JPQL

1 개요[ | ]

Java Persistence Query Language; JPQL
자바 퍼시스턴스 쿼리 언어

플랫폼에 독립적인 객체지향 쿼리 언어
자바 퍼시스턴스 API 스펙의 일부로서 정의됨
관계DB에 저장된 개체에 대한 쿼리 작성시 사용

2 예시[ | ]

@Entity
public class Author {
    @Id
    private Integer id;
    private String firstName;
    private String lastName;
 
    @ManyToMany
    private List<Book> books;
}
 
@Entity
public class Book {
    @Id
    private Integer id;
    private String title;
    private String isbn;
 
    @ManyToOne
    private Publisher publisher;
 
    @ManyToMany
    private List<Author> authors;
}
 
@Entity
public class Publisher {
    @Id
    private Integer id;
    private String name;
    private String address;
 
    @OneToMany(mappedBy = "publisher")
    private List<Book> books;
}

이름순 저자 목록

SELECT a FROM Author a ORDER BY a.firstName, a.lastName

출판사가 "XYZ 프레스"를 통해 책을 낸 저자 목록

SELECT DISTINCT a FROM Author a INNER JOIN a.books b WHERE b.publisher.name = 'XYZ Press'

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 a.lastName IS NULL OR LOWER(a.lastName) = :lastName";
    Query query = getEntityManager().createQuery(queryString);
    
    query.setParameter("lastName", StringUtils.lowerCase(lastName));
    return query.getResultList();
}

3 같이 보기[ | ]

4 참고[ | ]

https://en.wikipedia.org/wiki/Java_Persistence_Query_Language