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.
Considering we have the following entities: And, you want to fetch some parent Post entities along with all the associated comments and tags collections. If you are using more than one JOIN FETCH directives: List<Post> posts = entityManager.createQuery(“”” select p from Post p left join fetch p.comments left join fetch p.tags where p.id between :minId … Read more
I don’t believe you’ll be able to do that with the method name approach to query definition. From the documentation (reference): Although getting a query derived from the method name is quite convenient, one might face the situation in which either the method name parser does not support the keyword one wants to use or … Read more
according to the book “Pro EJB 3 Java Persistence API” Constructor Expressions A more powerful form of SELECT clause involving multiple expressions is the constructor expression, which specifies that the results of the query are to be stored using a user-specified object type. Consider the following query: SELECT NEW example.EmployeeDetails(e.name, e.salary, e.department.name) FROM Employee e … Read more
If you do LIKE :code and then do namedQuery.setParameter(“code”, “%” + this.value + “%”); Then value remains free from the ‘%’ sign. If you need to use it somewhere else in the same query simply use another parameter name other than ‘code’ .
I’m not sure for JPA 1.0 but you can pass a Collection in JPA 2.0: String qlString = “select item from Item item where item.name IN :names”; Query q = em.createQuery(qlString, Item.class); List<String> names = Arrays.asList(“foo”, “bar”); q.setParameter(“names”, names); List<Item> actual = q.getResultList(); assertNotNull(actual); assertEquals(2, actual.size()); Tested with EclipseLInk. With Hibernate 3.5.1, you’ll need to … Read more
You can achieve complex queries with specifications by JpaSpecificationExecutor in spring data. Repository interface must extend the JpaSpecificationExecutor<T> interface so we can specify the conditions of our database queries by creating new Specification<T> objects. The trick is in the use of the Specification interface in combination with a JpaSpecificationExecutor. here is the example: @Entity @Table(name … Read more
When using IN with a collection-valued parameter you don’t need (…): @NamedQuery(name = “EventLog.viewDatesInclude”, query = “SELECT el FROM EventLog el WHERE el.timeMark >= :dateFrom AND ” + “el.timeMark <= :dateTo AND ” + “el.name IN :inclList”)
Don’t avoid it, the SELECT NEW is there because there are perfectly valid use cases for it as reminded in the ยง10.2.7.2. JPQL Constructor Expressions in the SELECT Clause of the EJB 3.0 JPA Specification: A constructor may be used in the SELECT list to return one or more Java instances. The specified class is … Read more