Servlet context is not working

Question

Please i am trying to store a player object in a HashTable which would then be stored in the ServletContext. When the class is called it is supposed to check if the player (object) is already in the playerList (HashTable) which is stored in the Servlet Context. But each time i call the class it shows that the player(object) isn't in the playerList (HashTable) so it creates a new Player object. I have tried including

this.getServletContext().setAttribute("playerList",playerList);
this.getServletConfig().getServletContext().setAttribute("playerList",playerList);

BUT it still is not working.

public class InitGameServlet extends HttpServlet {

    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException, JSONException {
        response.setContentType("text/plain;charset=UTF-8");
        PrintWriter out = response.getWriter();

        try {
            ServletContext context = getServletContext();
            Hashtable playerList = (Hashtable)context.getAttribute("playerList");
            String playerid=request.getParameter("id");
            HttpSession session=request.getSession(true);
            Player player=null;

            if(!playerList.contains(playerid)) {
                player=new Player(playerid,50);
                playerList.put(playerid, player);                           
                System.out.println("This player wasnt there before so i have put it");
            }
            else {
                player=(Player)playerList.get(playerid);
                System.out.println("This player was there so i have retreived it");
            }
        }
    }
}

@WebListener
public class InitializeGameContext implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        ServletContext context = sce.getServletContext();
        Hashtable<String, Game> gameList = new Hashtable();
        context.setAttribute("gameList", gameList);
        context.log("The game list has beeen loaded...............");
        Hashtable<String, Player> playerList = new Hashtable();
        context.setAttribute("playerList", playerList);
        context.log("The playerList list has beeen loaded..................");
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {

    }

}

In my web.xml i have

<listener>
    <listener-class>web.InitializeGameContext</listener-class>
</listener>

EDIT: My complete web.xml

<servlet>
    <servlet-name>InitGameServlet</servlet-name>
    <servlet-class>com.whot.servlet.InitGameServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>InitGameServlet</servlet-name>
    <url-pattern>/InitGameServlet</url-pattern>
</servlet-mapping>
<session-config>
    <session-timeout>
        3000
    </session-timeout>
</session-config>
<listener>
    <listener-class>web.InitializeGameContext</listener-class>
</listener>

Answer 1

Answer

Hashtable.contains() Tests if some key maps into the specified value in this hashtable.

So, within your Servlet at this line

if(!playerList.contains(playerid)) {

you're actually comparing a key (playerid) with all the values (Player objects) in your Hashtable. Hence, the match is failing every time.

Your ServletContext (as well as its listener) works fine since you're receiving your Hashtable (playerList) on every Servlet call correctly. So, to fix the problem use Hashtable.containsKey() which tests if an object mapping already exists for the specified key.

Other observations

• Its kind of a misnomer to call a Hashtable a list. Use playerMap as an identifier since the table maps a playerid kay to a Player value object.
  
  
• There's no need to both annotate the listener (with @WebListener) as well as configure it declaratively in web.xml (with <listener>). Use only one of the two approaches.
  
  
• Unlike HttpSession.setMaxInactiveInterval() (which sets timeout in secs) <session-timeout> sets the timeout interval in mins. So, if you wanted a default session length of 3 mins change 3000 to 3.