Going Inside Velocity

Abstract

In this chapter I’ll depart a bit from the discussion on how to use Velocity in your applications and how you can leverage tools built on Velocity as part of your development process. Instead, I’ll take advantage of the fact that Velocity is open source and discuss the internals of Velocity. So far, you’ve seen plenty of examples of how you use Velocity in your application, but as yet I haven’t discussed what happens inside the Velocity runtime to create the output for your code. If you plan to use Velocity to build even moderately sized systems, an understanding of its inner workings will help immensely when you need to step off the beaten path or when things don’t quite work as you had imagined. More specifically, in this chapter I’ll discuss the following:

• A typical processing cycle

• The Velocity startup process

• The ResourceManager subsystem

• The Velocity template parser

• The Introspection implementation