Using saveOrUpdate() in Hibernate creates new records instead of updating existing ones

I have a class User

class User { 
  int id;
  String name;
}

where id is native generator in User.hbm.xml and name is primary-key in DB.

In my database I saved some information about Users.

Than I want to connect with this information about User.

For example in my DB I have a row INSERT INTO User VALUES ('Bill');

Main.java

User bill = new User();
bill.setName("Bill");
session.saveOrUpdate(bill);

This code always tries to insert a new Bill row into the table rather than update the existing Bill row.