@Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp)
     throws ServletException, IOException {
   ServletOutputStream os = resp.getOutputStream();
   Person[] persons = personService.getAll();
   os.println("<html><body>");
   os.println("<h2>Persons</h2>");
   os.println("<table>");
   os.println("<tr><th>Id</th><th>Name</th><th>URL</th></tr>");
   for (Person person : persons) {
     String url = (person.getUrl() == null) ? "" : person.getUrl();
     os.println(
         String.format(
             "<tr><td>%s</td><td>%s</td><td>%s</td></tr>", person.getId(), person.getName(), url));
   }
   os.println("</table>");
   os.println("<h2>Add Person</h2>");
   os.println("<form name='input' action='/personui' method='post'>");
   os.println("<table>");
   os.println("<tr><td>Id</td><td><input type='text' name='id'/></td></tr>");
   os.println("<tr><td>Name</td><td><input type='text' name='name'/></td></tr>");
   os.println("<tr><td>Homepage URL</td><td><input type='text' name='url'/></td></tr>");
   os.println("<tr><td colspan='2'><input type='submit' value='Add'/></td></tr>");
   os.println("</form>");
   os.println("</table>");
   os.println("</body></html>");
 }
 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp)
     throws ServletException, IOException {
   String id = req.getParameter("id");
   String name = req.getParameter("name");
   String url = req.getParameter("url");
   Person person = new Person();
   person.setId(id);
   person.setName(name);
   person.setUrl(url);
   personService.addPerson(person);
   resp.sendRedirect("/personui");
 }