Hey I want to implement a Java Servlet that starts a thread only once for every single user. Even on refresh it should not start again. My last approach brought me some trouble so no code^^. Any Suggestions for the layout of the servlet?

 public class LoaderServlet extends HttpServlet {
// The thread to load the needed information
private LoaderThread loader;
// The last.fm account
private String lfmaccount;

public LoaderServlet() {
    super();
    lfmaccount = "";
}

@Override
protected void doPost(HttpServletRequest request,
        HttpServletResponse response) throws ServletException, IOException {
    if (loader != null) {
        response.setContentType("text/plain");
        response.setHeader("Cache-Control", "no-cache");
        PrintWriter out = response.getWriter();
        out.write(loader.getStatus());
        out.flush();
        out.close();
    } else {
        loader = new LoaderThread(lfmaccount);
        loader.start();
        request.getRequestDispatcher("WEB-INF/pages/loader.jsp").forward(
                request, response);
    }
}

@Override
protected void doGet(HttpServletRequest request,
        HttpServletResponse response) throws ServletException, IOException {
    if (lfmaccount.isEmpty()) {
        lfmaccount = request.getSession().getAttribute("lfmUser")
                .toString();
    }
    request.getRequestDispatcher("WEB-INF/pages/loader.jsp").forward(
            request, response);
}
}

The jsp uses ajax to regularly post to the servlet and get the status. The thread just runs like 3 minutes, crawling some last.fm data.