Our application exposes queries by way of web services, and what we’ve found is that our clients often want custom queries, either by way of further limiting the results returned by specifying additional criteria, or by asking for things that we don’t already expose.
Now, we can take the approach of creating new methods for each of these new methods, but that’s somewhat inconvenient; deployment of our application at a client site usually requires weeks of staged integration testing. We’ve proposed a named query mechanism, where the application administrator would define queries by name that are parameterized, and a corresponding web service that simply invokes these parameters. However, I can’t help but think that someone has solved this problem before, so I’d like some input from the SO community on possible designs.
Thanks!
Updates
The specification pattern is a good one, but our application deals with enough data that we want to push as much of the querying work down into an RDBMS, which can do a better job of optimizing the query plan than we would ever want to. Moreover, we support three RDBMS backends, so we’re stuck using a greatest-common-denominator approach: we use as much capability as the least functional database can provide.
I would also recommend to consider the ‘Specification Pattern’ in this type of applications as a design decision for your backend. Check the following posts about ‘Specification Pattern’:
http://www.mattberther.com/2005/03/25/the-specification-pattern-a-primer/
http://devlicio.us/blogs/jeff_perrin/archive/2006/12/13/the-specification-pattern.aspx