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3 – Web applications: Server-side code (JSP)

3 – Web applications: Server-side code (JSP). Admin: On-line Quiz. Useful, but limited multiple choice, same concepts actual tests are free text. Session Aims & Objectives. Aims To introduce the fundamental ideas involved in server-side code

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3 – Web applications: Server-side code (JSP)

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  1. 3 – Web applications:Server-side code (JSP)

  2. Admin: On-line Quiz • Useful, but limited • multiple choice, same concepts • actual tests are free text

  3. Session Aims & Objectives • Aims • To introduce the fundamental ideas involved in server-side code • Objectives,by end of this week’s sessions, you should be able to: • create a JSP web-page, including: • HTML, • server-side Java (JSP), and • JavaScript

  4. Example: Logon (analysis) • SPECIFICATION • User Requirements • protection from fraud and invasion of privacy • Software Requirements • Functional: • logon page, user must type name and password • following pages can only be accessed after successful logon • Non-functionalshould be very difficult to hack • hotmail, Amazon, University portal, utility bills (gas, electricity, phone, internet), Travel (flights, ferry, car rental)

  5. Example: Logon (design) • Restrict access tohome page

  6. Example: Logon (code v1) Logon.htm • Using Client-side JavaScript <html> <head><title></title></head> <body> Please logon:<br /> <input id="txtUserName" type="text" /><br /> <input id="txtPassWord" type="text" /><br /> <input id="btnLogon" type="submit" value="Logon" onclick="btnLogon_onClick()" /> <p id="msg"></p> </body> </html> <script language="javascript"> function btnLogon_onClick(){ var un; var pw; un = txtUserName.value; pw = txtPassWord.value; if(un == "mark" && pw == "soft131"){ window.navigate("home.htm"); }else{ msg.innerText = "Login details incorrect."; } } </script> Home.htm <html> <head><title>My Home page</title></head> <body> <p> Welcome to my home page.<br /> <img src="YouAreHere.jpg" /> </p> </body> </html>

  7. Example: Login (Problem) • View Source – shows client-side script: Reveals bothusername & password

  8. Web Hardware and Software network connection Client Server Browser Application (MS Explorer, FireFox, Opera) Web-server Application (MS IIS, Apache)

  9. Request-Response Cycle Request Web-server Application (MS IIS, Apache) Browser Application (MS Explorer, Firefox) Logon.htm Response <html> <head><title></title></head> <body> Please logon:<br /> <input id="txtUserName" type="text" /><br /> <input id="txtPassWord" type="text" /><br /> <input id="btnLogon" type="submit" value="Logon" onclick="btnLogon_onClick()" /> <p id="msg"></p> </body> </html> <script language="javascript"> function btnLogon_onClick(){ var un; var pw; un = txtUserName.value; pw = txtPassWord.value; if(un == "mark" && pw == "soft131"){ window.navigate("home.htm"); }else{ msg.innerText = "Login details incorrect."; } } </script> Client-side code:Code sent to Client Interpreted by browser

  10. Server-Side Technology • Microsoft • Active Server Pages (ASP) = VBScript • ASP.NET = VB.NET or C# • Sun • Java Server Pages (JSP) = Java • PhP • Perl / CGI

  11. Server-side Script (what) • JSP – active server pages • code not sent to client • code secure (can't be viewed by client) • executed on server • takes time – request-response cycle • requires server software (e.g. Apache) • JSP pages will NOT work by double clicking on file

  12. Example: Date date.jsp <%@page import="java.util.Date" %> <%@page import="java.text.SimpleDateFormat" %> <% Date today; SimpleDateFormat formatD; SimpleDateFormat formatT; String d; String t; today = new Date(); formatD = new SimpleDateFormat("EEE dd MM yyyy"); formatT = new SimpleDateFormat("HH:mm:ss"); d = formatD.format(today); t = formatT.format(today); %> <!DOCTYPE html> <html> <head><title>Date</title></head> <body> The date today is <%=d%><br /> The time is <%=t%> </body> </html> • JSP page: • .jsp (not .htm) • Scriptlet tag <% • variables have type • Date() is current date and time (on server) • Expression tag <%=

  13. Request-Response Cycle Request date.jsp Browser Application (MS Explorer, Firefox) Web-server Application (MS IIS, Apache) <%@page import="java.util.Date" %> <%@page import="java.text.SimpleDateFormat" %> <% Date today; SimpleDateFormat formatD; SimpleDateFormat formatT; String d; String t; today = new Date(); formatD = new SimpleDateFormat("EEE dd MM yyyy"); formatT = new SimpleDateFormat("HH:mm:ss"); d = formatD.format(today); t = formatT.format(today); %> <!DOCTYPE html> <html> <head><title>Date</title></head> <body> The date today is <%=d%><br /> The time is <%=t%> </body> </html> Response <!DOCTYPE html> <html> <head><title>Date</title></head> <body> The date today is Tue 11 10 2011<br /> The time is 14:21:41 </body> </html> Server-side code: run on server(never sent to Client)

  14. View Source • Code executed at server • code is never sent to client • View, Source – does not show code:

  15. Example: AddNum (client-side) AddNum.htm <html> <head><title></title></head> <body> <input id="txtN1" type="text" /><br /> <input id="txtN2" type="text" /><br /> <input id="btnAdd" type="submit" value="Add" onclick="btnAdd_onClick()" /> <p id="parRes"></p> </body> </html> <script language="javascript"> function btnAdd_onClick(){ var N1; var N2; N1 = parseFloat(txtN1.value); N2 = parseFloat(txtN2.value); parRes.innerText = N1 + N2; } </script>

  16. Example: AddNum (server-side) AddNum.jsp • check button click • request.getParametergets data from form • input tags inside form • use name (not id) • submit button:refreshes page (sending data to server) <%@page contentType="text/html" pageEncoding="UTF-8"%> <% double N1; double N2; String Res = ""; if (request.getParameter("btnAdd") != null){ N1 = Double.parseDouble(request.getParameter("txtN1")); N2 = Double.parseDouble(request.getParameter("txtN2")); Res = Double.toString(N1 + N2); } %> <!DOCTYPE html> <html> <head><title>Add Numbers</title></head> <body> <form method="post"> <input name="txtN1" type="text" /><br /> <input name="txtN2" type="text" /><br /> <input name="btnAdd" type="submit" value="Add" /> <p><%=Res%></p> </form> </body> </html>

  17. Client-side vs. Server-side Code AddNum.htm AddNum.jsp <html> <head><title></title></head> <body> <input id="txtN1" type="text" /><br /> <input id="txtN2" type="text" /><br /> <input id="btnAdd" type="submit" value="Add" onclick="btnAdd_onClick()" /> <p id="parRes"></p> </body> </html> <script language="javascript"> function btnAdd_onClick(){ var N1; var N2; N1 = parseFloat(txtN1.value); N2 = parseFloat(txtN2.value); parRes.innerText = N1 + N2; } </script> <%@page contentType="text/html" pageEncoding="UTF-8"%> <% double N1; double N2; String Res = ""; if (request.getParameter("btnAdd") != null){ N1 = Double.parseDouble(request.getParameter("txtN1")); N2 = Double.parseDouble(request.getParameter("txtN2")); Res = Double.toString(N1 + N2); } %> <!DOCTYPE html> <html> <head><title>Add Numbers</title></head> <body> <form method="post"> <input name="txtN1" type="text" /><br /> <input name="txtN2" type="text" /><br /> <input name="btnAdd" type="submit" value="Add" /> <p><%=Res%></p> </form> </body> </html> Both use same concepts (variables, conditionals …)

  18. Question: Errors 1 <%@page contentType="text/html" pageEncoding="UTF-8"%> <% double N1; double N2; String Res = ""; if (request.getParameter("btnAdd") != null){ N1 = Double.parseDouble(request.getParameter("txtN1")); N2 = Double.parseDouble(request.getParameter("txtN2")); Res = Double.toString(N1 + N2); } %> <!DOCTYPE html> <html> <head><title>Add Numbers</title></head> <body> <form method="post"> <input name="Num1" type="text" /><br /> <input name="Num2" type="text" /><br /> <input name="btnAdd" type="submit" value="Add" /> <p><%=Res%></p> </form> </body> </html>

  19. Question: Errors 2 <%@page contentType="text/html" pageEncoding="UTF-8"%> <% double N1; double N2; String Res = ""; if (request.getParameter("btnAdd") != null){ N1 = Double.parseDouble(request.getParameter("txtN1")); N2 = Double.parseDouble(request.getParameter("txtN2")); Res = Double.toString(N1 + N2); } %> <!DOCTYPE html> <html> <head><title>Add Numbers</title></head> <body> <form method="post"> <input name="txtN1" type="text" /><br /> <input name="txtN2" type="text" /><br /> <input name="btnAdd" type="button" value="Add" /> <p><%=Res%></p> </form> </body> </html>

  20. Example: Apples Apples.jsp <%@page contentType="text/html" pageEncoding="UTF-8"%> <% double n = 0; int i = 0; String s = ""; if (request.getParameter("btnGo") != null){ n = Double.parseDouble(request.getParameter("txtN")); for(i=0;i<n;i++){ s += "<img src='Apple.gif' />"; } } %> <!DOCTYPE html> <html> <head><title>Add Numbers</title></head> <body> <form method="post"> How many apples do you want? <input name="txtN" type="text" /><br /> <input name="btnGo" type="submit" value="Go" /> <p><%=s%></p> </form> </body> </html> Java code can dynamically add html

  21. Adding JavaScript to JSP pages <%@page contentType="text/html" pageEncoding="UTF-8"%> <% double N1; double N2; String Res = ""; if (request.getParameter("btnAdd") != null){ N1 = Double.parseDouble(request.getParameter("txtN1")); N2 = Double.parseDouble(request.getParameter("txtN2")); Res = Double.toString(N1 + N2); } %> <!DOCTYPE html> <html> <head> <title>Add Numbers</title> <script> function window_onLoad(){ document.getElementById('txtN1').focus(); } </script> </head> <body onload="window_onLoad()"> <form method="post"> <input id="txtN1"name="txtN1" type="text" /><br /> <input name="txtN2" type="text" /><br /> <input name="btnAdd" type="submit" value="Add" /> <p><%=Res%></p> </form> </body> </html> • Add JavaScript as usual • Object needs both • Id (for JavaScript) • Name (for java) • Improves usability

  22. Interactive Debugger • Insert Breakpoint (click line number) • Start Debugger (right click file, click Debug File item)

  23. Servlet • Servlet = • Java program, • running on a web-server • (implemented as a class) • Each JSP page is a Servlet • more on this next week

  24. Tutorial Exercise: Login (client-side) • LEARNING OBJECTIVE:see how vulnerable client-side code is • Task 1: Get the Login (v1) example from the lecture working. • Task 2: Use view source – you should be able to see the code.

  25. Tutorial Exercise: Date • LEARNING OBJECTIVE:create a jsp page, including HTML and server-sidecode • Task 1: Get the Date example from the lecture working. • Task 2: Add code that displays good morning/afternoon/evening/night, depending on the time of day.

  26. Tutorial Exercise: Student Loan • LEARNING OBJECTIVE:create a jsp page, including HTML and server-sidecode from scratch to solve a problem • Task 1: Create a web page that allows the user to enter their salary and the computer calculates the annual and monthly payments for their student loan.Hint: Use the AddNum example from the lecture.

  27. Tutorial Exercise: Login (client-side) • LEARNING OBJECTIVE:create a jsp page, including HTML and server-sidecode from scratch to solve a problem • Task 1: Create a login page that uses server-side code to check the username and password entered by the user.Hint: Use the AddNum example as inspiration. Hint2: Use the following code to send the user to the homepage: response.sendRedirect(“home.htm”); • Task 2: Use view source – you should NOT be able to see the code.

  28. How To: Add a JSP page 1. Right Click Project 2. Click New menu item 3. Click JSP menu item 1. Type a name for your page 2. Click Finish button

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