DAO pattern with Factory Method

gistfile1.java

public interface GenericDao<T, K> {
	public K insert(T object);
}

public class GenericDaoMongoDBImpl<T, K> implements GenericDao<T, K> {
	public K insert(T object) {
		return null;
	}
}

public interface ObjectDao extends GenericDao<Object, ObjectId> {
}

public class ObjectDaoMongoDBImpl extends GenericDaoMongoDBImpl<Object, ObjectId> implements ObjectDao {
}

public class DaoFactory {
	public static GenericDao<Object, ObjectId> createDao() {
		return new ObjectDaoMongoDBImpl();
	}
}