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Web programming for project students Dr Jim Briggs.

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Presentation on theme: "Web programming for project students Dr Jim Briggs."— Presentation transcript:

1 Web programming for project students Dr Jim Briggs

2 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

3 Basic architecture of the web

4 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

5 HTTP protocol Specified by – Based on requests and responses A response can contain any document –MIME ( Multipurpose Internet Mail Extensions ) types – A stateless protocol Normally transported via a TCP/IP connection –Default port is TCP 80

6 HTTP requests Requests –GET –POST –PUT –HEAD Example request GET HTTP/1.1

7 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 University of Portsmouth - Our University...

8 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 University of Portsmouth - Our University...

9 Dynamic web pages Four models: –Server-side includes –CGI –Server modules –Auxiliary servers

10 CGI architecture

11 CGI specification Specified at

12 Server module

13 Auxiliary server

14 Common web languages Java/JSP ASP (.NET) / C# PHP Perl Ruby on Rails

15 Architecture of a Java web application

16 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

17 Important classes and interfaces 1 All servlets must implement the Servlet interface Class HttpServlet –init/destroy –doGet/doPut –Your servlet will derive from this

18 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

19 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

20 JSP elements Scriptlets Actions Directives Standard tags Custom tags Expression language

21 Scriptlets Any Java code between Expressions – Declarations – DEPRECATED –Do not use - not XML –Much easier to use JSTL

22 JSP actions Including other files – –Request time inclusion Accessing beans –

23 JSP directives Page directive – Include directive – –Translation time inclusion

24 Java Standard Tag Library (JSTL) Taglib directive – Core – SQL XML Format

25 Custom tags 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

26 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']} ${}

27 Java tools NetBeans –IDE –edit, compile, build, run, debug –lots of wizards –support for Struts –support for Hibernate (through nbxdoclet) Eclipse

28 Web application system architecture

29 Model View Controller (MVC)

30 MVC in Java

31 Relationship between Struts and Hibernate

32 Struts information flow

33 Role of the persistence layer

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