java.lang.classcastexception:org.hibernate.mapping.singletablesubclass不能强制转换为org.hibernate.mapping.rootclass

z6psavjg 于 2021-07-04 发布在 Java

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我有两个类，一个是父类，一个是子类，我用这个变通方法定义了混合继承策略，但是当用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;
.
.
.}

儿童班：

@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.RootClass

pom.xml文件：

<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地址：

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)
);

Java spring-boot spring-data-jpa Hibernate jpa

来源：https://stackoverflow.com/questions/63760632/java-lang-classcastexception-org-hibernate-mapping-singletablesubclass-cannot-b

1条答案

按热度按时间

xqk2d5yq1#

我尝试将您的Map（稍作修改）与hibernate版本5.2.14.final（spring boot starter数据jpa 2.0.0.release）完全配合使用：
table：

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');

休眠Map：

@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
{

}

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以及继承层次结构中所有实体的完整代码。

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java.lang.classcastexception:org.hibernate.mapping.singletablesubclass不能强制转换为org.hibernate.mapping.rootclass

1条答案

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