java.lang.ClassCastException: org.hibernate.mapping.SingleTableSubclass cannot be cast to org.hibernate.mapping.RootClass

Question

I have 2 classes one parent and one child, I used this workaround to define mixed inheritance strategy, however when compiling with maven, I am getting an error.

Parent class:

@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;
.
.
.}

Child class:

 @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}

error:

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:

    <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)
);

Could you please provide DDL of your tables.

SternK
– SternK

2020-09-06 13:08:59 +00:00
Commented Sep 6, 2020 at 13:08 — SternK
– SternK, Commented Sep 6, 2020 at 13:08
@SternK ,added , thanks

osama yaccoub
– osama yaccoub

2020-09-06 13:33:53 +00:00
Commented Sep 6, 2020 at 13:33 — osama yaccoub
– osama yaccoub, Commented Sep 6, 2020 at 13:33

SternK · Accepted Answer · 2020-09-06 16:39:41Z

I tried to use your mapping (with minor changes) with exactly your hibernate version 5.2.14.Final (spring-boot-starter-data-jpa 2.0.0.RELEASE):

Tables:

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 mapping:

@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
{

}

And simple code for select testing:

List<Item> items = session.createQuery("select i from Item i", Item.class).getResultList();

will generate the following 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

And insert testing:

Task task = new Task();
task.setCode("my new task 1");
session.persist(task);

will generate the following 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 (?, ?)

If it will not help, please provide the full stack trace of your exception and full code of all entities from your inheritance hierarchy.

thanks alot for your effort first, so you mean it worked from your side with the provided structure?

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