Convenient superclass for application objects that want to be aware of
the application context, e.g. for custom lookup of collaborating beans
or for context-specific resource access. It saves the application
context reference and provides an initialization callback method.
Furthermore, it offers numerous convenience methods for message lookup.
There is no requirement to subclass this class: It just makes things
a little easier if you need access to the context, e.g. for access to
file resources or to the message source. Note that many application
objects do not need to be aware of the application context at all,
as they can receive collaborating beans via bean references.
Many framework classes are derived from this class, particularly
within the web support.