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. */ import java.io.IOException; import java.io.PrintWriter; import java.sql.*; import java.lang.*; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import org.json.JSONObject; //importing required JSON libraries import org.json.JSONArray; import org.json.JSONException; /** * * @author Ishtiaq */ @WebServlet(name = "fetchBooks", urlPatterns = { "/fetchBooks" }) public class fetchBooks extends HttpServlet { /** * 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 ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); try (PrintWriter out = response.getWriter()) { /* TODO output your page here. You may use following sample code. */ out.println("<!DOCTYPE html>"); out.println("<html>"); out.println("<head>"); out.println("<title>Servlet fetchBooks</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>Servlet fetchBooks at " + request.getContextPath() + "</h1>"); out.println("</body>"); out.println("</html>"); } } // <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); try { System.out.println("Inside try 1"); Class.forName("org.apache.derby.jdbc.ClientDriver").newInstance(); //setting up the connection String dbURL = "jdbc:derby://localhost:1527/autolib_db_test"; Connection conn = DriverManager.getConnection(dbURL, "ishtiaq", "ishtiaq"); Statement stmt = null; ResultSet rslt = null; if (conn == null) { System.out.println("Connection Failed"); } stmt = conn.createStatement(); String searchTopic = request.getParameter("topic"); //running a select query in the underlying database on table named books_tbl. System.out.println("SEARCH TOPIC " + searchTopic); String sqlQry = "SELECT * FROM books_tbl where topic = '" + searchTopic.toUpperCase() + "'"; rslt = stmt.executeQuery(sqlQry); //query is executed by the statement. JSONObject jObj = new JSONObject(); //new jsonobject is created JSONArray bookArr = new JSONArray(); //new json array is created JSONObject book; try { System.out.println("Inside Try"); while (rslt.next()) { book = new JSONObject(); book.put("id", rslt.getInt("id")); //put the id of the book converted into Integer in "id" book.put("name", rslt.getString("bookname")); //put the bookname into "name" bookArr.put(book); //bookArr[] is inserted with book ID and bookname which are mandatory fields. } jObj.put("Books", bookArr); //maps bookArr content to String name "Books" } catch (JSONException jse) { } response.setContentType("application/json"); response.getWriter().write(jObj.toString()); //toString confirms to JSON syntax rules and converts the jObj content to json text. //System.out.println("after json"); if (!stmt.isClosed()) stmt.close(); //closing connection if (!rslt.isClosed()) rslt.close(); } catch (Exception e) { //return null; } } /** * Returns a short description of the servlet. * * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; }// </editor-fold> }