Limit number of results in JPQL

How it is possible to limit the number of results retrieved from开发者_JAVA技巧 a database?

select e from Entity e /* I need only 10 results for instance */

You can try like this giving 10 results to be fetched explicitly.

entityManager.createQuery(JPQL_QUERY)
             .setParameter(arg0, arg1)
             .setMaxResults(10)
             .getResultList();

It will automatically create native query in back-end to retrieve specific number of results, if the backend supports it, and otherwise do the limit in memory after getting all results.

You can set an offset too using setFirstResult()

em.createNamedQuery("Entity.list")
  .setFirstResult(startPosition)
  .setMaxResults(length);

If you are using Spring data JPA, then you can use Pageable/PageRequest to limit the record to 1 or any number you want. The first argument, is the page no, and the second argument is the number of records.

Pageable page = PageRequest.of(0, 1);
Entity e = entityRepository.findAll(page);

Make sure the entityRepostitory interface extends JpaRepository (which supports sorting and pagination).

Import

import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;

Repository

@Query(value = "select * from table");
public Page<Dto> limited(Pageable pageable);

Service

Page<Dto> returnValue= repo.limited(PageRequest.of(0, 1));
return returnValue.getContent();

just try with and without getContent();