ADP- Chapter 3 Implementing Inter-Servlet Communication

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Riza Muhammad Nurman ADP
Chapter 3
on
Advanced Programming
FACULTY
Riza Muhammad Nurman
Implementing Inter-Servlet Communication

Content
• Implement the request dispatcher mechanism
• Work with filters

Navigation Between Servlets
Validation
Servlet
Is the
User
Valid?
NoYes
Welcome
Servlet
Error
Servlet

Dispatching a Request
• RequestDispatcher is an object of the
javax.servlet.RequestDispatcher interface that allows inter-servlet
communication
• Once you obtain the RequestDispatcher object, you can perform the
following tasks:
– Forward request to another Web page
– Include content of the calling Web page in the called Web page
RequestDispatcher dispatch = request.getRequestDispatcher("/WelcomeServlet");
dispatch.forward(request, response);

Implementasi
Login.java
Login.java
LoginServlet.java
Welcome.java
VALID
INVALID

Kode HTML untuk login
1. <html>
2. <head>
3. <title>TODO supply a title</title>
4. <meta charset="UTF-8">
5. <meta name="viewport" content="width=device-width, initial-scale=1.0">
6. <link rel="stylesheet" type="text/css" href="./css/style.css" />
7. </head>
8. <body>
9. <form name="formLogin" method="POST" action="LoginServlet" >
10. <h1>Login</h1>
11. <label><span>User ID: </span> <input type="text" id="userid" name="userid"/></label>
12. <label><span>Password: </span><input type="password" id="pass" name="pass"/></label>
13. <label>
14. <span> </span>
15. <input type="submit" value="Log In" class="button"/><input type="reset" value="Reset"
class="reset"/>
16. </label>
17. </form>
18. </body>
19. </html>

Kode HTML login dalam Servlet
1. protected void processRequest(HttpServletRequest request, HttpServletResponse response)
2. throws ServletException, IOException {
3. response.setContentType("text/html;charset=UTF-8");
4. try (PrintWriter out = response.getWriter()) {
5. out.println("<!DOCTYPE html>");
6. out.println("<html>");
7. out.println("<head>");
8. out.println("<title>Servlet Login</title>");
9. out.println("</head>");
10. out.println("<body>");
11. out.println("<form name='formLogin' method='POST' action='LoginServlet'");
12. out.println("<h1>Login</h1>");
13. out.println("<label><span>User ID: </span> <input type='text' id='userid' name='userid'/></label>");
14. out.println("<label><span>Password: </span><input type='password' id='pass'
name='pass'/></label>");
15. out.println("<label>");
16. out.println(" <span> </span>");
17. out.println(" <input type='submit' value='Log In'/><input type='reset' value='Reset'/>");
18. out.println("</label>");
19. out.println("</form>");
20. out.println("</body>");
21. out.println("</html>");
22. }
23. }

Code Snippet LoginServlet
1. protected void processRequest(HttpServletRequest request, HttpServletResponse
response)
5. String userid = request.getParameter("userid");
6. String password = request.getParameter("pass");
7.
8. if(userid.equals("admin") && password.equals("adminjuga")) {
9. RequestDispatcher dispatch = request.getRequestDispatcher("/Welcome");
10. dispatch.forward(request, response);
11. }
12. else {
13. RequestDispatcher dispatch = request.getRequestDispatcher("/Login");
14. dispatch.include(request, response);
15. out.println("Login Salah");
16. }
17. }
18. }

Welcome Servlet
response)
5. /* TODO output your page here. You may use following sample code. */
9. out.println("<title>Servlet Welcome</title>");
12. out.println("<h1>WELCOME</h1>");
15. }
16. }

Transferring Data
1. * ketik : import javax.servlet.RequestDispatcher; di atas nama class
response)
6. String userid = request.getParameter("userid");
7. String password = request.getParameter("pass");
8.
9. if(userid.equals("admin") && password.equals("adminjuga")) {
10. RequestDispatcher dispatch = request.getRequestDispatcher("/Welcome");
12. }
13. else {
14. request.setAttribute("result", "Login Salah");
15. RequestDispatcher dispatch = request.getRequestDispatcher("/Login");
17. }
18. }
19. }

Transferring Data 2
1. protected void processRequest(HttpServletRequest request, HttpServletResponse response)
8. out.println("<title>Servlet Login</title>");
11. out.println("<form name='formLogin' method='POST' action='LoginServlet'");
12. out.println("<h1>Login</h1>");
13. out.println("<label><span>User ID: </span> <input type='text' id='userid' name='userid'/></label>");
14. out.println("<label><span>Password: </span><input type='password' id='pass' name='pass'/></label>");
15. out.println("<label>");
16. out.println(" <span> </span>");
17. out.println(" <input type='submit' value='Log In'/><input type='reset' value='Reset'/>");
18. out.println("</label>");
19. out.println("</form>");
20. String data = (String)request.getAttribute("result");
21. if(data != null)
22. out.println(data);
25. }
26. }

Work With Filters
• Users use different types of client devices, such as desktops, laptops,
tablets, or mobile phone to access the Web applications stored in an
application server
• Each device displays the information in the application according to
the settings in the corresponding Web browser window
• Using servlet filters, you can customize the output of the application
so that it can be viewed in different browsers.
ServletServlet
Servlet
Client
Filter
Request Request
Response Response

User Interface On Client Devices
The Interface of KASKUS on the Desktop System
The Interface of KASKUS on the Mobile Phone Screen

Introduction to Filters
• A filter is an object that intercepts the requests and responses that
flow between a client and a servlet
– A filter can modify the headers and contents of a request coming from a Web
client and forward it to the target servlet
– A filter can also intercept and manipulate the headers and contents of the
response that is sent back by the servlet

IPFilter
1. public class IPFilter implements Filter {
2. String invalidip;
3. …
4. public IPFilter() {
5. }
6.
7. private void doBeforeProcessing(ServletRequest request,
ServletResponse response)
8. throws IOException, ServletException {
9. …
10. }
11. private void doAfterProcessing(ServletRequest request, ServletResponse
response)
12. throws IOException, ServletException {
13. ….
14. }

IPFilter 2
1. public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
2. if (debug) { log("IPFilter:doFilter()"); }
3. doBeforeProcessing(request, response);
4. Throwable problem = null;
5. try {
6. InetAddress ip = InetAddress.getLocalHost();
7. String addressIP = ip.getHostAddress();
8. if(addressIP.equals(this.invalidip)) {
9. RequestDispatcher rd = request.getRequestDispatcher("Error");
10. rd.forward(request, response);
11. }
12. else {
13. RequestDispatcher rd = request.getRequestDispatcher("Welcome");
14. rd.forward(request, response);
15. }
16. chain.doFilter(request, response);
17. } catch (Throwable t) {
18. problem = t;
19. t.printStackTrace();
20. }
21. doAfterProcessing(request, response);
22. ….
23. }

Output Program

ADP- Chapter 3 Implementing Inter-Servlet Communication

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