then, when the user "pepsi1" sign in, I want that redirect to:
http://localhost:8080/portal/private/pepsi
Is  posssible this? how do it?

No, it's not possible for now and it has been addressed by https://jira.jboss.org/browse/GTNPORTAL-879. You could add more information that you need for that feature to the JIRA issue, so hopefully it will be available soon.

isn't so, how change the default URL after login? what configuration  file i must to edit?

It is not configurable for now too, but you can customize our login form and use a parameter initialURI to specify a URL which will be redirected to after login. For instance in your case, initialURI=/portal/private/pepsi.

in exo.portal.component.web.jar there is java class called PortalLoginController.java

Here is the code of function

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException
   {
      String username = req.getParameter("username");
      String password = req.getParameter("password");

      //
      if (username == null)
      {
         log.error("Tried to access the portal login controller without username provided");
         resp.sendError(HttpServletResponse.SC_BAD_REQUEST, "No username provided");
         return;
      }
      if (password == null)
      {
         log.error("Tried to access the portal login controller without password provided");
         resp.sendError(HttpServletResponse.SC_BAD_REQUEST, "No password provided");
         return;
      }

      //
      log.debug("Found username and password and set credentials in http session");
      Credentials credentials = new Credentials(username, password);
      req.getSession().setAttribute(InitiateLoginServlet.CREDENTIALS, credentials);

      // Obtain initial URI
      String uri = req.getParameter("initialURI");

      // otherwise compute one
      if (uri == null || uri.length() == 0)
      {
         uri = req.getContextPath() + "/private/classic";

          //You can insert your functional component, to control the redirection after login.

          //and overwrite the original PortalLoginController.java in web.xml

         log.debug("No initial URI found, will use default " + uri + " instead ");
      }
      else
      {
         log.debug("Found initial URI " + uri);
      }

      // if we do have a remember me
      String rememberme = req.getParameter("rememberme");
      if ("true".equals(rememberme))
      {
         boolean isRemember = "true".equals(req.getParameter(InitiateLoginServlet.COOKIE_NAME));
         if (isRemember)
         {
            //Create token
            AbstractTokenService tokenService = AbstractTokenService.getInstance(CookieTokenService.class);
            String cookieToken = tokenService.createToken(credentials);

            log.debug("Found a remember me request parameter, created a persistent token " + cookieToken + " for it and set it up " +
               "in the next response");
            Cookie cookie = new Cookie(InitiateLoginServlet.COOKIE_NAME, cookieToken);
            cookie.setPath(req.getContextPath());
            cookie.setMaxAge((int)tokenService.getValidityTime() / 1000);
            resp.addCookie(cookie);
         }
      }

      //
      resp.sendRedirect(uri);
   }