code: public void setCredential(String username, String password) {
  	if (username != null) {
  	    env.put("java.naming.security.principal", username);
  	    env.put("java.naming.security.credentials", password);
  	}
  	else {
  	    env.remove("java.naming.security.principal");
  	    env.remove("java.naming.security.credentials");
  	}
      }
docs: sets username password for the connection
  
  @param username
  @param password