Queries are represented in JPA by the
The JPA Query API section (in chapter 4 of the ObjectDB manual) provides detailed explanation of how exactly to use these interfaces to build and run JPQL queries.
TypedQuery interface (or alternatively the older
Query interface) is the only neccessary interface for defining and running string based JPQL queries (e.g.
"SELECT c FROM Country").
Criteria Query API
Building dynamic queries with a structure that is known only at runtime (e.g. depending on which fields are filled by a user in a form) can be done by concatenating JPQL strings into a valid complete JPQL query. JPA 2 introduced the JPA Criteria Query API, as a cleaner alternative that enables building a dynamic query by using instances of special types, representing query elements. Running criteria queries, however, still requires a
TypedQuery or a
Building a dynamic query using the criteria API is managed by the
As noted above, eventually every criteria query is managed by an ordinary
TypedQuery instance. The
CriteriaQuery instance merely represents the query during its building, and is equivalent to a JPQL query string (i.e. to a
String instance containing JPQL).
An essential interface for using the criteria API is the
CriteriaBuilder instance is the factory of criteria queries as well as of criteria query elements. It can be obtained either by the
getCriteriaBuilder method or by the
getCriteriaBuilder method (both methods are equivalent).
Criteria Query Elements
Criteria query elements are organized in this reference into three groups.
SELECT and ORDER BY elements (including tuples):
FROM clause elements (representing range variables, join and fetch):
Other criteria query expressions (for all the query clauses):