Java Persistence Query Language
Java Persistence Query Language (JPQL) объектке бағытталған платформаға байланысы жоқ мәліметтер базасының тілі.
| Java Persistence Query Language | |
|---|---|
| Бұған ықпал етті | SQL |
| Операциялық жүйесі | Cross-platform |
Мысалдар
өңдеу@Entity
public class Publisher {
@Id
private Integer id;
private String name;
private String address;
@OneToMany(mappedBy = "publisher")
private List<Book> books;
}
Then a simple query to retrieve the list of all authors, ordered alphabetically, would be:
SELECT a FROM Author a ORDER BY a.firstName, a.lastName
To retrieve the list of authors that have ever been published by XYZ Press:
SELECT DISTINCT a FROM Author a INNER JOIN a.books b WHERE b.publisher.name = 'XYZ Press'
JPQL supports named parameters, which begin with the colon (:). We could write a function returning a list of authors with the given last name as follows:
import javax.persistence.EntityManager;
import javax.persistence.Query;
import org.apache.commons.lang.StringUtils;
...
@SuppressWarnings("unchecked")
public List<Author> getAuthorsByLastName(String lastName) {
String queryString = "SELECT a FROM Author a " +
"WHERE :lastName IS NULL OR LOWER(a.lastName) = :lastName";
Query query = getEntityManager().createQuery(queryString);
query.setParameter("lastName", StringUtils.lowerCase(lastName));
return query.getResultList();
}
Hibernate Query Language
өңдеуJPQL is based on the Hibernate Query Language (HQL), an earlier non-standard query language included in the Hibernate object-relational mapping library.
Hibernate and the HQL were created before the JPA specification. As of Hibernate 3 JPQL is a subset of HQL.