Question

家伙！我有两个类关于ManyToMany

的两个属性

public class ExhibitorList {

@ManyToMany(fetch=FetchType.EAGER)
@JoinTable(name="exhibitor_layouts",
    joinColumns=@JoinColumn(name="exhibitor_list_id"),
    inverseJoinColumns=@JoinColumn(name="layout_id"))
private List<Layout> layouts = new ArrayList<>();

}

并且

public class Layout {

@ManyToMany(mappedBy="layouts",fetch=FetchType.EAGER)
private List<ExhibitorList> exhibitor = new ArrayList<>();

}

我正在使用HPQ来获取实体。

final String FIND_ALL_JOIN = "SELECT ex from ExhibitorList as ex LEFT join FETCH ex.layouts order by ex.id";

@Query(FIND_ALL_JOIN)
List<ExhibitorList> findAllJoin();

问题是这个查询得到任何有布局的参展商的子选择（目前我有6个参展商有布局。

Hibernate: select exhibitorl0_.id as id1_6_0_, layout2_.id as id1_8_1_, exhibitorl0_.catalogue_number as catalogu2_6_0_, exhibitorl0_.exhibitor_name as exhibito3_6_0_, exhibitorl0_.exhibitor_price as exhibito4_6_0_, exhibitorl0_.oracle_number as oracle_n5_6_0_, layout2_.created as created2_8_1_, layout2_.name as name3_8_1_, layout2_.status as status4_8_1_, layouts1_.exhibitor_list_id as exhibito1_5_0__, layouts1_.layout_id as layout_i2_5_0__ from exhibitor_list exhibitorl0_ left outer join exhibitor_layouts layouts1_ on exhibitorl0_.id=layouts1_.exhibitor_list_id left outer join layout layout2_ on layouts1_.layout_id=layout2_.id order by exhibitorl0_.id
Hibernate: select exhibitor0_.layout_id as layout_i2_5_0_, exhibitor0_.exhibitor_list_id as exhibito1_5_0_, exhibitorl1_.id as id1_6_1_, exhibitorl1_.catalogue_number as catalogu2_6_1_, exhibitorl1_.exhibitor_name as exhibito3_6_1_, exhibitorl1_.exhibitor_price as exhibito4_6_1_, exhibitorl1_.oracle_number as oracle_n5_6_1_ from exhibitor_layouts exhibitor0_ inner join exhibitor_list exhibitorl1_ on exhibitor0_.exhibitor_list_id=exhibitorl1_.id where exhibitor0_.layout_id=?
Hibernate: select exhibitor0_.layout_id as layout_i2_5_0_, exhibitor0_.exhibitor_list_id as exhibito1_5_0_, exhibitorl1_.id as id1_6_1_, exhibitorl1_.catalogue_number as catalogu2_6_1_, exhibitorl1_.exhibitor_name as exhibito3_6_1_, exhibitorl1_.exhibitor_price as exhibito4_6_1_, exhibitorl1_.oracle_number as oracle_n5_6_1_ from exhibitor_layouts exhibitor0_ inner join exhibitor_list exhibitorl1_ on exhibitor0_.exhibitor_list_id=exhibitorl1_.id where exhibitor0_.layout_id=?
Hibernate: select exhibitor0_.layout_id as layout_i2_5_0_, exhibitor0_.exhibitor_list_id as exhibito1_5_0_, exhibitorl1_.id as id1_6_1_, exhibitorl1_.catalogue_number as catalogu2_6_1_, exhibitorl1_.exhibitor_name as exhibito3_6_1_, exhibitorl1_.exhibitor_price as exhibito4_6_1_, exhibitorl1_.oracle_number as oracle_n5_6_1_ from exhibitor_layouts exhibitor0_ inner join exhibitor_list exhibitorl1_ on exhibitor0_.exhibitor_list_id=exhibitorl1_.id where exhibitor0_.layout_id=?
Hibernate: select exhibitor0_.layout_id as layout_i2_5_0_, exhibitor0_.exhibitor_list_id as exhibito1_5_0_, exhibitorl1_.id as id1_6_1_, exhibitorl1_.catalogue_number as catalogu2_6_1_, exhibitorl1_.exhibitor_name as exhibito3_6_1_, exhibitorl1_.exhibitor_price as exhibito4_6_1_, exhibitorl1_.oracle_number as oracle_n5_6_1_ from exhibitor_layouts exhibitor0_ inner join exhibitor_list exhibitorl1_ on exhibitor0_.exhibitor_list_id=exhibitorl1_.id where exhibitor0_.layout_id=?
Hibernate: select exhibitor0_.layout_id as layout_i2_5_0_, exhibitor0_.exhibitor_list_id as exhibito1_5_0_, exhibitorl1_.id as id1_6_1_, exhibitorl1_.catalogue_number as catalogu2_6_1_, exhibitorl1_.exhibitor_name as exhibito3_6_1_, exhibitorl1_.exhibitor_price as exhibito4_6_1_, exhibitorl1_.oracle_number as oracle_n5_6_1_ from exhibitor_layouts exhibitor0_ inner join exhibitor_list exhibitorl1_ on exhibitor0_.exhibitor_list_id=exhibitorl1_.id where exhibitor0_.layout_id=?

如果我使用findAll（）计划Spring Data;例如，我得到N + 1问题。

如何通过一个选择

为所有参展商提供布局

Answer 1

尝试：

 select ex from ExhibitorList ex order by ex.id

您不需要加入布局。你有很多关系。

使用查询的示例：

Query q = getSession().createQuery("select ex from ExhibitorList ex order by ex.id" ); 

return (List<ExhibitorList>) q.list();

休眠 - ManyToMany子选择甚至LEFT JOIN FETCH

1 个答案: