querybycriteria

Querybycriteria, or query by criteria, is a pattern and approach used in data access layers to construct queries by specifying filtering criteria rather than writing explicit query strings. It is commonly employed in database access frameworks, Object-Relational Mappers (ORMs), and search APIs to build dynamic, type-safe, or declarative queries from user input or programmatic rules.

The core idea is to express what data should be retrieved through a collection of criteria, such as field names, values, operators, and logical combinations. Typical criteria components include equals, not equals, greater than, less than, in, like, and existence checks, often combined with and/or logic. Implementations may accept criteria as simple key-value maps, dedicated criterion objects, or via a fluent builder that supports chaining and nesting.

Query by criteria enables dynamic query composition, reusable query fragments, and safer query construction through parameterization, reducing the risk of injection and syntax errors. It is frequently paired with features like sorting and pagination to support common search and listing use cases. Depending on the framework, the criteria are translated into the underlying query language—SQL for relational databases, JSON-based queries for document stores, or DSLs for search engines.

Common patterns related to this approach include the Criteria API and the Specification pattern, which promote type-safety and composability. Notable implementations appear in JPA/Hibernate, Spring Data (Query by Example and Specification), and various NoSQL and search libraries. See also: query by example, criteria API, and specification pattern.