Question

无法从NamedQuery获取整数???

@NamedQuery(    name = Comm.COUNTLIKEVALUEINHOLDER,
        query = "SELECT COUNT(c.id) " +
            "FROM Comm c " +
            "JOIN c.element e " +
            "WHERE c.search1 LIKE :search1 " +
            "AND c.search2 = :search2 " +
            "AND c.type = :type " +
            "AND e.holderelement = :holder"
    )

Object q = em.createNamedQuery(Comm.COUNTLIKEVALUEINHOLDER)
    .setParameter("search1", "bla%")
    .setParameter("search2", "bla2")
    .setParameter("type", t)
    .setParameter("holder", h)
    .getSingleResult();

我从COUNT Aggregat返回实体，而不是Long或Integer。

但是我在这里得到一个整数。这是完全相同的查询。

Object i = em.createQuery("SELECT COUNT(c.id) " +
    "FROM Comm c " +
    "JOIN c.element e " +
    "WHERE c.search1 LIKE :search1 " +
    "AND c.search2 = :search2 " +
    "AND c.type = :type " +
    "AND e.holderelement = :holder")
    .setParameter("search1", "bla%")
    .setParameter("search2", "bla2")
    .setParameter("type", t)
    .setParameter("holder", h)
    .getSingleResult();

有人有想法吗？

Answer 1

简短回答：

em.createQuery用于创建动态查询。返回类型由QL语言的返回类型决定（上例中的“SELECT COUNT（c.id）”。）

em.createNamedQuery用于创建静态查询。返回类型可以是类型化的，例如：

Object q = em.createNamedQuery(Comm.COUNTLIKEVALUEINHOLDER)
   .setParameter("search1", "bla%")
   .setParameter("search2", "bla2")
   .setParameter("type", t)
   .setParameter("holder", h)
   .getSingleResult();

Integer count = (Integer) q;

` 另见：http://www.objectdb.com/java/jpa/query/api

JPA Eclipselink NamedQuery与查询COUNT

1 个答案: