我最近开始使用 Hibernate,并试图理解所有注释并确保我正确地做事。我有两个表“user”和“user_friends”,类似于下面的
+------+------+-------+
| id | name | email |
+------+------+-------+
和用户好友表
+--------+---------+----------+
| userid | buddyid | accepted |
+--------+---------+----------+
现在在 SQL 中我运行了一个类似于以下内容的查询
SELECT u.id AS id, u.name AS username, u.email AS email FROM user_friends
INNER JOIN users AS u ON u.id = '1' WHERE buddyid = '2' AND ACCEPTED = 1 UNION ALL
SELECT u.id as id, u.name AS username, u.email AS email FROM user_friends
INNER JOIN users AS u ON u.id = '2' WHERE buddyid = '1' AND ACCEPTED = 1;
我在 Java 中设置了两个类,其方式与此类似
@Entity
@Table(name="users")
public class User {
@Id
@GeneratedValue
private int id;
private int name;
private int email;
@OneToMany(fetch=UserBuddy.class, mappedBy="user", fetch=FetchType.LAZY)
@JoinColumn(name="userid")
private Set<UserBuddy> _buddies;
}
@Entity
@Table(name="user_friends")
public class UserBuddy {
@ManyToOne
@JoinColumn(name="id")
private User friendId;
private int id;
private int name;
private int email;
}
我不知道如何从用户表中获取 user_friends 姓名和电子邮件。有人可以提供任何帮助吗?
最佳答案
由于您的 UserBuddy 中有 User 对象,因此只需引用该对象
@Entity
@Table(name="user_friends")
public class UserBuddy
{
@ManyToOne
@JoinColumn(name="id")
private User friend; // This is a User not an id
public String getEmail()
{
return friend.getEmail();
}
}
关于Java Hibernate 注解 @JoinTable 关系,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/11474082/