The Digester package lets you configure an XML -> Java object mapping module,
which triggers certain actions called rules whenever a particular pattern of
nested XML elements is recognized. A rich set of predefined rules is available
for your use, or you can also create your own. Advanced features of Digester
include:

  - Ability to plug in your own pattern matching engine, if the standard one is
    not sufficient for your requirements.
  - Optional namespace-aware processing, so that you can define rules that are
    relevant only to a particular XML namespace.
  - Encapsulation of Rules into RuleSets that can be easily and conveniently
    reused in more than one application that requires the same type of
    processing