code: package playlist.controller;
  
  import playlist.model.PlaylistDAO;
  import playlist.model.StatisticsDAO;
  import playlist.model.UserDAO;
  
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import javax.servlet.http.HttpSession;
  import java.io.IOException;
  
  /**
   * DataStax Academy Sample Application
   *
   * Copyright 2013 DataStax
   *
   */
  
  public class PlaylistsServlet extends HttpServlet {
  
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       doAction(request, response);
    }
  
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       doAction(request, response);
    }
  
    private void doAction(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      HttpSession httpSession = request.getSession(true);
      UserDAO user = (UserDAO) httpSession.getAttribute("user");
  
      // If we're not logged in, go to the login page
      if (user == null) {
  
        request.setAttribute("error", "Not Logged In");
        response.sendRedirect("login");
        return;
  
      }
  
      UserDAO userFromDB = UserDAO.getUser(user.getUsername());
  
      String button = request.getParameter("button");
      String playlist = request.getParameter("pl");
  
  
      if (button != null) {
        if (button.contentEquals("deletePlaylist")) {
  
          // Delete the playlist
          new PlaylistDAO(user.getUsername(), playlist).deletePlayList();
  
          // Force a re-read in this case
          response.sendRedirect("playlists");
          return;
  
        } else if (button.contentEquals("Add")) {
          if (playlist != null) {
            doAddPlaylist(userFromDB, playlist);
          }
        }
      }
  
      request.setAttribute("username", userFromDB.getUsername());
      request.setAttribute("playlist_names", userFromDB.getPlaylist_names());
      getServletContext().getRequestDispatcher("/playlists.jsp").forward(request,response);
  
    }
  
    private void doAddPlaylist(UserDAO user, String playlistName) {
  
      StatisticsDAO.increment_counter("playlists");
  
      PlaylistDAO.createPlayList(user, playlistName);
    }
  
  }
  