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Understanding MVC and Web Application Frameworks for Web Programming

This example presents an introduction to Model-View-Controller (MVC) architecture and web application frameworks through practical application. It explores the transition from traditional JSP-based approach to MVC and discusses the advantages, problems, and implications for web development.

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Understanding MVC and Web Application Frameworks for Web Programming

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  1. CS520 Web ProgrammingIntroduction to MVC and Web Application Frameworks Chengyu Sun California State University, Los Angeles

  2. Example – Items (JSP version) • Login.jsp • authentication No session attribute admin No session attribute user set session attribute admin set session attribute user • Admin.jsp • display items • adding new items • User.jsp • display items logout logout • Logout.jsp • invalidate session

  3. About Items (JSP version) • Advantages • Easy to code • Problems • ??

  4. Model 1 Architecture • JSPs + Java beans • JSPs for presentation • beans for business logic JSP 3 JSP 1 JSP 4 JSP 2

  5. Java Beans • POJO (Plain Old Java Objects) • Properties defined by getter and setter methods

  6. Items (Model 1 version) • What would it look like?? • Compared to the JSP version, what problems are addressed and what still remain??

  7. Model 2 Architecture • Also know as Model-View-Controler (MVC) architecture • JSPs + beans + servlet • Beans for business logic – Model • JSPs for presentations – View • servlet for web logic – Controller • HTTP related processing, e.g. request, response, sessions etc. • Request dispatching

  8. MVC Control Flow ... model 2 3 controller 1 4 user view 5

  9. ... MVC Control Flow • Process request • Populate beans • Store results in request, session, or servlet context • Forward request to JSP page • Extract bean data from beans and display

  10. Multiple Controllers Front Controller … … Controller Controller Controller … … view model view model

  11. Items (MVC version) • FrontController • Login handler • Logout handler • User handler • Admin handler • Models: Item and User • Views: Login.jsp, Admin.jsp, User.jsp

  12. Admin Control Flow 1. Process request 2. Populate beans List<Item> items = itemDao.getAllItems(); 3. Store results in request, session, or servlet context request.setAttribute( "items", items ); 4. Forward request to JSP page request.getRequestDispatcher( "WEB-INF/jsp/Admin.jsp" ).forward( request, response ); 5. Extract bean data from beans and display <c:forEach items="${items}" var="item"> …

  13. More About The Example • web.xml • Data Access Object (DAO) Persistent Data Store DAO controller model view user

  14. Recommended by SUN: http://java.sun.com/blueprints/code/projectconventions.html Directory Structure …

  15. … Directory Structure • Recommended by This SUN: \webapp \build \dist \conf \doc \db \lib \compile \runtime \src \web \WEB-INF \jsp \tld build.xml build.properties.sample

  16. Need for Web Application Frameworks • What are missing from Items (MVC version)??

  17. Some Web Application Frameworks • Struts • http://struts.apache.org/ • Spring • http://www.springframework.org/ • More than a MVC framework • Ruby on Rails • http://www.rubyonrails.org/

  18. Web App Development – Where Do We Start? • Control flow driven approach Products Shoping Cart Credit Info checkout buy search Search Results

  19. Web App Development – Where Do We Start? • Data driven approach 3. Application 1. Models 2. Database Schema

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