Use different field for column in subclass of EJB entity - jpa

Question

I need some help with the design of my entities.
I have a single table MyEntity with the following columns:
id | column1 | column2 | type
And the entity looks like:
#Entity
#DiscriminatorColumn(discriminatorType = DiscriminatorType.STRING, name = "type", length = 255)
#Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class MyEntity {
#id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
}
I would like to be able to have several entities inheriting from MyEntity and where each entity define how they use the columns column1 and column2. I would like to just use one single table for all my subclasses, and use the discriminator.
Like this (the following doesn't work):
#Entity
#DiscriminatorValue("TestClass1")
public class TestClass1 extends MyEntity {
#Column(name = "column1");
private long testField1;
#Column(name = "column2");
private long testField2;
}
#Entity
#DiscriminatorValue("TestClass2")
public class TestClass2 extends MyEntity {
#Column(name = "column1");
private long anotherName1;
#Column(name = "column2");
private long anotherName2;
}
I know this approach is not working, so I am reaching out to you guys for help.
EDIT
I have added the inheritance strategy to the MyEntity class, but SINGLE_TABLE is default, so it shouldn't make a difference.
I have tried two approaches:
1) If I don't put two fields MyEntity named column1 and column2, then I cannot create any named queries in MyEntity such as:
#NamedQuery(name=TEST, query="select m from MyEntity m where m.column1 = :val")
I get the following exception:
Caused by: org.hibernate.QueryException: could not resolve property: column1 of: com.test.MyEntity
I would really prefer to specify the queries in MyEntity and not in the subclasses.
2) If I put the fields (column1 and column2) in MyEntity, then I get the following exception:
Caused by: org.hibernate.MappingException: Repeated column in mapping for entity: com.test.TestClass1 column: column1 (should be mapped with insert="false" update="false")
and I don't know how to move on from here. I'm not sure how to do the mapping, which is suggested in the exception message.