给定一个表( MY_TABLE_A
),它在每次新插入时自动递增其 id(即数据库中的第一条记录的 ID 属性为 1,第二条记录的 ID 属性设置为 2,第三条记录的 ID 属性为 2) ID 属性设置为 3)。我所说的 ID 是表的主键。
我还有另一个表 ( MY_TABLE_B
),它引用原始表的主键。当我尝试将两者持久保存到我的 Oracle 数据库时,我得到 org.hibernate.id.IdentifierGenerationException: ids for this class must be manually assigned before calling save()
我想要完成的任务:每当我将一个对象持久化到 MY_TABLE_A
时,我要MY_TABLE_B
插入一个与 MY_TABLE_A
具有相同 ID 的对象获取,因为它是自动递增的(在插入之前不知道下一个值是什么)。澄清一下,表 A 中的一个 id 在表 B 中应该只有一个匹配的 ID
下面是我的一些代码片段:
头等舱:
@Entity
@Table(name = "MY_SCHEMA.MY_TABLE_A")
@Component
public class FirstClass implements Serializable {
@Id
@SequenceGenerator(name = "MY_SEQ", sequenceName = "MY_SCHEMA.MY_SEQ", allocationSize = 1)
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "MY_SEQ")
@Column(name = "MY_ID")
private Integer myId;
// more variables, getters/setters
}
<小时/>
二等:
@Entity
@Table(name = "MY_SCHEMA.MY_TABLE_B")
@SecondaryTable(name = "MY_SCHEMA.MY_TABLE_A", pkJoinColumns = @PrimaryKeyJoinColumn(name = "MY_ID", referencedColumnName = "MY_ID"))
@Component
public class SecondClass {
@Id
@Column(name = "MY_ID")
private Integer myId;
// more variables, getters/setters
}
<小时/>
服务层片段,我在 Oracle 中为每个服务层插入新条目:
firstClassService.insert();
secondClassService.insert();
<小时/>
详细信息insert()
对于头等舱服务:
public void insert() {
FirstClass obj = new FirstClass();
getCurrentSession().persist(obj);
}
<小时/>
insert()
对于第二类服务:
public void insert() {
SecondClass obj = new SecondClass();
getCurrentSession().persist(obj);
}
更新
FirstClass 现在的样子:
@Entity
@Table(name = "MY_SCHEMA.MY_TABLE_A")
@Component
public class FirstClass implements Serializable {
@Id
@SequenceGenerator(name = "MY_SEQ", sequenceName = "MY_SCHEMA.MY_SEQ", allocationSize = 1)
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "MY_SEQ")
@Column(name = "MY_ID")
@OneToOne(mappedBy = "myId")
private Integer myId;
}
<小时/>
二等:
@Entity
@Table(name = "MY_SCHEMA.MY_TABLE_B")
@SecondaryTable(name = "MY_SCHEMA.MY_TABLE_B", pkJoinColumns = @PrimaryKeyJoinColumn(name = "MY_ID", referencedColumnName = "MY_ID"))
@Component
public class SecondClass implements Serializable {
@Id
@JoinColumn(name = "MY_ID", referencedColumnName = "MY_ID")
@OneToOne
private Integer restRequestId;
}
最佳答案
映射应如下所示:
@Entity
@Table(name = "MY_SCHEMA.MY_TABLE_A")
@Component
public class FirstClass implements Serializable {
@Id
@SequenceGenerator(name = "MY_SEQ", sequenceName = "MY_SCHEMA.MY_SEQ", allocationSize = 1)
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "MY_SEQ")
@Column(name = "MY_ID")
private Long myId;
@OneToOne(mappedBy = "firstClass", cascade = CascadeType.ALL)
private SecondClass secondClass;
}
@Entity
@Table(name = "MY_SCHEMA.MY_TABLE_B")
@Component
public class SecondClass implements Serializable {
@Id
@JoinColumn(name = "MY_ID", referencedColumnName = "MY_ID")
@OneToOne
private FirstClass firstClass;
}
设置级联选项后,您只需调用保存firstClass:关联的secondClass将自动保留 - 假设您在内存模型中设置了关系的两侧,即
firstClass.setSecondClass(secondClass);
secondClass.setFirstClass(firstClass);
关于java - 如何使用 JPA/Hibernate 在 child 的 id 中引用 parent 的 id?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38838999/