如何使用hibernate标准连接多个表，其中实体关系不是直接的？

Posted 2021-03-29

我有三个实体。那些是：

@Entity
public class Organization {
    @Id
    private long id;
    @Column
    private String name;
}

@Entity
public class Book {
    @Id
    private Long id;
    @Column
    private String name;
    @ManyToOne
    private Organization organization;
}

@Entity
public class Account  {
   @Id
   private Long id;
   @Column
   private String name;
   @ManyToOne
   private Book book;
}

在这三个实体中，我想执行以下sql：

SELECT acc.name, acc.id
FROM account acc
JOIN book b on acc.book_id = b.id
JOIN organization org on b.organization_id = org.id
WHERE org.name = 'XYZ'

在这种情况下，Account实体与Organization实体没有直接关系。 Account实体通过Book有关系。我如何使用hibernate条件动态查询来实现这一点？

答案

你可以这样做：

Criteria accountCriteria = getCurrentSession().createCriteria(Account.class,"acc");
Criteria bookCriteria =  accountCriteria .createCriteria("book","b");
Criteria orgCriteria =  bookCriteria.createCriteria("organization","org");
orgCriteria.add(Restrictions.eq("name", "XYZ"));

ProjectionList properties = Projections.projectionList();
properties.add(Projections.property("name"));
properties.add(Projections.property("id"));

accountCriteria.setProjection(properties);
accountCriteria.list();

另一答案

其他方式

public List<Account> getAccountListByOrgName(String name){
    return sessionFactory.getCurrentSession().createCriteria(Account.class)
                .createAlias("book", "book")
                .createAlias("book.organization", "organization")
                .add(Restrictions.eq("organization.name", name))
                .list();
}