JPA和原生查询

Question

我面临着与本地查询一个奇怪的事情：

如果我想使用一个名为原生查询像下面

@NamedNativeQuery(name = "native_count_avg_guest_quizzes", resultClass = java.math.BigDecimal.class, query = "select avg(c) as r from ((select count(*) as c from user_quiz uq join user u on (uq.user_id = u.id) where u.status = 'temporary' group by u.id) as res)") 

应用程序不能运行，我有

org.hibernate.HibernateException: Errors in named queries: native_count_avg_guest_quizzes_ 

但是，如果我不使用NamedNativeQuery和仅仅创建如下所示的动态本地查询相同的查询工作正常：

entityManager.createNativeQuery(
         "select avg(c) as r from ((select count(*) as c from user_quiz uq join user u on (uq.user_id = u.id) where u.status = 'temporary' group by u.id) as res)") 
         .getSingleResult() 

为什么？我在做什么错了NamedNativeQuery？由于

更新： 实体类如下

@Entity 
@Table(name = "user_quiz") 
@NamedNativeQueries({ 
    @NamedNativeQuery(name = "native_count_avg_guest_quizzes", resultClass = java.math.BigDecimal.class, query = "select avg(c) as r from ((select count(*) as c from user_quiz uq join user u on (uq.user_id = u.id) where u.status = 'temporary' group by u.id) as res)") 
}) 
@NamedQueries({ 
    @NamedQuery(name = "list_clients_quizzes", query = "select uq from UserQuiz uq where uq.quiz.client.id = :clientId"), 
    ....... 
}) 
public class UserQuiz extends Measurable { 
....... 
} 

Answer 1

createNativeQuery用于意味着DB能够理解并执行查询（例如，select * from some_table where id = '0001'）原生SQL查询语言;

它可能会导致数据库依赖。现在你用的是JPQL语言，这就是为什么用createQuery()或createNameQuery()用@NameQuery注释唱歌。

实施例：

@NameQuery

@NamedQuery(name = "findAllEmployee", query = "select e from Employee e") 
@Entity 
public class Employee { 
    @Id int id; 
    String name; 
    // ... 
} 

Query query = em.createNamedQuery("findAllEmployee"); 
query.getResultList() 

动态

Query query = em.createQuery("select e from Employee e"); 
    query.getResultList()? 

* 母语

Query query = em.createNativeQuery("SELECT * FROM EMPLOYEE_TBL"); 
query.getResultList()? 

Answer 2

从@NamedNativeQuery中删除resultClass。

见https://stackoverflow.com/a/9763489

对于NamedNativeQueries只能使用resultClass时，结果却映射到实体。