Web programming for project students

Transcript Web programming for project students

Web programming
for project students
Dr Jim Briggs
What is the web?
• Distributed system
• Client-server system
• Characteristics of clients and servers
– Servers always on / Clients choose when on
– Clients do not need high performance if the
work is done on the server
• Protocol based
Basic architecture of the web
Common web tools
• Browsers
– Microsoft Internet
Explorer
– Netscape Navigator
– Mozilla (Firefox)
– Opera
– Safari
– Konqueror
– Lynx
• Servers
– Apache
– Internet Information
Server (Microsoft)
– Sun
– Netscape
– Omni
– Roxen
– NCSA
HTTP protocol
• Specified by
– http://www.w3.org/Protocols/rfc2616/rfc2616.html
• Based on requests and responses
• A response can contain any document
– MIME (Multipurpose Internet Mail Extensions) types
– http://www.iana.org/assignments/media-types/
• A stateless protocol
• Normally transported via a TCP/IP connection
– Default port is TCP 80
HTTP requests
• Requests
– GET
– POST
– PUT
– HEAD
• Example request
GET http://www.port.ac.uk/index.htm HTTP/1.1
HTTP responses
HTTP/1.1 200 OK
Server: Microsoft-IIS/4.0
Date: Mon, 29 Apr 2002 08:50:53 GMT
Content-Type: text/html
Accept-Ranges: bytes
Last-Modified: Wed, 10 Apr 2002 16:12:34 GMT
ETag: "085fb85aae0c11:54fb"
Content-Length: 13845
<HTML>
<HEAD>
<TITLE>University of Portsmouth - Our
University</TITLE>
...
An error response
HTTP/1.1 404 Object Not Found
Server: Microsoft-IIS/4.0
Date: Mon, 29 Apr 2002 08:58:12 GMT
Content-Length: 11891
Content-Type: text/html
<HTML>
<HEAD>
<TITLE>University of Portsmouth - Our
University</TITLE>
...
Dynamic web pages
• Four models:
– Server-side includes
– CGI
– Server modules
– Auxiliary servers
CGI architecture
CGI specification
• Specified at
http://hoohoo.ncsa.uiuc.edu/cgi/
Server module
Auxiliary server
Common web languages
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Java/JSP
ASP (.NET) / C#
PHP
Perl
Ruby on Rails
Architecture of a
Java web application
Introduction to Java web apps
• Servlets and JSPs
• Servlet container
– Tomcat
• A container may run several (independent)
web applications (webapps)
• Each must have a WEB-INF directory:
– web.xml configuration file
– classes directory
– lib directory
Important classes and
interfaces 1
• All servlets must implement the Servlet
interface
• Class HttpServlet
– init/destroy
– doGet/doPut
– Your servlet will derive from this
Important classes and
interfaces 2
• 2 parameters to a request handling
method
• Class HttpServletRequest
– String param = request.getParameter(name);
• Class HttpServletResponse
– PrintWriter out = response.getWriter();
• Class HttpSession
– Holds data common to related requests
JavaServer Pages (JSP)
• Distinction:
– servlets: HTML embedded in program
– JSP: program embedded in HTML
• Useful where majority of effort is page design
• Translated automatically into a servlet
– Retranslated if changed (no need to restart server)
• Can be placed anywhere in a web application
– but not visible to client if in the WEB-INF directory
JSP elements
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Scriptlets
Actions
Directives
Standard tags
Custom tags
Expression language
Scriptlets
• Any Java code between <% … %>
• Expressions
– <%= name %>
• Declarations
– <%! String name %>
• DEPRECATED
– Do not use - not XML
– Much easier to use JSTL
JSP actions
• Including other files
– <jsp:include page="path"/>
– Request time inclusion
• Accessing beans
– <jsp:usebean id="beanName" class="package.class"
scope="session"/>
– <jsp:getproperty name="beanName"
property="propertyName"/>
– <jsp:setproperty name="beanName"
property="propertyName" value="newValue"/>
JSP directives
• Page directive
– <%@page import="package.class"%>
– <%@page contentType="text/html"%>
– <%@page errorPage="URL"%>
• Include directive
– <%@include file="filename"%>
– Translation time inclusion
Java Standard Tag Library (JSTL)
• Taglib directive
– <%@ taglib prefix="c"
uri="http://java.sun.com/jstl/core" %>
• Core
– <c:out value="${anExpression}"/>
• SQL
• XML
• Format
Custom tags
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Implement your own tags
Create a Tag Library Definition (tld) file
Extend predefined classes
Specify your library in a @taglib directive
Use like JSTL tags
Expression language
• Refer to Java Beans and other common classes
• ${expression} can appear as tag attributes or
(since JSP 2.0) in the page itself
• Several implicit objects:
– header
• ${header["user-agent"]}
– param
• ${param['name']}
• ${param.name}
Java tools
• NetBeans
– IDE
– edit, compile, build, run, debug
– lots of wizards
– support for Struts
– support for Hibernate (through nbxdoclet)
• Eclipse
Web application
system architecture
Model View Controller (MVC)
MVC in Java
Relationship between
Struts and Hibernate
Struts information flow
Role of the persistence layer

Web programming for project students

Transcript Web programming for project students

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