Hibernate 是否可以统一由spring数据生成的findby查询

我有这样一个实体类：

@Entity
@Table(name="app_user_role")
public class AppUserRole implements Serializable {

    private static final long serialVersionUID = 1L;

    @EmbeddedId
    private AppUserRolePK id;

    //uni-directional many-to-one association to App
    @ManyToOne
    @JoinColumn(name="id_app", insertable=false, updatable=false)
    private App app;

    //uni-directional many-to-one association to Role
    @ManyToOne
    @JoinColumn(name="id_role", insertable=false, updatable=false)
    private Role role;

    //uni-directional many-to-one association to User
    @ManyToOne
    @JoinColumn(name="id_user", insertable=false, updatable=false)
    private User user;

}

然后，调用下一个方法：

List<AppUserRole> appUserRoles= appUserRoleRepository.findByAppAndUser(app, user);

它生成了多个分开的查询， 如何仅在一个查询中统一此查询

假设下一个方法仅生成一个查询：

AppUserRolePK appUserRolePK = new AppUserRolePK(app.getId(), role.getId(), user.getId() );
AppUserRole appUserRole1 = appUserRoleRepository.findOne(appUserRolePK);

生成的查询：

Hibernate: select appuserrol0_.id_app as id_app1_2_0_, appuserrol0_.id_role as id_role2_2_0_, appuserrol0_.id_user as id_user3_2_0_, appuserrol0_.state as state4_2_0_, app1_.id as id1_0_1_, app1_.app as app2_0_1_, app1_.descr as descr3_0_1_, role2_.id as id1_4_2_, role2_.id_app as id_app3_4_2_, role2_.role as role2_4_2_, app3_.id as id1_0_3_, app3_.app as app2_0_3_, app3_.descr as descr3_0_3_, user4_.id as id1_5_4_, user4_.mail as mail2_5_4_, user4_.password as password3_5_4_, user4_.username as username4_5_4_ from security.app_user_role appuserrol0_ left outer join security.app app1_ on appuserrol0_.id_app=app1_.id left outer join security.role role2_ on appuserrol0_.id_role=role2_.id left outer join security.app app3_ on role2_.id_app=app3_.id left outer join security.user user4_ on appuserrol0_.id_user=user4_.id where appuserrol0_.id_app=? and appuserrol0_.id_role=? and appuserrol0_.id_user=?

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提前感谢

这是映射对象时的常规行为（加载了eager，默认情况下

@ManyToOne

）

对于示例中的第一个查询，将接收映射对象的标识符：

appuserrol0_.id_app as id_app1_2_, appuserrol0_.id_role as id_role2_2_, appuserrol0_.id_user as id_user3_2_,

如果在当前持久性上下文中还不可用，则以下查询将使用每个对象本身的值（满足映射的获取策略所需的值）来获取它们。如果它们已经存在于（第一级）缓存中，则不需要进行其他选择

如果要重写此行为，请自行编写HQL，也可以使用

@Query

注释在Spring数据JPA存储库中执行此操作：

@Query("FROM AppUserRole aur JOIN FETCH aur.app a JOIN FETCH aur.user u JOIN FETCH aur.role r WHERE a =:app AND u =:user")
Set<AppUserRole> findByAppAndUser(@Param("app") App app, @Param("user") User user);

@Query（“来自AppUserRole aur JOIN FETCH aur.app a JOIN FETCH aur.user u JOIN FETCH aur.role r，其中a=：app和u=：user”）
设置findByAppAndUser（@Param（“app”）app app、@Param（“user”）user）；

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请记住，当您将此查询与

joinfetch

语句一起使用时，您将失去延迟加载方法的所有优点。

谢谢，joinfetch就是答案。我一直在使用fetch模式研究一级缓存，但我没有找到示例，欢迎使用。基本上，只要当前持久性上下文/会话处于打开状态，一级缓存就会存储已查询的实体，请参见我前面评论中的链接。当一个实体在此缓存中可用并且再次被查找（通过identifer）时，无需再次访问数据库。我还纠正了代码片段中的一个小复制粘贴问题：）

@Query("FROM AppUserRole aur JOIN FETCH aur.app a JOIN FETCH aur.user u JOIN FETCH aur.role r WHERE a =:app AND u =:user")
Set<AppUserRole> findByAppAndUser(@Param("app") App app, @Param("user") User user);