Consider the following situation: we have two entities with a common superclass:

public abstract class Parent
{
private String name;

public String getName()
{
return this.name;
}

public void setName(String name)
{
this.name = name;
}
}

public class FirstAncestor extends Parent
{
//some string property with getter and setter
}

public class SecondAncestor extends Parent
{
//this class have no it's own properties, only the parent's ones. IMPORTANT: ID of that class should be mapped to "parent" table (see below).
}

And a following DB structure, schematically:

parentsTable(parent_id(primary key), name)
firstAncestorsTable(first_ancestor_id(primary key), parent_id(foreign key references to parentsTable.parent_id), [some other fields])

I'd like to be FirstAncestor class to be mapped to firstAncestors table, FirstAncestor id should be mapped to first_ancestor_id;
SecondAncestor shouln't be mapped to a table directly, but it should take it's ID from parentsTable and it's other fields too. Is it possible to do such a thing? Sorry for my english, it's a foreign language to me.

What you want is a single-table inheritance structure.

You can take something like this:


And map it to a single table like this:



@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
public class Ancestor { }

Here's a little tutorial on the subject:

http://jpa.ezhibernate.com/Javacode/lea ... ncewithjpa