2 Web Application Architecture

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Web Application Architecture

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Agenda

Web components and Web container Web application development and deployment

steps Building Simple Web Applications using Netbeans

and Tomcat Web Application Archive (*.war file)

*.war directory structure WEB-INF subdirectory Configuring Web application deployment descriptor (web.xml

file)

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Web Components & Web Container

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Web Components & Web Container Web components are in the form of either Servlet or JSP

(along with JavaBean’s and custom tags) Web components run in Web container

Tomcat and Resin are popular web containers All Java EE compliant app servers (Sun Java System App

Server) provide web containers Web container provides system services to Web

components Request dispatching, security, and life cycle management

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Web Application & Components Web Application is a deployable package

Web components ( Servlets and JSP) Static resource files such as images Helper classes Libraries Deployment descriptor (web.xml file)

Web Application can be represented as a hierarchy of directories and files (unpacked form)

or *.WAR file reflecting the same hierarchy (packed

form)

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Web application development and deployment steps

1: Write and compile the Web component code (Servlet or JSP) and helper classes referenced by the web component code

2: Create any static resources:for example, images or HTML pages

3: Create deployment descriptor (web.xml)4: Build the Web application (*.war file or deployment-

ready directory)5: Deploy the web application into a Web container6: Web clients are now ready to access them via URL

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1: Write and compile the Webcomponent code Create development tree structureKeep Web application source separate from

compiled files facilitate iterative development

Root directory src: Java source of servlets and JavaBeans

components web: JSP pages and HTML pages, images build.xml: Ant build file

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2: Create any static resources

HTML pageswelcomePage.html

Image files that are used by HTML pages or JSP pagesExample: dukeWaving.png

Both are located at web directory of tree structure

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Example: Hello Tree Structure

Hellosrc

ResultServlet.javaweb

WEB-INF web.xml

welcomePage.html dukeWaving.png

build.xml

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3: Create deployment descriptor (web.xml)

Deployment descriptor contains deployment time runtime instructions to the Web container URL that the client uses to access the web

component Every web application has to have it

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4: Build the Web application Either *.WAR file or unpacked form of *.WAR file

Build process is made ofcreate build directory (if it is not present) and

its subdirectoriescopy image files into build directorycopy web.xml file into build/WEB-INF

directorycompile Java code into build/WEB-

INF/classes directory

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Example: hello Tree Structure after build processing Hellosrcwebbuild.xmlbuild

welcomePage.html dukeWaving.png WEB-INF

web.xml classes

ResultServlet.class

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5: Deploy the web application into a Web container

Deploy the application over deployment platform such asSun Java System App Server orApache Tomcat

6: Web clients are now ready to access them via URL

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Case Study: Web Application

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File | New Project: Java Web | Web Application

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Choose Project Name and Location

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Choose Apache Tomcat to be Server

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New HTML…: welcomePage.html

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Source codes for welcomePage.html<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>

<head><title>Hello</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

</head><body>

<form action="result"><img src="dukeWaving.png" width="79" height="62" /><br><h1> Hello, my name is Duke. What's yours?</h1> <br><br><input type="text" name="username" /><br><br><input type="submit" value="Submit" /><input type=“reset" value="Reset" />

</form></body>

</html>

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Copy image into Hello\web

ใชวิธี drag and drop

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Deploy & Run Project

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Accessing Web Application by browser

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Source codes for welcomePage.html<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>

<head><title>Hello</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

</head><body>

<form action="result"><img src="dukeWaving.png" width="79" height="62" /><br><h1> Hello, my name is Duke. What's yours?</h1> <br><br><input type="text" name="username" /><br><br><input type="submit" value="Submit" /><input type=“reset" value="Reset" />

</form></body>

</html>

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New|Servlet…: ResultServlet: servlets

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Set URL Pattern : /result

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ResultServlet.java...protected void processRequest(HttpServletRequest request,

HttpServletResponse response)throws ServletException, IOException {

response.setContentType("text/html;charset=UTF-8");PrintWriter out = response.getWriter();try {

///* TODO output your page hereout.println("<html>");out.println("<head>");out.println("<title>Servlet ResultServlet</title>"); out.println("</head>");out.println("<body>");

String username = request.getParameter("username");out.println("<h1>Hello " + username + "</h1>");

out.println("</body>");out.println("</html>");

} finally { out.close();

}}

...

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web.xml<?xml version="1.0" encoding="UTF-8"?><web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaeehttp://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"><servlet>

<servlet-name>ResultServlet</servlet-name><servlet-class>servlets.ResultServlet</servlet-class>

</servlet><servlet-mapping>

<servlet-name>ResultServlet</servlet-name><url-pattern>/result</url-pattern>

</servlet-mapping><session-config>

<session-timeout>30

</session-timeout></session-config><welcome-file-list>

<welcome-file>index.jsp</welcome-file></welcome-file-list>

</web-app>

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Clean & Build and Deploy ใหมRun ไฟล : welcomePage.html

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Web Application

Web application can be deployed in two different formsa *.war file oran unpacked directory laid out in the same

format as a *.war file (build directory) Use *.war file when you have to deploy on

a remote machine

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What is *.war file ? Ready to deployable package over web

container Similar to *.jar file Contains things to be deployed

Web components (servlets or JSPs) Server-side utility classes Static Web presentation content (HTML, image, etc) Client-side classes (applets and utility classes)

Reflects contents in build directory

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Directory Structure of *.WAR file

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Directory Structure of *.WAR fileRoot

WEB-INF

JSP pages,static HTML pagesapplet classes, etc.

web.xmlsun-web.xml*.tld

Libraryarchive files

all server-side.class files to this web modules

all .tag files forthis web module

tagslib classes

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WEB-INF Directory Subdirectory of Document root Contains

web.xml : Web application deployment descriptor JSP tag library descriptor files classes : A directory that contains server-side

classes: servlets, utility classes, and JavaBeans components

lib : A directory that contains JAR archives of libraries (tag libraries and any utility libraries called by server-side classes)

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Request URL: User specified access point of a web resource http://[host]:[port]/[request path] ?[query string]

[request path] is made of context and web component’s URN

http://localhost:8080/Hello/result?username=John

Context: Name of the root document of a web application – Identifies a particular applicationon that server /Hello is context

HTTP request URL & Web componentURN (alias) & Context

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Alias Paths (of web.xml) When a request is received by Servlet container, it must

determine which web component in a which web application should handle the request. It does so by mapping the URL path contained in the request to

a web component A URL path contains the context root and alias path

http://<host>:8080/context_root/alias_path Alias Path can be in the form of either

/alias-string (for servlet) or /*.jsp (for JSP)

Configuration information is specified in web.xml (Web Applications Deployment Descriptor)

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web.xml<?xml version="1.0" encoding="UTF-8"?><web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaeehttp://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"><servlet>

<servlet-name>ResultServlet</servlet-name><servlet-class>servlets.ResultServlet</servlet-class>

</servlet><servlet-mapping>

<servlet-name>ResultServlet</servlet-name><url-pattern>/result</url-pattern>

</servlet-mapping><session-config>

<session-timeout>30

</session-timeout></session-config><welcome-file-list>

<welcome-file>index.jsp</welcome-file></welcome-file-list>

</web-app>

welcomePage.html

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Acknowledgement

contents are borrowed from thepresentation slides of Sang Shin, Java™Technology Evangelist, Sun Microsystems,Inc.www.javapassion.com

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2 Web Application Architecture