Java tutorial
/* * To change this license header, choose License Headers in Project Properties. * To change this template file, choose Tools | Templates * and open the template in the editor. */ package edu.utd.cs6301.shas.controller; import com.google.gson.ExclusionStrategy; import com.google.gson.FieldAttributes; import com.google.gson.Gson; import com.google.gson.GsonBuilder; import com.google.gson.JsonArray; import com.google.gson.JsonElement; import com.google.gson.reflect.TypeToken; import edu.utd.cs6301.shas.entity.Detector; import edu.utd.cs6301.shas.sessionbean.DetectorFacade; import java.io.IOException; import java.io.PrintWriter; import java.util.Collection; import java.util.List; import java.util.Set; import javax.ejb.EJB; import javax.servlet.AsyncContext; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * * @author Zheng */ @WebServlet(name = "DetectorServlet", loadOnStartup = 1, urlPatterns = { "/detector" }, asyncSupported = true) public class DetectorServlet extends HttpServlet { @EJB private DetectorFacade detectorBean; private Gson gson; public void init() throws ServletException { gson = new GsonBuilder().setExclusionStrategies(new ExclusionStrategy() { public boolean shouldSkipClass(Class<?> clazz) { return false; } /** * Custom field exclusion goes here */ public boolean shouldSkipField(FieldAttributes f) { return false; } }) /** * Use serializeNulls method if you want To serialize null * values By default, Gson does not serialize null values */ .serializeNulls().create(); } /** * Processes requests for both HTTP <code>GET</code> and <code>POST</code> * methods. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws IOException { if (request.getParameter("action") != null) { String action = (String) request.getParameter("action"); String responseStr = null; try { switch (action) { case "list": responseStr = displayDetector(request); break; case "create": responseStr = createDetector(request); break; case "update": responseStr = updateDetector(request); break; case "delete": responseStr = deleteDetector(request); break; } response.setContentType("application/json"); response.getWriter().print(responseStr); // System.out.println(">>> reponse has been sent out..."); // registerAsyncContext(request, response); // System.out.println(">>> process finished."); } catch (Exception ex) { String error = "{\"Result\":\"ERROR\",\"Message\":" + ex.getStackTrace() + "}"; response.getWriter().print(error); System.err.println(ex.getMessage()); } } } private void registerAsyncContext(HttpServletRequest request, HttpServletResponse response) { //register this servlet as a observer to show the event. AsyncContext aCtx = request.startAsync(request, response); Set<AsyncContext> eventObservers = (Set<AsyncContext>) request.getServletContext() .getAttribute("eventObserver"); System.out.println(">>>> " + eventObservers.size()); eventObservers.add(aCtx); request.getServletContext().setAttribute("eventObserver", eventObservers); } private String displayDetector(HttpServletRequest request) throws IOException { List<Detector> sprinklers = detectorBean.findAll(); String listData = gson.toJson(sprinklers); //Return Json in the format required by jTable plugin return "{\"Result\":\"OK\",\"Records\":" + listData + "}"; } private String createDetector(HttpServletRequest request) throws IOException { String id = request.getParameter("detectorid"); String des = request.getParameter("description"); String mode = request.getParameter("controlmode"); String status = request.getParameter("status"); Detector s = new Detector(); s.setDetectorid(id); s.setDescription(des); s.setStatus(status); detectorBean.create(s); String json = gson.toJson(s); return "{\"Result\":\"OK\",\"Record\":" + json + "}"; } private String deleteDetector(HttpServletRequest request) { Detector s = detectorBean.find(request.getParameter("detectorid")); detectorBean.remove(s); return "{\"Result\":\"OK\"}"; } private String updateDetector(HttpServletRequest request) { String id = request.getParameter("detectorid"); String des = request.getParameter("description"); String status = request.getParameter("status"); Detector s = new Detector(); s.setDetectorid(id); s.setDescription(des); s.setStatus(status); detectorBean.edit(s); String json = gson.toJson(s); // Return Json in the format required by jTable plugin return "{\"Result\":\"OK\",\"Record\":" + json + "}"; } // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code."> /** * Handles the HTTP <code>GET</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Handles the HTTP <code>POST</code> method. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } /** * Returns a short description of the servlet. * * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; }// </editor-fold> }