Being a Web App: attributes and listeners(Head First Servlets and JSP)
MyServletContextListener
1 package com.example;
2
3 import javax.servlet.*;;
4
5 public class MyServletContextListener implements ServletContextListener
6 {
7 public void contextInitialized(ServletContextEvent event)
8 {
9 ServletContext sc = event.getServletContext();
10 String dogBreed = sc.getInitParameter("breed");
11 Dog d = new Dog(dogBreed);
12 sc.setAttribute("dog",d);
13 }
14
15 public void contextDestroyed(ServletContextEvent event)
16 {
17
18 }
19 }
2
3 import javax.servlet.*;;
4
5 public class MyServletContextListener implements ServletContextListener
6 {
7 public void contextInitialized(ServletContextEvent event)
8 {
9 ServletContext sc = event.getServletContext();
10 String dogBreed = sc.getInitParameter("breed");
11 Dog d = new Dog(dogBreed);
12 sc.setAttribute("dog",d);
13 }
14
15 public void contextDestroyed(ServletContextEvent event)
16 {
17
18 }
19 }
ListenerTester
1 package com.example;
2
3 import javax.servlet.*;
4 import javax.servlet.http.*;
5 import java.io.*;
6
7 public class ListenerTester extends HttpServlet {
8 public void doGet (HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
9 response.setContentType("text/html");
10 PrintWriter out = response.getWriter();
11 out.println("test context attributes set by listener<br>"); out.println("<br>");
12 Dog dog = (Dog) getServletContext().getAttribute("dog");
13 out.println("Dog’s breed is: " + dog.getBreed());
14 }
15 }
16
2
3 import javax.servlet.*;
4 import javax.servlet.http.*;
5 import java.io.*;
6
7 public class ListenerTester extends HttpServlet {
8 public void doGet (HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
9 response.setContentType("text/html");
10 PrintWriter out = response.getWriter();
11 out.println("test context attributes set by listener<br>"); out.println("<br>");
12 Dog dog = (Dog) getServletContext().getAttribute("dog");
13 out.println("Dog’s breed is: " + dog.getBreed());
14 }
15 }
16
1 package com.example;
3 public class Dog
4 {
5 private String breed;
6
7 public Dog(String breed)
8 {
9 this.breed = breed;
10 }
11
12 public String getBreed()
13 {
14 return breed;
15 }
16 }
17
3 public class Dog
4 {
5 private String breed;
6
7 public Dog(String breed)
8 {
9 this.breed = breed;
10 }
11
12 public String getBreed()
13 {
14 return breed;
15 }
16 }
17