1 Web Programming with Servlets & JSPs WEB APPLICATIONS – AN OVERVIEW

Objectives  Web Client – Server Model  Evolution of Servlets  Web Application  Web Application Development Process  Servlet API  Workshops 2

Client – Server Model 3 Advantages of Web Application Easier access to information Lower maintenance and deployment costs Platform independency Wider visibility

Architecture of Web Applications 4 N – tiers Architecture

5 How Web Server works ? Translate 2. Server name – Microsoft.com 3. File name – index.htm 1. Protocol – HTTP address Connect Browser send a GET request Server response as HTML format

6 Web server …? File system contains HelloWorld.html

Communication/ Protocols Http Protocol Request Message structures Response Message structures

Request Objects 8  Request Parameters  Request Methods

Limitation of Web Servers 9  Not feasible to maintain static content from the customer’s end  Can not be managed the dynamic Web contain from client  Overloading errors  Unavailability due to maintenance  Heavy traffic  High maintenance costs  Virus or worms attacks

10 Architechture : Web Application Collect information Send Request to Web ServerExecute Server Script Response result to browser

11 Server Side Script  Common Gateway Interface (CGI).  ISAPI  Server-side JavaScript (SSJS).  Personal Home Page (PHP).  Java Servlet  Active Server Page (ASP)  Java Server Page (JSP).  Ruby on Rail  ASP.net  …………………………………..

CGI 12 Disadvantages Reduced efficiency Reloading Perl interpreter No Session #include void main() { printf(“ \n”); printf(“ My CGI program \n”); printf(“ Hello \n”); printf(“ \n”); }

Servlets 13

Web Application 14  Concepts  Registered into WWW  Accessible from a public server  Comprises servlets, JSPs, images, HTML, JavaBeans, applets, and Java classes  Portability  Store in WAR files to deploy on the Web server

Web Application Directory Structure 15

Web Deployment Descriptor – web.xml servlet name [package.]classname servlet name /context Path/root 30 default page to show Place in WEB-INF folder

Example HelloServlet demo.HelloServlet HelloServlet /Welcome Welcome index.jsp Alias Name

Web Application Development Process in NetBeans 18  Step 1: Creating a new project  Step 2: Specifying Name and Location for the Project  Step 3: Creating the new Web files.  Step 4: Specifying the Name of the Servlets  Step 5: Writing the code for Servlet & Compile  Step 6: Package Servlet into WAR file  Step 7: Deploying in a Web Container  Step 8: Executing the Servlet

Creating a new project  Click menu File  Click the “New Project” Items

Creating the new Web Project  Click Web categories  Click the “Web Application” Projects  Click Next button

Specifying Name and Location for the Project Fill your project name Browser your location where store the project  Click Finish button

Choose Server 22 Choose WebServer and Context Path, click “Next”, “Finish”

Web Application Directory Structure in Netbeans Project name Interactive Web Directory Web Deployment descriptor Configuration directory related define for Web App Source java class required for Web App Lib directory required for Web App

Create Servlet 24

Named for Servlet 25 Name Must have Package name Click :”Next”  “Finish”

Writing the code for Servlet & Compile  Modify the processRequest method in servlet class. Ex: protected void processRequest (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType ("text/html;charset=UTF-8"); PrintWriter out = response.getWriter (); out.println(" "); out.println(" Hello Servlet "); out.println(" "); out.println(" Welcome to Servlet course "); out.println(" "); out.close (); }

Writing the code for Servlet & Compile (cont)

Package Servlet into WAR file  Package War file with command prompt  jar –cvf fileName.war directoryOrFile (using blank to separate)  Ex: jar –cvf HelloServlet.war *.jsp WEB-INF/*  You can manual deploy this application : copy.war file to folder TOMCAT_HOME/webapps

Executing the Servlet

GenericServlet Class 30

HTTPServlet Class 31

Workshop Activities 32 Building the first Servlet named HelloServlets to greet the user “Hello Servlets” in the Web browser. Notes: The NetBean runs the Servlet with the Tomcat Server version