Recently I did some experiments in the base package of the
configuration2 branch (the new package was used mainly to keep the code
separated from the other classes). I would like to share the results
with others and get some feedback.
A new Configuration interface was created which includes methods from
the original Configuration interface, from AbstractConfiguration, and
from HierarchicalConfiguration. The goal is to provide a rich API for
dealing with all kinds of - especially hierarchical - configuration
settings.
With ConfigurationImpl there is a default implementation of the
Configuration interface. Note that this is not an abstract class, but a
fully functional implementation of all interface methods. This could be
achieved by separating the logic for actually accessing configuration
data into a new concept: a configuration source.
The basic idea is that a configuration source provides low-level access
methods for "raw" configuration properties. ConfigurationImpl can build
more powerful operations on top of a configuration source. One advantage
of this concept is a better separation of concerns, which has some
consequences:
- To implement access to a new configuration source a developer does not
have to extend a full-blown configuration class any more, but can focus
on the much leaner ConfigurationSource interface.
- A Configuration is now more a view of a configuration source providing
a richer API on top of it. Because the source holds the actual data it
is sufficient to move this object to all interested parties rather than
the Configuration with all its helper objects. Maybe a solution for our
serialization problem?
- For low-level manipulations of configuration settings the source can
be accessed directly. Features like loading and saving data would also
reside in the source. Maybe the proposed flush() and sync() operations
can be added here?
Currently, there are two kinds of configuration sources with a different
API: ConfigurationSource which provides a "flat" view on its properties,
and HierarchicalConfigurationSource which organizes its data in a
tree-like structure. ConfigurationImpl uses the latter for implementing
truly hierarchical operations. There is an adapter class for
transforming a flat configuration source into a hierarchical one.
This is more or less the current status. WDYT?
Oliver
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