java - JPA 和 Hibernate 缺少 INNER JOIN ON 子句

Question

我试图找出我在 JPA/Hibernate 方面做错了什么。

我有一个包含两个表的数据库:banner 和bannerlinks。

 banner
 +-------------------------------------------+
 | id | logo | studyId | textColor | bgColor |
 +-------------------------------------------+
 |  1 | xx   |  17     |  green    | red     |
 +-------------------------------------------+

 bannerlink
 +----------------------------------------+
 | id | bannerId| label | text | image    |
 +----------------------------------------+
 |  1 | 1       |  About| Abt..| xxx      |
 +----------------------------------------+
 |  2 | 1       |  Beta | Bet..| xxx      |
 +----------------------------------------+
 |  2 | 1       |  Cont | Ctc..| xxx      |
 +----------------------------------------+

以及每个的实体类

@Entity
@Table(name="bannerlink")
public class BannerLink{
    @Id
    @GeneratedValue
    private int id;
    private String label;

    @ManyToOne
    @JoinColumn(name = "bannerId")
    private Banner banner;
    ...
}


@Entity
@Table(name = "banner")
public class Banner {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    private String logo;
    private String textColor;
    private String backgroundColor;
    private int studyId;

    @OneToMany(
        mappedBy = "banner",
        cascade = CascadeType.ALL,
        fetch=FetchType.LAZY,
        targetEntity = BannerLink.class
    )
    private List<BannerLink> links;

    public Banner() {
    }
    ...
 } 

我还定义了一个 DAO。

public interface BannerDAO extends JpaRepository<Banner, Integer> {

    @Query("select distinct banner FROM Banner banner join BannerLink bl where banner.studyId = :studyId")
    Banner getBannerByStudyId(@Param("studyId") int studyId);
}

但是，当我运行 DAO 方法 getBannerByStudyId 时，出现异常 “com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException:您的 SQL 语法有错误；请检查与您的 MariaDB 服务器版本相对应的手册，以了解在第 1 行的“wherebanner0_.studyId=17”附近使用的正确语法”

打印 Hibernate 生成的 RAW SQL 显示 INNER JOIN ON 子句中缺少参数。

 Hibernate: 
     select
         distinct banner0_.id as id1_0_,
         banner0_.backgroundColor as backgrou2_0_,
         banner0_.logo as logo3_0_,
         banner0_.studyId as studyId4_0_,
         banner0_.textColor as textColo5_0_ 
     from
         banner banner0_ 
     inner join
         bannerlink bannerlink1_ 
             on 
     where
         banner0_.studyId=?

知道我做错了什么吗？

Answer 1

您的查询有误。正确的查询是 >

"select distinct banner FROM Banner banner fetch join banner.links where banner.studyId = :studyId"

我理解你的问题的方式是，你想要获取一个 StudyId 的所有横幅及其相应的链接。如果我错了请纠正我。上面的查询正在完成这项工作。