Question

如何在Hibernate实体类中创建下一类关系？用户通过创建消息（发送者，接收者，消息）向另一个用户发送消息。 DB看起来像这样：

+-----------------------------------+
|                user               |
+-----------------------------------+
| id |   nickname  |    password    |
+----+-------------+----------------+
|  1 |    admin    |      pass      |
+----+-------------+----------------+

+------------------------------------------------+
|                     message                    |
+-----------------------------------|------------+
| id |  sender_id  |  receiver_id   |  message_t |
+----+-------------+----------------+------------+
|  1 |      10     |       12       |      hi    |
+----+-------------+----------------+------------+

实体类必须如何？

@Entity 
@Table(name="profiles")
public class Message {

    @Id
    @Column(name="id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ManyToOne
    @JoinColumn(name = "sender")
    private User sender;

    @ManyToOne
    @JoinColumn(name = "receiver")
    private User receiver;

    @Column(name = "message")
    String message;
}

@Entity
@Table(name = "users")
public class User {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @OneToMany(mappedBy = )
    List<Message> messages;
}

映射...什么？我需要找到当前用户作为发送者OR / AND接收者存在的所有消息。（＆＃34; AND＆＃34;因为用户可以向自己发送消息）。

Answer 1

如果您需要查找用户发送或接收的消息，则您在消息实体和用户映射中拥有所有信息对您无关紧要。

从消息m中选择m，其中m.sender！= m.receiver和（m.sender =：user或 m.receiver =：用户）
。

关系有两种类型：单向和双向。

如果在用户的实体映射中你应该保留有关发送者和reciver的信息（你已经在Message中有这个信息）那么双向关系：

@Entity
@Table(name = "users")
public class User {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @OneToMany(mappedBy = receiver)
    private List<Message> messagesRecived;

    @OneToMany(mappedBy = sender)
    private List<Message> messagesSended;
}

Hibernate用户消息关系

1 个答案: