Database view with no notion of primary key as @entity using EclipseLink 2.5.x, JPA 2.0

gistfile1.txt

Hi Adam,
We read data from a database view. This view has no database-side notion of primary key, but the columns (MyView.a, MyView.b, MyView.c) uniquelly identify a record. The columns MyView.a and MyView.b can contain NULL values.

My Java entity class looks like this:

@Entity
@PrimaryKey(validation=IdValidation.NONE, columns={@column(name="a"), @column(name="b", @column(name="c")})
public class MyView implements Serializable ......

If I run the query (as JUnit test) then I will receive the following error message:

Exception [EclipseLink-6044] (Eclipse Persistence Services - 2.5.1. .....
org.eclipse.persistence.exceptions.QueryException Exception Description: The primary key read from the row [row omitted here] during the execution of the query was detected to be null. Primary keys must not contain null. 

Questions:
- What do I make wrong?
- Is it a problem that I define EclipseLink as JPA provider in persistence.xml file BUT using EclipseLink extensions, e.g. @PrimaryKey. Is this ignored?
- How persistence.xml should look like in generall?

Thanks for the answers.
Jan