WebSphere Applcation Server - how to get J2C authentication alias in Java code

Sometimes I need securely connect to external system from WebSphere Application server application. The secure connection usualy requires password as a credential. The WebSphere Application Server allows store the username and password inside its configuration as so called J2C Authentication Alias. If I need use the cofigured J2C Auth Alias I can use the following Java code fragment:

 public static final String USERNAME = "username";
 public static final String PASSWORD = "password";

 /** Return username and pasword for specific J2C authentication alias
  *
  * @param authenticationAlias
  * @return Map with "username" and "password" keys
  * @throws NotImplementedException
  * @throws LoginException
  */
      public Map<String,String> getCredentials(String authenticationAlias) throws NotImplementedException, LoginException {
     Map<String,String> map = new HashMap<String,String>();
     map.put(Constants.MAPPING_ALIAS, authenticationAlias);
     CallbackHandler callbackHandler = WSMappingCallbackHandlerFactory.getInstance().getCallbackHandler(map, null);
     LoginContext loginContext = new LoginContext("DefaultPrincipalMapping", callbackHandler);
     loginContext.login();
     Subject subject = loginContext.getSubject();
     Set credentials = subject.getPrivateCredentials();
     PasswordCredential passwordCredential = (PasswordCredential) credentials.iterator().next();
     String user = passwordCredential.getUserName();
     String password = new String(passwordCredential.getPassword());
     Map<String,String> result = new HashMap<String,String>();
     result.put(USERNAME, user);
     result.put(PASSWORD, password);
     return result;
      }