Java 如何在hibernate 3中映射派生标识?
我有以下情况:Java 如何在hibernate 3中映射派生标识?,java,hibernate-mapping,hibernate3,Java,Hibernate Mapping,Hibernate3,我有以下情况: @Entity class A{ @Id @SequenceGenerator(name = "SEQ_AID", sequenceName = "SEQ_AID") @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_AID") private Long aId; @OneToOne(fetch=FecthType.LAZY,optional=false,cascade=
@Entity
class A{
@Id
@SequenceGenerator(name = "SEQ_AID", sequenceName = "SEQ_AID")
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_AID")
private Long aId;
@OneToOne(fetch=FecthType.LAZY,optional=false,cascade=CascadeType.ALL)
private B b;
...
}
@Entity
class B{
@Id
private A a;
...
}
换句话说:a和B之间有一个一对一的关联。B是一个弱实体,它的Id是从a类派生的
我已经测试了一些解决方案,如上面提到的在@OneToOne下添加@PrimaryKeyJoinColumn。但是我得到了这个错误:“org.hibernate.id.IdentifierGenerationException:在调用save()之前必须手动分配这个类的id:B”我不知道它是否与本例相关,但我使用的是Oracle 11g 已更新 我想我是对的。以下是我的问题的实际状态:
@Entity
class A{
@Id
@SequenceGenerator(name = "SEQ_AID", sequenceName = "SEQ_AID")
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_AID")
private Long aId;
@OneToOne(fetch=FecthType.LAZY,optional=false,cascade=CascadeType.ALL)
@PrimaryKeyJoinColumn(name="aId")
private B b;
...
}
@Entity
class B{
@Id
@OneToOne
@JoinColumn(name="aId)
private A a;
...
}
现在的错误有点不同:
java.sql.SQLException: ORA-00904: "B"."A": invalid identifier
它正在尝试在表B中查找列A(而不是AID)。我不知道如何指定列名为B.AID而不是B.A。您在实体B上尝试过吗
@Entity class B {
@Id @OneToOne
@JoinColumn(name = "table_a_id") //put the correct column name for A's pk here
private A a;
....
}
你在实体B上试过吗
@Entity class B {
@Id @OneToOne
@JoinColumn(name = "table_a_id") //put the correct column name for A's pk here
private A a;
....
}
接下来我解决了我的问题 正确答案是:
@Entity
public class A {
@Id
@GeneratedValue
@Column(name = "aId")
private Long id;
@OneToOne(fetch = FetchType.LAZY, optional=false, cascade = CascadeType.ALL, mappedBy = "a")
private B b;
...
}
@Entity
@org.hibernate.annotations.GenericGenerator(name="a-primarykey", strategy="foreign", parameters={@org.hibernate.annotations.Parameter(name="property", value="a")})
public class B {
@Id
@GeneratedValue(generator = "a-primarykey")
@Column(name = "aId")
private Long id;
@OneToOne
@PrimaryKeyJoinColumn
private A a;
...
}
接下来我解决了我的问题 正确答案是:
@Entity
public class A {
@Id
@GeneratedValue
@Column(name = "aId")
private Long id;
@OneToOne(fetch = FetchType.LAZY, optional=false, cascade = CascadeType.ALL, mappedBy = "a")
private B b;
...
}
@Entity
@org.hibernate.annotations.GenericGenerator(name="a-primarykey", strategy="foreign", parameters={@org.hibernate.annotations.Parameter(name="property", value="a")})
public class B {
@Id
@GeneratedValue(generator = "a-primarykey")
@Column(name = "aId")
private Long id;
@OneToOne
@PrimaryKeyJoinColumn
private A a;
...
}
对谢谢你的回答,但它不起作用,同样的错误。正如文章所说,似乎不可能将级联与派生标识一起使用……是的。谢谢你的回答,但它不起作用,同样的错误。正如文章所说,似乎不可能将级联与派生标识一起使用……如果您使用Hibernate 3.5,这可能会有所帮助:如果您使用Hibernate 3.5,这可能会有帮助: