Jakarta Persistence Query Language

Example JPA Classes, getters and setters omitted for simplicity.

@Entity

public class Author {

@Id

private Integer id;

private String firstName;

private String lastName;

@ManyToMany

private List books;

}

@Entity

public class Book {

@Id

private Integer id;

private String title;

private String isbn;

@ManyToOne

private Publisher publisher;

@ManyToMany

private List authors;

}

@Entity

public class Publisher {

@Id

private Integer id;

private String name;

private String address;

@OneToMany(mappedBy = "publisher")

private List 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.TypedQuery;

...

public List getAuthorsByLastName(String lastName) {

String queryString = "SELECT a FROM Author a " +

"WHERE a.lastName IS NULL OR LOWER(a.lastName) = LOWER(:lastName)";

TypedQuery query = getEntityManager().createQuery(queryString, Author.class);

query.setParameter("lastName", lastName);

return query.getResultList();

}

JPQL 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.

{{Reflist}}

• {{citation

|last1 = Bauer

|first1 = Christian

|last2 = King

|first2 = Gavin

|last3 = Gregory

|first3 = Gary

| year = 2016

| title = Java Persistence with Hibernate

| edition = Second

| publisher = Manning Publications

| isbn = 978-1617290459

| url =

}}

• Object-relational mapping
• Hibernate (framework)
• Jakarta Persistence

• {{official website}}
• [https://eclipse-ee4j.github.io/jakartaee-tutorial/#full-query-language-syntax Full Query Language Syntax from The Jakarta EE 8 Tutorial]
• [https://www.objectdb.com/java/jpa/query JPA Queries and JPQL - a chapter of the ObjectDB Manual]
• [https://torpedoquery.org/ Type safe Hibernate (HQL) query engine - TorpedoQuery]

{{Jakarta Persistence}}

Category:Query languages

Category:Data modeling languages

Category:Java enterprise platform