Query Object Pattern


Definition
A Query Object is an interpreter, that is, a structure of objects that can form itself into a SQL query (martin fowler).

Applicability
  • When there is a need to avoid to know what the database schema looks like to form queries.

Consequences
  • Hides the SQL inside parameterized methods.
  • Those who write the queries can do so independently of the database schema and changes to the schema can be localized in a single place.

Downsides
  • Makes it difficult to form more ad hoc queries.

Sample Code

Comments

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  3. This is what exactly the specification pattern does as well.

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