DDD and configuration

Question

How do I give access to user configured settings in DDD?

We have a configuration database which stores items as a bunch of key-value pairs. This doesn't really seem to fit the repository pattern, so how do I enable the user to access these configuration values?

Ideally I'd like to have separate classes for different groupings of configuration, ie.. BillingSettings, ReportSettings, TaxSettings.

It would seem odd to provide a separate repository for each of these, but I also want to maintain persistence ignorance for these settings classes.

What is the correct way of enabling access to configuration in DDD?

Answer 1

What I typically do is just abstract the configuration using interfaces, e.g. IBillingConfiguration, IReportConfiguration, etc. The implementations of these are then what get passed into the relevant methods (or injected into the relevant objects).

Where the values comes from then really shouldn't matter. There are times when I do use a repository when storing the values in a database and then I'd have something like IConfigurationPropertyRepository. It is somewhat of an awkward fit since a ConfiruationProperty does not quite feel like a first-class citizen in the Entity world but it does seem to get the job done.

I would return some implementation of a IBillingConfiguration that just gets the required property from an underlying collection or ConfigurationProperty objects.

The relevant Get and Save methods for each I{Some}Configuration would be implemented on the ConfigurationPropertyRepository so that I only get/save that subset of the properties that need to be applied.