java - adding static property data when creating entities -

suppose have 2 entity types: user , country.

country entities never created , aren't mutable. they're keyed iso alpha3 country codes, e.g. "usa". reside in table country pk column id.

users have many-to-one mapping country w/ cascade = none. users reside in user table fk column country_id references country(id).

when creating new user might like:

user user = new user(); user.setcountry(em.find(country.class, "usa")); em.persist(user); 

i gather that's wasteful, though, since requires query against country first. noticed can this:

country usa = new country(); usa.setid("usa"); user user = new user(); user.setcountry(usa); em.persist(user); 

since cascade = "none" shouldn't need query country table; should insert "usa" directly user country_id. correct?

now suppose there's code ever creates users country_id = "usa". in case, occurred me store static instance of country id = "usa" , use every new user? example:

public class usauserfactory implements factory<user> {      private static final country usa = new country();     static { usa.setid("usa"); }      public user newinstance() {         user user = new user();         user.setcountry(usa);         return user;     } }  public someotherclass {      public void persistuser(entitymanager em, factory<user> uf, ...) {         user user = uf.newinstance();         // set other properties         em.persist(user);     } } 

assume persistuser() called concurrently multiple threads , within multiple persistence contexts.

my questions:

1. will persisting user entities mutate singleton "usa" country instance in way?

2. is inadvisable other reasons entirely?

the 2 classes above illustrate question; i'm not doing quite silly.

i more inclined try using cache read-only data reduce actual database calls. see here setting cache might help.