CriteriaBuilder

CriteriaBuilder is a Java interface used as part of the Java Persistence API (JPA) to programmatically construct database queries. It allows developers to create complex queries in a type-safe manner, avoiding the potential errors associated with string-based SQL construction. The CriteriaBuilder acts as a factory for creating query elements such as predicates, expressions, and order specifications.

To use CriteriaBuilder, one typically obtains an instance from an EntityManager. Developers then use methods provided by the CriteriaBuilder to define various parts of a query. For instance, methods like 'equal', 'like', 'greaterThan', and 'in' are used to build predicate clauses that define the selection criteria. Expressions can be created to represent fields, literal values, or results of mathematical operations. Ordering is specified using the 'asc' and 'desc' methods.

The CriteriaBuilder is a key component in building dynamic queries where query logic might change based on user input or application state. It integrates with the Criteria API, which also includes interfaces like CriteriaQuery and Root, to define the overall structure of the query, the entities involved, and the desired results. By leveraging CriteriaBuilder, developers can create more robust and maintainable data access layers in their Java applications.