Hibernate HQL用于连接非映射表 [英] Hibernate HQL for joining non-mapped tables

问题描述

我有一个名为Kurs的实体：

  @Entity 
 public class Kurs {
 @I $ 
 @GeneratedValue（strategy = GenerationType.AUTO）
 private long kursId; 
私人字符串名称; 
 // Accessors .... 
} 
  

分类：

  @Entity 
公共类分类{
 
 @Id 
 @GeneratedValue（strategy = GenerationType.AUTO）
 private long kategoriId; 
私人字符串名称; 
 
 @ManyToMany（cascade = CascadeType.ALL）
 @JoinTable（name =KursKategori，joinColumns = {@JoinColumn（name =kategoriId）}，inverseJoinColumns = {@JoinColumn name =kursId）}）
 private List< Kurs> kursList; 
 // Accessors .... 
} 
  

现在我正在构建一个KursDao ，这将有一个方法来获取kategoriId的Kurs列表。但我无法让加入为我工作。
习惯于SQL我通常会认为查询应该是这样的：

$ b $ $ $ $ p $ getHibernateTemplate（）。find（ from Kurs as k INNER JOIN KursKategori kk ON k.kursId = kk.kursId AND kk.kategoriId =？，kategoriId）;

但是这不起作用，我不能得到任何这样的工作。我不想创建一个KursKategori类，因为它只是一个映射表。
有没有办法将非映射表KursKategori连接到映射表kurs，所以我只会得到正确Kategori中的Kurs？

解决方案

在HQL中，您只能加入实体之间的映射关系。然而，你有这样的关系，所以你可以使用它：

  select kurs from Kategori kat join kat.kursList kurs where kat.kategoriId =？ 
  

I have an entity called "Kurs":

@Entity
public class Kurs {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long kursId;
    private String name;
    //Accessors....
}

And also an entity called "Kategori":

@Entity
public class Kategori {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long kategoriId;
    private String name;

    @ManyToMany(cascade = CascadeType.ALL)
    @JoinTable (name = "KursKategori", joinColumns = {@JoinColumn(name = "kategoriId")}, inverseJoinColumns = {@JoinColumn(name = "kursId")})
    private List<Kurs> kursList;
    // Accessors....
}

Now im building a KursDao, that will have a method to fetch a list of Kurs by the kategoriId. But im unable to get the join to work for me. Being used to SQL i would normally think the query should be like this:

getHibernateTemplate().find("from Kurs as k INNER JOIN KursKategori kk ON k.kursId = kk.kursId AND kk.kategoriId = ?", kategoriId);

But this doesnt work and i cant get anything like this to work. I do not want to create an Class of the KursKategori since it is only a mapping table anyway. Is there a way to join the non-mapped table KursKategori to the mapped table kurs so i will only get the Kurs that is in the correct Kategori?

解决方案

In HQL you can only join on mapped relationships between entities. However, you have such a relationship, so that you can use it:

select kurs from Kategori kat join kat.kursList kurs where kat.kategoriId = ?

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