java - JPQL 查询子页面和孙子的连接获取会抛出异常查询指定的连接获取

Question

我有实体:

class Parent {
  ...
  @OneToMany(Fetch = FetchType.EAGER)
  @OrderBy("id")
  private List<Child>  children;
}


class Child{
  ...
  @OneToMany(Fetch = FetchType.LAZY)
  @OrderBy("id")
  private List<GrandChild> grandChildren;
}

class GrandChild {
  ...
}

我想查询分页的子项并获取孙子项。我还按名字过滤 child ，但我认为这并不重要。我有这样的 JPQL 查询:

@Query("select c " +
       "from Parent p " +
       "inner join p.children c " +
       "inner join fetch c.grandchildren g " +
       "where p = :parent and " +
       "c.childName like concat(:childName,'%')")
    Page<Expense> findBy(@Param("parent") Parent parent, @Param("childName")String childName, Pageable pageable);

在启动 Spring Boot 应用程序期间抛出异常:

query specified join fetching, but the owner of the fetched association was not present in the select list

消息很简单，但是我无法将父级添加到选择语句，因为我只想要子级。

Answer 1

c.grandchildren 缺少别名 e

@Query("select e " +
       "from Parent p " +
       "inner join p.children c " +
       "inner join fetch c.grandchildren e" +
       "where p = :parent and " +
       "c.childName like concat(:childName,'%')")
    Page<Expense> findBy(@Param("parent") Parent parent, @Param("childName")String childName, Pageable pageable);