java.lang.ClassCastException: org.hibernate.mapping.SingleTableSubclass不能强制转换为org.hibernate.mapping.RootClass
java.lang.ClassCastException: org.hibernate.mapping.SingleTableSubclass不能强制转换为org.hibernate.mapping.RootClass
提问于 2020-09-06 12:12:34
我有两个类，一个父类和一个子类，我使用了this解决方案来定义混合继承策略，但是当使用maven编译时，我得到了一个错误。
父类：
@Entity
@Table(name="ITEMS")
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="ITEM_CATEGORY",discriminatorType=DiscriminatorType.INTEGER)
public class Item {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name = "ITEM_ID")
protected Long itemId;
.
.
.}子类：
@Entity
@SecondaryTable(name="TASKS", pkJoinColumns =
{@PrimaryKeyJoinColumn(name = "ITEM_ID", referencedColumnName = "ITEM_ID")})
@DiscriminatorValue(value=ItemCategory.Values.TASK)
public class Task extends Item {
//no @Id field}错误：
java.lang.IllegalStateException: Failed to load ApplicationContext
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Invocation of init method failed; nested exception is java.lang.ClassCastException: org.hibernate.mapping.SingleTableSubclass cannot be cast to org.hibernate.mapping.RootClass
Caused by: java.lang.ClassCastException: org.hibernate.mapping.SingleTableSubclass cannot be cast to org.hibernate.mapping.RootClasspom.xml：
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.0.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-rest</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>DDL：
CREATE TABLE ITEMS(
ITEM_ID bigint auto_increment primary key,
.
.
.
FOREIGN KEY(RELATED_TO_ITEM) references ITEMS(ITEM_ID)
);
CREATE TABLE TASKS( #INCLUDES REPEATED TASKS, ONETIME TASKS, LEARNING DUTY AND RESPONSES
ITEM_ID bigint primary key,
.
.
.
FOREIGN KEY(ITEM_ID) references ITEMS(ITEM_ID)
);回答 1
Stack Overflow用户
发布于 2020-09-07 00:39:42
我试着在hibernate版本5.2.14.Final (spring-boot-starter-data-jpa 2.0.0.RELEASE)中使用你的映射(做了一些小改动)：
表：
CREATE TABLE ITEMS (
ITEM_ID bigint auto_increment primary key,
ITEM_CATEGORY bigint,
RELATED_TO_ITEM bigint,
FOREIGN KEY(RELATED_TO_ITEM) references ITEMS(ITEM_ID)
);
insert into ITEMS
values (1, 1, null), (2, 1, 1), (3, 0, 1), (4, 1, 2);
CREATE TABLE TASKS(
ITEM_ID bigint primary key,
code varchar(100),
FOREIGN KEY(ITEM_ID) references ITEMS(ITEM_ID)
);
insert into TASKS
values (1, 'TASK 1'), (2, 'Task 2'), (4, 'Task 4');Hibernate映射：
@Entity
@Table(name = "ITEMS")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="ITEM_CATEGORY", discriminatorType = DiscriminatorType.INTEGER)
public class Item
{
private Long itemId;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "ITEM_ID")
public Long getItemId()
{
return itemId;
}
public void setItemId(Long itemId)
{
this.itemId = itemId;
}
}
@Entity
@SecondaryTable(name="TASKS", pkJoinColumns = {
@PrimaryKeyJoinColumn(name = "ITEM_ID", referencedColumnName = "ITEM_ID")
})
@DiscriminatorValue("1")
public class Task extends Item
{
private String code;
@Column(table = "TASKS", name = "code")
public String getCode()
{
return code;
}
public void setCode(String code)
{
this.code = code;
}
}
@Entity
@DiscriminatorValue("0")
public class Job extends Item
{
}和用于选择测试的简单代码：
List<Item> items = session.createQuery("select i from Item i", Item.class).getResultList();将生成以下sql：
/* select i from Item i */
select
item0_.ITEM_ID as ITEM_ID2_0_,
item0_1_.code as code1_1_,
item0_.ITEM_CATEGORY as ITEM_CAT1_0_
from DB_A.ITEMS item0_
left outer join DB_A.TASKS item0_1_ on item0_.ITEM_ID=item0_1_.ITEM_ID和插入测试：
Task task = new Task();
task.setCode("my new task 1");
session.persist(task);将生成以下sql：
/* insert com.sternkn.hibernate.model.Task */
insert into DB_A.ITEMS(ITEM_CATEGORY)
values (1)
/* insert com.sternkn.hibernate.model.Task */
insert into DB_A.TASKS(code, ITEM_ID)
values (?, ?)如果没有帮助，请提供异常的完整堆栈跟踪和继承层次结构中所有实体的完整代码。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/63760632
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