1. Java Servlets Java Server Pages (JSP)

2. Need for Servlets Servlets are required to:
Reduce the overhead on the server and network
To take care of processing data on the Web server
Servlets are:
Java programs that can be deployed on a Java enabled Web server
Used to extend the functionality of a Web server
Used to add dynamic content to Web pages

3. Characteristics of Servlets
Servlets are:
Efficient
Initialization code for a servlet is executed only once
Robust
Provide all powerful features of Java
Portable across Web servers
Persistent
Increase the performance of a system by preventing frequent disk access

4. Comparison between Servlets and Applets
Are embedded in Web pages
Require the browser to be Java-enabled
Take a lot of time to be downloaded
Servlets:
Execute on the Web server, thus help overcome problems with download time
Do not require the browser to be Java-enabled

5. Comparison between Servlets and other Server-
Side Scripting Technologies
Common Gateway Interface (CGI) scripts, JSP, and ASP are alternatives to servlets
CGI Scripts:
Are programs written in C, C++, or Perl
Get executed in a server
Run in separate processes for each client access
Require the interpreter to be loaded on the server
A JSP file is automatically converted to a servlet before it is executed

6. Comparison between Servlets and other Server- Side Scripting Technologies (Contd.)
Active Server Pages (ASP):
Is a server-side scripting language developed by Microsoft
Enables a developer to combine HTML and a scripting language in the same Web page
Are not compatible with all Web servers

7. Overview of History CGI CGI Servlet JSP Template (ASP, PHP) (in C)
(java, C++)
Template
(ASP, PHP)
complexity
Speed, Security
Servlet
JSP

8. Working of Servlets
Client browser passes requests to a servlet using the
following methods:
GET
Uses a query string to send additional information to the server
Query string is displayed in the client browser
POST
Sends the data as packets to the server through a separate socket connection
Complete transaction is invisible to the client
Slower compared to the GET method

9. The javax.servlet Package
Hierarchy of classes that are used to create a servlet
Class java.lang.Object
Class
javax.servlet.GenericServlet
javax.servlet.HttpServlet
Interface
javax.servlet.Servlet
javax.servlet.ServletConfig
javax.io.Serializable

10. The javax.servlet Package (Contd.)
A brief description of the classes and interfaces are as follows:
Class/Interface Name
Description
HTTPServlet class
Provides a HTTP specific implementation of the Servlet interface.
HTTPServletRequest interface
Provides methods to process requests from the clients.

11. Class/Interface Name
Description
HTTPServlet Response interface
Response to the client is sent in the form of a HTML page through an object of the HTTPServletResponse class.
ServletConfig class
Used to store the servlets startup configuration values and the initialization parameters.

12. Life Cycle of a Servlet Life cycle of a servlet is depicted below:
Client (Browser)
init()
service()
destroy()
Request
Response

13. Life Cycle of a Servlet (Contd.)
The following table describes few methods that are used in creating a servlet:
Method name
Functionality
Servlet.init (ServletConfig config) throws ServletException
Contains all initialization code for the servlet.
Servlet. service()
Receives all requests from clients, identifies the type of the request, and dispatches them to the doGet() or doPost() methods for processing.

14. Life Cycle of a Servlet (Contd.)
Method name
Functionality
Servlet. destroy()
Executes only once when the servlet is removed from server.
HTTPServlet Response. getWriter()
Returns a reference to a PrintWriter object.
HTTPServlet Response. setContentType (String type)
Sets the type of content that is to be sent as response to the client browser.

15. Deploying a Servlet A servlet can be deployed in:
Java Web Server (JWS)
JRun
Apache
Java 2 Enterprise Edition (J2EE) server

16. HelloWorld import java.io.*; import javax.servlet.*;
import javax.servlet.http.*;
public class HelloWorld extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<body>");
out.println("<head>");
out.println("<title>Hello CS764!</title>");
out.println("</head>");
out.println("<h1>Hello CS764!</h1>");
out.println("</body>");
out.println("</html>");
out.close(); }

17. <title>Hello CS764!</title></head> <body>
<html><head></head> <body> <a href="../servlet/HelloWorld"> <h1>Execute HelloWorld Servlet</h1> </a> </body> </html>
<html>
<head>
<title>Hello CS764!</title></head>
<body>
<h1>Hello CS764!</h1>
</body>
</html>

18. Client - Server - DB Web server (Apache, JWS) Client (browser)
Trigger Servlet, JSP (Request)
Web server (Apache, JWS)
Client (browser)
Through internet
Return html file (Response)
Request data
JDBC, intranet
Return data
Database server (DB2)

19. Life Cycle of Servlet servlet HttpServlet GenericServlet
init(ServletConfig);
doGet(HttpServletRequest,
HttpServletResponse);
service(ServletRequest,
ServletResponse);
doPost(HttpServletRequest,
HttpServletResponse);
…….
destroy();

20. Interaction with Client
HttpServletRequest
String getParameter(String)
Enumeration getParameters(String[])
HttpServletResponse
Writer getWriter()
ServletOutputStream getOutputStream()
Handling GET and POST Requests

21. Assignment : Get Stock Price
Ass2.html
<html><head></head>
<body>
<form action="../servlet/Ass2Servlet" method=POST>
<h2>Stock Symbol name:
<input type=text name="stockSymbol"></h2><br>
<input type="submit" value = "get price">
</form>
</body></html>
Client Side

22. Ass2Servlet public class Ass2Servlet extends HttpServlet {
import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Ass2Servlet extends HttpServlet {
public void doPost(HttpServletRequest request,
HttpServletResponse res)
throws IOException, ServletException {
res.setContentType("text/html");
PrintWriter out = res.getWriter();
String stockSymb = request.getParameter("stockSymbol");
StockGrabber sg = new StockGrabber();
sg.setStockSymbol(stockSymb); // Set the stock symbol as “input”
String stockPrice = sg.getPrice();// Get the price of stock
System.out.println("After StockGrabber.getPrice --"+stockPrice);// Debug
out.println("<html><head></head><body><br><br>");
out.println(stockSymb + " -- " + stockPrice);
out.println("<hr>");
out.println("<form action=\"../servlet/Ass2Servlet\" method=POST>");
out.println("<h3>Stock Symbol name: <input type=text name=\"stockSymbol\"></h3>");
out.println("<input type=submit value=\"get price\">");
out.println("</form>");
out.println("</body></html>"); }

23. Session Tracking Session:
Is a group of activities that are performed by a user while accessing a particular Web site
Session Tracking:
Is the process of keeping track of settings across sessions

24. Techniques to Keep Track of Sessions in Servlets
Http:
Cannot be used to maintain data across two sessions
Is a stateless protocol
The following techniques can be used to track sessions data in servlets:
URL rewriting
Hidden form fields
Cookies
Using the HTTPSession interface

25. URL Rewriting
Is a technique by which the URL is modified to include the session ID of a particular user and is sent back to the client
The session ID is used by the client for subsequent transactions with the server

26. Is a technique that can be used to keep track of users
Hidden Form Fields
Is a technique that can be used to keep track of users
The values that are trapped in the hidden fields are sent to the server when the user submits the form

27. Using the HttpSession Interface HttpSession Interface:
Is a part of the Servlet API that is used to keep track of sessions
A user who logs on to a Web site is automatically associated with a session object
The session object can be used to store any type of data for keeping track of sessions

28. Cookies
Are small text files that are used by a Web server to keep track of users
Has values in the form of key-value pairs
Are created by the server and sent to the client with the HTTP response headers
Are saved in the client’s local hard disks and sent along with the HTTP requests headers to the server
Are supported by the Servlet API through javax.servlet.http.Cookie class

29. Need for JSP Caters to the need for server-side scripting
Facilitates segregation of work profiles of a Web designer and a Web developer
The Web designer designs the layout for the Web page by using HTML
The Web developer writes the code for business logic by using Java and other JSP-specific tags
Generates a servlet on compilation, hence incorporates all servlet functionalities

30. Differences between servlets and JSP
Consist of an HTML file for static content and a Java file for dynamic content
Require recompilation if changes are made to any of the files
Involve extensive code writing
JSP:
Contains Java code embedded directly into an HTML page by using special tags
Automatically incorporates changes made to any files
Facilitates independent working of Web developers and Web designers

31. Java Server Pages (JSP)
Client’s Computer
Server
1.Browser requests HTML
7. Server sends HTML
back to browser
servlet
class
5.The servlet runs and generates HTML
Java Engine
6. Java Engine sends HTML to server
2. Server sends requests to Java Engine
3. If needed, the Java Engine
reads the .jsp file
4. The JSP is turned into a
servlet, compiled, and loaded
Bean

32. The JSP request-response cycle

33. A First JSP Calculator.html <html> <head></head>
<body>
<p>Enter two numbers and click the
‘calculate’ button.</p>
<form action=“calculator.jsp” method=“get”>
<input type=text name=value1><br>
<input type=text name=value2 ><br>
<input type=submit name=calculate value=calculate>
</form>
</body>
</html>
Calculator.html

34. Calculator.jsp <html>
<head><title>A simple calculator: results</title></head>
<body>
<%-- A simpler example 1+1=2 --%>
1+1 = <%= 1+1 %>
<%-- A simple calculator --%>
<h2>The sum of your two numbers is:</h2>
<%= Integer.parseInt(request.getParameter("value1")) +
Integer.parseInt(request.getParameter("value2")) %>
</body>
</html>
Calculator.jsp

35. JSP Tags Comments <%-- …...text…... --%>
Declaration <%! int i; %>
<%! int numOfStudents(arg1,..) {} %>
Expression <%= 1+1 %>
Scriptlets <% … java code … %>
include file include file=“*.jsp” %>
…...

36. Using Java Bean Declaration Setting property Getting property
1. <jsp:useBean id=“bean1” class=“Bean1”/>
2. <jsp:useBean id=“bean1” class=“Bean1” name=“serBean” type=“SerBean1”/>
Setting property
1. <jsp:setProperty name=“bean1” property=“color” value=“red”/>
2. <jsp:setProperty name=“bean1” property=“color”/>
3. <jsp:setProperty name=“bean1” property=“color” param=“bgColor”/>
4. <jsp:setProperty name=“bean1” property=“*”/>
Getting property
1. <jsp:getProperty name=“bean1” property=“color”/>
2. <%=bean1.getColor() %>

37. Assg2 example Client side Ass2.html <html>
<head></head>
<body>
<center>
<table border = 0>
<form action=ass2.jsp method = POST>
<tr><td><font color=blue>choose a stock market:</font></td>
<td><select name="stockMarket">
<option value="Waterhouse">Waterhouse</option>
<option value="Yahoo">Yahoo</option>
<option value="ChicagoStockex">Chicago Stockex</option>
<option value="Reuters">Reuters</option>
</select></td>
</tr>
<tr><td><font color = blue>input a stock symbol:</font></td>
<td><input type="edit" name="stockSymbol" size=15></td>
<tr><td></td><td><input type="submit" value = "get price"></td></tr>
</table>
</form></center>
</body></html>
Client side
Ass2.html

38. <jsp:setProperty name=“ass2” property=“stockSymbol”/>
ass2.jsp
<html><head>
<jsp:useBean id="ass2" scope="session" class="ass2.StockGrabber" />
<jsp:setProperty name="ass2" property="*" />
</head>
<body><h2><%
ass2.processInput();
ass2.getPrice();
%>
<center><table border=5>
<tr><td># of data</td> <td>Stock Market</td> <td>Stock Symbol</td> <td>Stock Price </td>
</tr><%
String[] stockMarkets = ass2.getStockMarkets();
String[] symbols = ass2.getSymbols();
String[] prices = ass2.getPrices();
for(int i=0; i<prices.length; i++){
<tr><td> <%= i+1 %> </td>
<td> <%= stockMarkets[i] %> </td>
<td> <%= symbols[i] %> </td>
<td><font color=red><%= prices[i] %></font></td> }
</table>
</center>
</h2>
file="ass2.html" %></html>
<jsp:setProperty name=“ass2” property=“stockSymbol”/>
<jsp:setProperty name=“ass2” property=“stockMarket”/>
Server side

40. Without using JDBC Public class StockGrabber { ...
public void processInput(){
if(stockMarket.compareTo("Waterhouse")==0){
setPrePriceString("<!--Last-->");
setPostPriceString("</FONT>");
setUrlPrefix("
waterhouse/quote.asp?ticker="); }
else if(stockMarket.compareTo("Yahoo")==0){
setPrePriceString("<td nowrap><b>");
setPostPriceString("</b></td>");
setUrlPrefix("
else if(...){}
else{...}

41. Using JDBC --> Database
import java.sql.*;
Public class StockGrabber {
...
public void processInput(){
try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
String sourceURL="jdbc:odbc:stockInfo";
Connection databaseConnection=DriverManager.getConnection(sourceURL);
Statement statement=databaseConnection.createStatement();
ResultSet info =statement.executeQuery(
"select tPrePriceStr, tPostPriceStr, tUrlPrefix
from stockMarketData
where tStockMarket = stockMarket”);
while(inf.next()) {
prePriceString = info.getString(”tPrePriceStr");
postPriceString = info.getString(“tPostPriceStr”);
urlPrefix = info.getString(“tUrlPrefix”); }
catch(SQLException e){ ... }

42. A JSP page consists of HTML and JSP tags
A JSP page consists of HTML and JSP tags. The JSP tags include comments, directives, declarations, scriplets, expressions, and actions
JSP directives are used to specify general information about a particular page
JSP declarations are used to define variables and methods in a page
JSP scriplets consist of valid code snippets placed within the <% and the %> tags

43. JSP expressions are used to directly insert values into the output
JSP actions such as useBean, getProperty, setProperty, and forward are used to perform tasks such as insertion of files, reusing beans, forwarding a user to another page, and instantiating objects
JSP implicit objects such as request, response, out, and session are pre-defined variables that can be added to expressions and scriplets You use the java utility to execute a Java program