如何在 EJB 3.0 Entity-Beans (JPA) 中创建单向关系?
例如,客户知道订单,但订单没有客户的任何方法。 使用(@OneToMany 或@OneToOne 或@ManyToMany)
问候
最佳答案
下面是使用 JPA 2.0 建立单向 @OneToMany
关系的方法:
@Entity
public class Customer {
@Id
@Column(name="cust_id")
private long id;
...
@OneToMany
@JoinColumn(name="owner_id", referencedColumnName="cust_id")
private List<Order> order;
...
}
@Entity
public class Order {
@Id
@Column(name="order_id")
private long id;
...
}
关系数据库:
客户:
+---------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+---------+------+-----+---------+-------+
| cust_id | int(11) | NO | PRI | NULL | |
+---------+---------+------+-----+---------+-------+
顺序:
+----------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+---------+------+-----+---------+-------+
| order_id | int(11) | NO | PRI | NULL | |
| owner_id | int(11) | NO | MUL | NULL | |
+----------+---------+------+-----+---------+-------+
关于java - Entity-Bean (JPA) 中的单向关系,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/3515756/