This class encapsulates the String that is used to identify the
subject that a listener is interested in. Using plain Strings causes several severe problems:
- it's easy to misspell a subject, leading to undesired behaviour at runtime that is hard to debug.
- in systems with many different subjects there is no safeguard for defining the same subject twice for different purposes. This is especially true in a distributed setting.
@author Dirk Olmes
@author Holger Hoffstaette