Hibernate在用@ManyToOne查询时返回null hql [英] Hibernate returns null hql in query with @ManyToOne

问题描述

首先，我很抱歉如果我的问题看起来有些业余，但我对hibernate / jpa和mysql的知识有限。

那么，我有以下实体：

用户实体

  @Entity 
 @Table（name =user）
 public class User {
 @Id 
 @GeneratedValue（strategy = GenerationType.AUTO）
 @Column（name = id_user）
 private long idUser; 
 
 @Column（nullable = false）
私有字符串名称; 
 
 @Column（nullable = false）
 private String email; 
 
 @ManyToOne（可选= true，fetch = FetchType.EAGER）
 @JoinColumn（name =level，referencedColumnName =id_level，nullable = true）
 private水平; 
 
 @Transient 
私人长汇票; 
} 
  

从那里开始，我正在尝试执行以下mysql查询： p>

  public User findUserByEmail（String email）{
 Session session = HibernateUtil.getSessionFactory（）。openSession（）; 
 User user = null; 
 
 String hql =SELECT
 +u.idUser as idUser，
 +u.nome as nome，
 +u.level as级别，
 +（SELECT count（*）FROM UserLikes likes WHERE likes.user = u.idUser）as totalLikes
 +FROM User u WHERE u.email =：email; 
尝试{
 Query query = session.createQuery（hql）; 
 query.setString（email，email）; 
 query.setResultTransformer（Transformers.aliasToBean（User.class））; 
 user =（Usuario）query.uniqueResult（）; 
 
} catch（RuntimeException ex）{
 throw ex; 
} finally {
 session.close（）; 
} 
 
返回用户; 
 
 
 
 
 
 $ b上面的代码正常返回用户，但是当用户搜索时返回null在数据库中没有设置字段级别的值。也就是说，如果我没有错，hibernate会执行内部连接用户/级别，而不是左连接，从而使返回值为null。
 
 
 
有没有人知道如何获取在这附近？
解决方案
我认为你需要使用这个。  
 
 
  @ManyToOne //简单
 @JoinColumn（nullable = true）简单
  
并在您的查询中使用简单的方式。 
  FROM用户u WHERE u.email =：电子邮件
  
我在类似的项目中使用它并工作。  
 
 
干得好。  
First I apologize if my question seems a bit amateurish, but my knowledge with hibernate / jpa and mysql are somewhat limited.

Well, I have the following entity:

User Entity
@Entity
@Table(name = "user")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id_user")
    private Long idUser;

    @Column(nullable = false)
    private String name;

    @Column(nullable = false)
    private String email;

    @ManyToOne(optional = true, fetch = FetchType.EAGER)
    @JoinColumn(name = "level", referencedColumnName = "id_level", nullable = true)
    private Level level;

    @Transient
    private Long totalLikes;
}
From there, I'm trying to do the following mysql query:
public User findUserByEmail(String email) {
        Session session = HibernateUtil.getSessionFactory().openSession();
        User user = null;

        String hql = "SELECT "
                   + "u.idUser as idUser, "
                   + "u.nome as nome, "
                   + "u.level as level, "
                   + "(SELECT count(*) FROM UserLikes likes WHERE likes.user = u.idUser) as totalLikes "
            + "FROM User u WHERE u.email = :email";
        try {
            Query query = session.createQuery(hql);
            query.setString("email", email);
            query.setResultTransformer(Transformers.aliasToBean(User.class));
            user = (Usuario) query.uniqueResult();

        } catch (RuntimeException ex) {
            throw ex;
        } finally {
            session.close();
        }

        return user;
    }
The above code returns the User normally, however returns null when the User to search in the database do not have value set in the field level. That is, if I am not wrong, hibernate does an inner join user / level and not a left join, making returns null.

Does anyone have any idea how to get around this?
解决方案
i think you need use this. 
@ManyToOne //simple
@JoinColumn(nullable = true) simple
and in your query using simple too. 
FROM User u WHERE u.email = :email
i use this in similiar project and worked. 

Good job man. 

                        
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