIs are no good - all customers are wary of "vendor lock-in", and developers especially so. The answer is pretty simple - use something that developers are already familiar with. Hence, in a word, Spring.
BEA has a pretty long and positive history with Spring, as evidenced on our Spring resource page. But more than just providing a familiar programming environment, Spring provides a powerful extension mechanism for event server developers and a user friendly way of accessing OSGI services via Spring-OSGI. Furthermore we have used Spring 2.x's extension mechanism to implement WLEvS' domain specific language for network assembly. The nice thing about this is that if you don't know Spring you don't have to use it, but if you want to go deeper you still can.
The simple things are easy and the difficult things are possible, or as the Spring folks are fond of saying, "simple and powerful."
