Applying UML and Patterns: An Introduction to Object-Oriented Analysis and Design and the Unified Process, Second Edition

34.15. Consolidating and Hiding SQL Statements in One Class

Hard-coding SQL statements into different RDB mapper classes is not a terrible sin, but it can be improved upon. Suppose instead:

• There is a single Pure Fabrication class (and it's a singleton) RDBOperations where all SQL operations (SELECT, INSERT, ...) are consolidated.

• The RDB mapper classes collaborate with it to obtain a DB record or record set (for example, ResultSet).

• Its interface looks something like this:

  								class RDBOperations
  								{
  								public ResultSet getProductSpecificationData( OID oid ) {...}
  								public ResultSet getSaleData( OID oid ) {...}
  								...
  								}
  							

So that, for example, a mapper has code like this:

						class ProductSpecificationRDBMapper extends AbstractPersistenceMapper
						{
						protected Object ...