mysql - 带连接的 spring data jpa native 查询

Question

如何在 spring data jpa 中执行原生查询，同时获取子实体？如果我在子实体对象上有 Eager FetchType，则 spring 数据正在执行 2 个查询。 1 个用于父实体，1 个用于子实体。

有没有办法只执行 1 个 native 查询来获取父实体和子实体？

parent :

@Entity
public class Parent {
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private long id;

   @Temporal(TemporalType.TIMESTAMP)
   private Date ts;

   @ManyToOne(fetch=FetchType.LAZY)
   private Child child;
}

child :

@Entity
public class Child {
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private long id;

   @OneToMany(fetch=FetchType.LAZY, mappedBy="parent")
   private Parent parent;
}

查询:

public interface ParentRepository extends Repository<Parent, Integer> {
    @Query(value = "SELECT * from parents p inner join children c on c.id=p.childId where TIMESTAMPDIFF(SECOND, p.ts, CURRENT_TIMESTAMP) < :interval", nativeQuery = true)
    Parent findOneByInterval(@Param("interval") long interval);
}

我正在使用 Hibernate 5、MySQL 以及 Spring Data JPA。

我还尝试将 @NamedEntityGraph 添加到父类，将 @EntityGraph 添加到查询方法，但没有成功。

Answer 1

如果你想要父对象，你可以这样尝试

public interface ParentRepository extends Repository<Parent, Integer> {

    @Query(value = "SELECT p.* from parents p inner join children c on c.id=p.childId where TIMESTAMPDIFF(SECOND, p.ts, CURRENT_TIMESTAMP) < :interval", nativeQuery = true)
    Parent findOneByInterval(@Param("interval") long interval);
}

(或) Spring data JPA 将为原生 Query 返回对象数组 所以，

public interface ParentRepository extends Repository<Parent, Integer> {

    @Query(value = "SELECT * from parents p inner join children c on c.id=p.childId where TIMESTAMPDIFF(SECOND, p.ts, CURRENT_TIMESTAMP) < :interval", nativeQuery = true)
    List<Object[]> findOneByInterval(@Param("interval") long interval);
}