java - 从 Spring Data 中的多个表中进行选择

Question

我需要编写一个选择查询，从 Spring Data Repository 层的多个表中获取数据。我知道我们可以使用 @Query 编写自定义查询，但它只从单个表返回值？

SELECT s.service_id, s.name, us.rating_id 
FROM services s, 
     ratings r, 
     user_services us
where 
    us.service_id = s.service_id and
    us.rating_id = r.rating_id and
    us.user_id= ?;

Answer 1

您的接口(interface)方法可以使用 native SQL 从多个表中选择列，该方法将返回一个对象数组列表:

public interface MyRepository extends JpaRepository {
  @Query(name = [name], nativeQuery = true)
  List<Object[]> methodThatQueriesMultipleTables();
}

列表中的每一项都是Object数组，即一行数据

您还可以创建自定义存储库实现:

How to add custom method to Spring Data JPA

@NoRepositoryBean
public interface CustomRepository<[Your object]> {
    List<Object[]> methodThatQueriesMultipleTables();
}

public class MyRepositoryImpl<[Your object]> implements CustomRepository<[Your object] {
    @PersistenceContext
    private EntityManager entityManager;

    @Override
    public List<Object[]> methodThatQueriesMultipleTables() {
        //use JPA query to select columns from different tables
        Query nativeQuery = entityManager.createNativeQuery("query");
        return query.getResultList();
    }
}