ServletContext dan Listener DB

Buat lah sebuah project web application menggunakan netbeans. Kemudian beri nama ServletListener. Adapun struktur program nya seperti berikut ini :

DBConnectionManager.java

import java.sql.Connection;

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
    }
}

MyServlet.java

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;


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");
        try (PrintWriter out = response.getWriter()) {
            /* 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("");
        }
    }

    // 
    /**
     * 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", "Firman Sari");
        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";
    }// 

}

AppContextListener.java

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

/*
 * 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.
 */
/**
 * Web application lifecycle listener.
 *
 * @author Azie
 */
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.");
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        ServletContext ctx = sce.getServletContext();
        DBConnectionManager dbManager = (DBConnectionManager) ctx.getAttribute("DBManager");
        System.out.println("Database connection closed for application.");
    }
}

AppContextAttributeListener.java

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

/*
 * 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.
 */
/**
 * Web application lifecycle listener.
 *
 */
public class AppContextAttributeListener implements ServletContextAttributeListener {

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

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

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

MySessionListener.java

import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

/*
 * 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.
 */
/**
 * Web application lifecycle listener.
 *
 */
public class MySessionListener implements HttpSessionListener {

    @Override
    public void sessionCreated(HttpSessionEvent se) {
        System.out.println("Session Created:: ID=" + se.getSession().getId());
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent se) {
        System.out.println("Session Destroyed:: ID=" + se.getSession().getId());
    }
}

MyServletRequestListener.java

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

/*
 * 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.
 */
/**
 * Web application lifecycle listener.
 *
 */
public class MyServletRequestListener implements ServletRequestListener {

    @Override
    public void requestDestroyed(ServletRequestEvent sre) {
        ServletRequest servletRequest = sre.getServletRequest();
        System.out.println("ServletRequest destroyed. Remote IP=" + servletRequest.getRemoteAddr());
    }

    @Override
    public void requestInitialized(ServletRequestEvent sre) {
        ServletRequest servletRequest = sre.getServletRequest();
        System.out.println("ServletRequest initialized. Remote IP=" + servletRequest.getRemoteAddr());
    }
}