|
Definition of an interface for evaluating keys for hierarchical
configurations.
An expression engine knows how to map a key for a configuration's
property to a single or a set of configuration nodes. Thus it defines the way
how properties are addressed in this configuration. Methods of a
configuration that have to handle property key (e.g.
getProperty() or addProperty() do not interpret
the passed in keys on their own, but delegate this task to an associated
expression engine. This expression engine will then find out, which
configuration nodes are addressed by the key.
Seperating the task of evaluating property keys from the configuration object
has the advantage that many different expression languages (i.e. ways for
querying or setting properties) can be supported. Just set a suitable
implementation of this interface as the configuration's expression engine,
and you can use the syntax provided by this implementation.
since:
1.3
author:
Oliver Heger |