Merge detached sub-class entity (JPA InheritanceType.SINGLE_TABLE) org.hibernate.WrongClassException

[H Paul]

(Not sure what the issue is, could be Java related or flow design.
the title may be misleading (99% ?), but for the background, I put below 5 points. 1M Thanks.)


1. Simple Object Model: ProspectCustomer extends Customer
2. I use Restful GET to find the prospect customer. I got the returned prospect customer in the form of JSON.
3. I use Restful PUT to update the prospect customer. [In the backend, JPA used merge operation.]

Code for point 3: Rest Code 

@PUT
@Consumes({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML})
@Override
public void updateCustomer(Customer customer) {
	logger.debug(customer);
	this.customerService.updateCustomer(customer);

}
	
Code for point 3: JPA code

@Transactional
@Override
public void updateCustomer(Customer customer) {
	entityManager.merge(customer);
}

I got below exception. 

javax.persistence.PersistenceException: org.hibernate.WrongClassException: Object with id: null was not of the specified subclass: concepts.domain.Customer (class of the given object did not match class of persistent copy)
	at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1361)
	at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1289)
	at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1295)
	at org.hibernate.ejb.AbstractEntityManagerImpl.merge(AbstractEntityManagerImpl.java:876)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:240)
	at $Proxy40.merge(Unknown Source)

4. For debugging, If I changed Customer to ProspectCustomer in Rest code as below, then it's OK for JPA code.

@PUT
@Consumes({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML})
@Override
public void updateCustomer(ProspectCustomer customer) {
	logger.debug(customer);
	this.customerService.updateCustomer(customer);

}

5. Now, if I want to keep Customer parameter (not ProspectCustomer) in my Rest code, then what need to be done in terms of correction?


===============================================================================

Code for point 1:

@Entity
@Table(name = "CUSTOMER")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "CUSTOMER_TYPE", discriminatorType = DiscriminatorType.STRING)
@DiscriminatorValue("C")
@XmlRootElement
public class Customer implements Serializable {

	....
}

@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorValue("P")
@XmlRootElement
public class ProspectCustomer extends Customer implements Serializable{
	public ProspectCustomer() {
		super();
	}

}

[H Paul]

Changed made to Code for point 3: JPA code . Worked.

    @Transactional
 	@Override
 	public void webUpdateCustomer(Customer customer) {
 	//Added, Find
     	Customer managedCustomer = entityManager.find(Customer.class, customer.getId());
     	//Added, Then set
     	managedCustomer.setContactInfo(customer.getContactInfo());
     	
 	entityManager.merge(managedCustomer);
 	}