Java 每个具体类使用hibernate继承表时创建别名时出错
我有一个模型,在这个模型中,我实现了每个具体类的表。因此,我有一个抽象类,它在多个表中具有公共属性。我有以下实体Java 每个具体类使用hibernate继承表时创建别名时出错,java,hibernate,polymorphism,Java,Hibernate,Polymorphism,我有一个模型,在这个模型中,我实现了每个具体类的表。因此,我有一个抽象类,它在多个表中具有公共属性。我有以下实体 @Entity @Inheritance(strategy=InheritanceType.TABLE_PER_CLASS) public abstract class BaseForm{ @Id @GeneratedValue(strategy = GenerationType.TABLE) protected Long id;
@Entity
@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
public abstract class BaseForm{
@Id
@GeneratedValue(strategy = GenerationType.TABLE)
protected Long id;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id=id;
}
@Column(name = "submission_date")
protected Date submissionDate;
public Date getSubmissionDate() {
return submissionDate;
}
public void setSubmissionDate(Date submissionDate) {
this.submissionDate=submissionDate;
}
}
@Entity
@Table(name = "form_a")
public class FormA extends BaseForm{
@OneToMany(cascade = CascadeType.ALL, mappedBy = "formA", fetch = FetchType.LAZY)
@Cascade(value = org.hibernate.annotations.CascadeType.DELETE_ORPHAN)
@Fetch(FetchMode.SUBSELECT)
@OrderBy("id")
protected List<UserForm> userForms = new ArrayList<UserForm>();
}
@Entity
@Table(name = "form_b")
public class FormB extends BaseForm{
@OneToMany(cascade = CascadeType.ALL, mappedBy = "formB", fetch = FetchType.LAZY)
@Cascade(value = org.hibernate.annotations.CascadeType.DELETE_ORPHAN)
@Fetch(FetchMode.SUBSELECT)
@OrderBy("id")
protected List<UserForm> userForms = new ArrayList<UserForm>();
}
@Entity
@Table(name = "user_form")
public class UserForm {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
protected Long id;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
@ManyToOne(optional = true)
protected FormA formA;
@ManyToOne(optional = true)
protected FormB formB;
@ManyToOne(optional = true)
protected User user;
下面是生成的hibernate查询
SELECT COUNT(*) AS y0_
FROM
(SELECT id,
submissionDate,
1 AS clazz_
FROM form_a
UNION
SELECT id,
submissionDate,
2 AS clazz_
FROM form_b
) this_
INNER JOIN user_form userforms1_
ON this_.id=userforms1_.formA_id
INNER JOIN user_form userforms1_
ON this_.id=userforms1_.formB_id
WHERE (userforms1_.formA IS NOT NULL
OR userforms1_.formB IS NOT NULL)
你知道会有什么问题吗。如何解决这个问题?您使用超类别名访问子类字段,这在概念上是错误的(虽然在某些情况下有效,但显然并不总是如此)
您应该考虑将<代码>用户窗体< /代码>转换为基类,或者将查询转换为类似的内容(JPQL,将其转换成等价的标准):
您使用超类别名访问子类字段,这在概念上是错误的(虽然在某些情况下有效,但显然并不总是如此)
您应该考虑将<代码>用户窗体< /代码>转换为基类,或者将查询转换为类似的内容(JPQL,将其转换成等价的标准):
谢谢你抽出时间回答我的问题。但实际上,hql并不能解决这个问题,因为FormA和FormB每个人都有自己的id序列。所以我们有可能在形式上有ID10,在形式上有另一个ID10。在这种情况下,恐怕你们会遇到比这更大的问题。以下操作的预期结果是什么:
entityManager.find(BaseForm.class,10)
(或Hibernate会话的等效操作
)?我知道@GeneratedValue(strategy=GenerationType.TABLE)将处理所有实体中ID的唯一性。感谢您抽出时间回答我的问题。但实际上,hql并不能解决这个问题,因为FormA和FormB每个人都有自己的id序列。所以我们有可能在形式上有ID10,在形式上有另一个ID10。在这种情况下,恐怕你们会遇到比这更大的问题。以下操作的预期结果是什么:entityManager.find(BaseForm.class,10)
(或使用Hibernate会话的等效操作
)?我知道@GeneratedValue(strategy=GenerationType.TABLE)将处理所有实体中ID的唯一性。
SELECT COUNT(*) AS y0_
FROM
(SELECT id,
submissionDate,
1 AS clazz_
FROM form_a
UNION
SELECT id,
submissionDate,
2 AS clazz_
FROM form_b
) this_
INNER JOIN user_form userforms1_
ON this_.id=userforms1_.formA_id
INNER JOIN user_form userforms1_
ON this_.id=userforms1_.formB_id
WHERE (userforms1_.formA IS NOT NULL
OR userforms1_.formB IS NOT NULL)
select bf from BaseForm bf
where bf.id in (select fa.id from FormA fa join fa.userForms)
or bf.id in (select fb.id from FormB fb join fb.userForms)