Membuat Servlet Context dan Listener Database di Java Servlet

assalamualaikum kawan-kawan :)

postingan ini adalah lanjutan yang sebelumnya tentang Servlet Filter, kali ini saya akan sharing tentang program Java Servlet Context dan Listener Database. Langsung aja kita buat programnya

pertama kita buat index.html

    
        
        
    
    
        servlet context dan Listener
    

kemudian kita buat class bernama DBConnectionManager.java
source codenya sebagai berikut :

import java.sql.Connection;
/**
 *
 * @author Ilyas A. Jaelani
 */
public class DBConnectionManager {
    private String dbURL;
    private String user;
    private String password;
    private Connection con;
    
    public DBConnectionManager(String url, String u, String p) {
        this.dbURL = url;
        this.user = u;
        this.password = p;
//create db connection now
    }
    public Connection getConnection() {
        return this.con;
    }

    public void closeConnection() {
//close DB connection here
    }   
}

buat file servlet MyServlet.java
source codenya sebagai berikut :

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 *
 * @author Ilyas A. Jaelani
 */
public class MyServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * Processes requests for both HTTP
     * GET and
     * POST 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");
        PrintWriter out = response.getWriter();
        try {
            /* TODO output your page here. You may use following sample code. */
            out.println("");
            out.println("");
            out.println("");
            out.println("");            
            out.println("");
            out.println("");
            out.println("

Servlet MyServlet at " + request.getContextPath() + "
");
            out.println("");
            out.println("");
        } finally {            
            out.close();
        }
    }

    // 
    /**
     * Handles the HTTP
     * GET 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);
        ServletContext ctx = request.getServletContext();
        ctx.setAttribute("User", "Ilyas");
        String user = (String) ctx.getAttribute("User");
        ctx.removeAttribute("User");

        HttpSession session = request.getSession();
        session.invalidate();

        PrintWriter out = response.getWriter();
        out.write("Hi " + user);

    }

    /**
     * Handles the HTTP
     * POST 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";
    }// 
}

Tambahkan  file  listener  baru  dengan  nama AppContextListener.java. Ikuti  langkah sebagai berikut :

source codenya sebagai berikut :

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 * Web application lifecycle listener.
 *
 * @author Ilyas A. Jaelani
 */
public class AppContextListener implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        ServletContext ctx = sce.getServletContext();

        String url = ctx.getInitParameter("DBURL");
        String u = ctx.getInitParameter("DBUSER");
        String p = ctx.getInitParameter("DBPWD");

        //create database connection from init parameters and set it to context
        DBConnectionManager dbManager = new DBConnectionManager(url, u, p);
        ctx.setAttribute("DBManager", dbManager);
        System.out.println("Database connection initialized for Application.");
        
//        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        ServletContext ctx = sce.getServletContext();
        DBConnectionManager dbManager = (DBConnectionManager) ctx.getAttribute("DBManager");
        dbManager.closeConnection();
        System.out.println("Database connection closed for Application.");
    
//        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
}

Tambahkan  file  listener  baru  dengan  nama AppContextAttributeListener.java.

source codenya sebagai berikut :

import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 * Web application lifecycle listener.
 *
 * @author Ilyas A. Jaelani
 */
public class AppContextAttributeListener implements ServletContextAttributeListener {

    @Override
    public void attributeAdded(ServletContextAttributeEvent event) {
        System.out.println("ServletContext attribute added::{" + event.getName() +"," + event.getValue() + "}");
    
//        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

    @Override
    public void attributeRemoved(ServletContextAttributeEvent event) {
                System.out.println("ServletContext attribute replaced::{" + event.getName() + "," + event.getValue() + "}");

//        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

    @Override
    public void attributeReplaced(ServletContextAttributeEvent event) {
        System.out.println("ServletContext attribute removed::{" + event.getName() + "," + event.getValue() + "}");
 
//        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
}

Tambahkan  file  listener  baru  dengan  nama MySessionListener.java.

source codenya sebagai berikut :

import javax.servlet.http.HttpSessionEvent;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 * Web application lifecycle listener.
 *
 * @author Ilyas A. Jaelani
 */
public class MySessionListener implements javax.servlet.http.HttpSessionListener {

    @Override
    public void sessionCreated(HttpSessionEvent se) {
        System.out.println("Session Created:: ID=" + se.getSession().getId());
//        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent se) {
        System.out.println("Session Destroyed:: ID=" + se.getSession().getId());
//        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
}

Tambahkan  file  listener  baru  dengan  nama MyServletRequestListener.java.

source codenya sebagai berikut :

import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequest;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 * Web application lifecycle listener.
 *
 * @author Ilyas A. Jaelani
 */
public class MyServletRequestListener implements javax.servlet.ServletRequestListener {

    @Override
    public void requestDestroyed(ServletRequestEvent sre) {
        ServletRequest servletRequest = sre.getServletRequest();
        System.out.println("ServletRequest destroyed. Remote IP=" +
servletRequest.getRemoteAddr());
//        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

    @Override
    public void requestInitialized(ServletRequestEvent sre) {
        ServletRequest servletRequest = sre.getServletRequest();
        System.out.println("ServletRequest initialized. Remote IP=" + servletRequest.getRemoteAddr());
    
//        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
}