Question

public interface UserRepository extends JpaRepository<User, Long> {

  @Query(value = "SELECT * FROM USERS WHERE EMAIL_ADDRESS = ?0", nativeQuery = true)
  User findByEmailAddress(String emailAddress);
}

我们说我有上面的代码，我从用户那里选择*。如果我不希望此方法返回User对象，我该怎么办？有没有办法我可以手动将数据映射到自定义对象MyUser？我可以在UserRepository界面中完成所有这些吗？

谢谢！

Answer 1

你可以做这样的事情

@Query(value = "SELECT YOUR Column1, ColumnN FROM USERS WHERE EMAIL_ADDRESS = ?0", nativeQuery = true)
List<Object[]> findByEmailAddress(String emailAddress);

您必须进行映射。看一下Spring Data Repository。 Source

Answer 2

What about interface based projection？

基本上，您使用与SQL查询参数相对应的getter编写接口。

通过这种方式，您甚至不需要在投影上强制使用@Id参数：

public class Book {
     @Id
     private Long id;
     private String title;
     private LocalDate published;
}

public interface BookReportItem {
     int getYear();
     int getMonth();
     long getCount();
}

public interface BookRepository extends Repository<Book, Long> {
     @Query(value = "select " +
                    "  year(b.published) as year," +
                    "  month(b.published) as month," +
                    "  count(b) as count," +
                    " from Book b" +
                    " group by year(b.published), month(b.published)")
     List<BookReportItem> getPerMonthReport();
}

它使用下面的org.springframework.data.jpa.repository.query.AbstractJpaQuery$TupleConverter$TupleBackedMap作为当前Spring实现中接口的代理。

它也适用于nativeQuery = true。

SpringDataJPA：使用Native Query进行自定义数据映射

2 个答案: