code: @Override
      public Subject performLogin(String jaasEntryName, CallbackHandler callbackHandler, Subject partialSubject) throws LoginException {
          LoginContext loginContext = null;
          loginContext = doLoginContext(jaasEntryName, callbackHandler, partialSubject);
          return (loginContext == null ? null : loginContext.getSubject());
      }
docs: Performs a JAAS login.
  
  @param jaasEntryName
  @param callbackHandler
  @param partialSubject
  @return the authenticated subject.
  @throws javax.security.auth.login.LoginException