"No identifier specified" when using InheritanceType.JOINED

[Peter Irmstadt]

Hi!

I am using JBoss Seam and MySQL to develop a web application.
There are few kind of users that may login to my application. To reduce overhead I want to create a class for each usertype that may login.

This is what I did:

The main class:

@Entity
@Table(name = "`daLogin`")
@Inheritance(strategy = InheritanceType.JOINED)
public class Login implements Serializable
{
	private static final long serialVersionUID = 1L;
	private int intID;
	private String strLogin;
	private String strPasswort;

	public Login(){}

	@Id
	@GeneratedValue
	@Column(name="intLoginID")
	public int getIntID() {
		return intID;
	}

	public void setIntID(int intID) {
		this.intID = intID;
	}

	@Column(nullable = false, name="strLogin", unique=true, length=15 )
	public String getStrLogin() {
		return strLogin;
	}

	public void setStrLogin(String strLogin) {
		this.strLogin = strLogin;
	}

	@Column(nullable = false, name="strPasswort", length=32)
	public String getStrPasswort() {
		return strPasswort;
	}

	public void setStrPasswort(String strPasswort) {
		this.strPasswort = strPasswort;
	}

}
    

and this a sample "child"

@Entity
@Table(name = "`daLoginBenutzer`")
public class LoginBenutzer extends Login {
	private static final long serialVersionUID = 1L;
	private String strFirma;

	@Column(name = "strFirma", length = 75, nullable = false)
	public String getStrFirma() {
		return strFirma;
	}
	public void setStrFirma(String strFirma) {
		this.strFirma = strFirma;
	}
}

But when trying to publish these two classes I get the following error:

org.hibernate.AnnotationException: No identifier specified for entity: de.my-project.entity.LoginBenutzer

I looked for some examples but none of them had a primary key on the child entity. Where is my mistake? Whan can I do to solve that problem?

Thank you in advance!

[Cameron Wallace McKenzie]

Does each table have its own id field? This is where the join occurs.

I have three classes that participate in inheritance in my JOIN example, and you will notice that each has its own id field:




I have a little tutorial on mapping inheritance that you might find interesting. A Joined table mapping is provided as an example:

The Three Forms of Inheritance Mapping with Hibernate: A Simple Tutorial


Joined Table Inheritance

One of the ugly aspects of the TABLE_PER_CLASS inheritance type is the fact that properties get duplicated down the class hierarchy. For example, why should the child table declare columns of type id and nationality when they are already defined in the ancestor table? The JOINED inheritance type addresses this problem by having tables only maintain data that maps directly to the properties in the associated class. Subclasses are then linked to their inherited properties through common primary key fields in the tables, linking as UNION joins at runtime.

To use a JOIN for mapping inheritance, all we have to do is edit the @Inheritance annotation of the Ancestor class, and set the strategy attribute to InheritanceType.JOINED:

@Entity
@Inheritance(strategy=InheritanceType.JOINED)
public class Ancestor { ... }
When using a JOINED strategy for our problem domain, Hibernate expects three database tables, with each table mapping to the various properties defined in each class. The id field then forms a union between tables. So, if an Ancestor instance is saved, a record will be created in only the ancestor table, whereas if a Child instance is created, the fields of the instance will be saved in all three tables, with the records in each table associated, or joined, through a common value for the id field. In essence, the class hierarchy of an instance is JOINED together from all of the individual tables.

Goodl luck!

-Cameron McKenzie

[Peter Irmstadt]

thank you for your answer!

Unfortunalety this doesn't seem to help me. I added an ID to the fields, but this became only a unique ID of the tables of the subclasses.
I bought a hibernate book that says (translated from German): "Use @Inheritance to set the inheritance type to JOINED. There's no need for further settings or annotations in the subclasses. If you want to rename the id field that is used to join the child classes with the parent ones you can use "@PrimaryKeyJoinColumn" in front of the class".

But no matter if I use it or not, I still get the same error. Any other ideas where my mistake might be?

[Cameron Wallace McKenzie]

I feel I've been challenged.

What's your development environment and what version of Hibernate/JPA are you using? Maybe I'll give this a try on my own.

Regards,

-Cameron

[Peter Irmstadt]

thank you for your answer!

I am using

Eclipse 3.4.2

JBoss Seam 2.1.1.GA

Newest version of JBoss Tools

Java version 1.6.0_13

Hibernate 3.2.4.sp1

Hibernate EntityManager 3.2.1.GA

Hibernate Annotations 3.2.1.GA

JBoss AS 4.2.1.GA

Thank you in advance!

[Douglas Ferguson]

Did you ever figure this out?