I am getting an exception: "Caused by: javax.persistence.EntityExistsException: A different object with the same identifier value was already associated with the session: com.efl.mobility.puma.dao.model.content.ProductDL#ukdipabk" when I get (find method) an entity by its compound key. This exception only be thrown when one entity, at least, of compound key is previously loaded in session.

Siemple Entity:

@Entity(name="Customer")
public class CustomerDL implements Serializable

Entity with compound key:

public class SubscriptionDL implements Serializable {

private SubscriptionIdDL subscriptionId;

@EmbeddedId
public SubscriptionIdDL getSubscriptionId()

public void setSubscriptionId(SubscriptionIdDL subscriptionId)

}

Embedded id:

public class SubscriptionIdDL implements Serializable {

private CustomerDL customer;
private ProductDL product;

@OneToOne
@JoinColumn(name="CUS_ID", referencedColumnName="CUS_ID", nullable=false)
public CustomerDL getCustomer()

public void setCustomer(CustomerDL customer)

@ManyToOne
@JoinColumn(name="CNT_PRODUCT_COD", referencedColumnName="CNT_PRODUCT_COD", nullable=false)
public ProductDL getProduct()

public void setProduct(ProductDL product)

}

Steps to reproduce the exception:

1) Load with session find (by id) method an entity of type CustomerDL.
2) Create an entity (also fails if this entity is loaded from session) of type ProductDL and fill its id.
3) Create compound key (SubscriptionIdDL) with (1) and (2) entities.
4) Load with session find (by id) method an entity of type SubscriptionDL using (3) generated Key.

Example (using a service layer):

ProductSL productSL=productService.get("ukdipabk");
CustomerSL customerSL2=new CustomerSL();
customerSL2.setCustomerId(2L);

subscriptionIdSL=new SubscriptionIdSL();
subscriptionIdSL.setProduct(productSL);
subscriptionIdSL.setCustomer(customerSL2);

subscriptionService.get(subscriptionIdSL); //launch "already associated exception"

In Hibernate 4 version using exactly same code this work fine.