Maybe you are already convinced, but need some help convincing your colleagues that Avalon is right for you. Maybe you need some convincing yourself. Either way, this chapter will help wrap everything up, and provide you with some convincing arguments. We all need to fight Fear, Uncertainty, and Doubt (FUD) with the Open Source model. For arguments on the validity of Open Source, I will direct you to Eric S. Raymond's excellent treaties on the subject. Regardless of your opinions on his politics, the papers he wrote and compiled into the book The Cathedral and the Bazaar will give you the information you need to be convinced about the open source model as a whole.
The bottom line is that Avalon accomplishes the goal it was originally designed to fulfill. Avalon does not introduce new concepts and ideas, but rather uses and formalizes several concepts that have stood the test of time. The newest concept that influenced the design of Avalon is the Separation of Concerns pattern introduced sometime around 1995. Even then, Separation of Concerns is a formalization of System Analysis techniques.
Avalon's user base is measured in the hundreds. Several projects like Apache Cocoon, Apache JAMES, and Jesktop are all built on Avalon. Developers for those projects are users of Avalon Framework. Because of the number of users Avalon has, it is very well tested.
The authors of Avalon recognize that we are not the sole experts on server side programming. We use concepts and ideas from other people's research. We respond to feedback from our users. Avalon is not just designed by the five developers mentioned in the introduction -- the people who came up with the concepts of Inversion of Control, Separation of Concerns, and Component Oriented Programming designed it.
The beauty of Open Source projects is that the result is an amalgamation of the best ideas and the best code. Avalon has gone through periods of testing ideas and rejecting them because there was a better solution. You can take the knowledge gained by the Avalon team and use it in your own systems. You can take the predefined components in Excalibur and use them in your own projects -- they have been tested to work under heavy load without errors.
The Apache Software License (ASL) is compatible with just about every other license known. The biggest known exceptions are the GNU Public License (GPL) and the Lesser GNU Public License (LGPL). The important thing is that the ASL is friendly to corporate development, and does not force you to release your source code if you don't want to. It is the same license used for the Apache Software Foundation's venerable HTTP server.
Most of Avalon's users contribute back to the project in some way. This spreads the cost of developing, debugging, and documenting the framework across several users. It also means that Avalon's code has gone through a more extensive peer review than would ever be possible in one company. In addition, users of Avalon support Avalon. While it is true open source projects do not typically have a help desk or telephone support line, we do have a mailing list. Many times your questions can be answered in less time on the list than it would take on some support lines.
Developing on Avalon helps the developer to get into a mindset. That mindset focuses the efforts on how to identify Services, followed by an implementation of such service, a component. Since many of the details regarding the life of the components and Services in the system are already analyzed and designed, the developer only has to choose which ones they need.
It is important to state that Avalon development does not replace traditional Object Oriented Analysis and Design, but enhances it. You are still using the same techniques you did before, only now you have a tool set you can use to achieve your design faster.
Avalon Framework, Avalon Merlin, Avalon Repository and Avalon Logging are ready for you to use now. They are mature, powerful products and they are only getting better, by the day!
