Integrating Servlets and JSP: The Model View Controller - Java ...

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Summary44• Request scope– A new bean instance is made on every HTTP request.– The most common scope.• Session scope– A bean instance could be reused if the request is from thesame user in the same browser session. Useful fortracking user-specific data.• See session tracking lecture for details• Remember to make bean Serializable• Application (ServletContext) scope– Once created, the same bean instance is used for allrequests and all users.• Must synchronize. Very rare.Comparing Data-SharingApproaches: Request• Goal– Display a random number to the user• Type of sharing– Each request should result in a new number, so requestbasedsharing is appropriate.45
Request-Based Sharing: Beanpublic class NumberBean {private final double num;public NumberBean(double number) {this.num = number;}}public double getNumber() {return(num);}The property name in JSP will be “number”. The property name is derived from the method name, not fromthe instance variable name. Also note the lack of a corresponding setter.46Request-Based Sharing: Servlet@WebServlet("/random-number")public class RandomNumberServlet extends HttpServlet {@Overridepublic void doGet(HttpServletRequest request,HttpServletResponse response)throws ServletException, IOException {NumberBean bean =RanUtils.randomNum(request.getParameter("range"));request.setAttribute("randomNum", bean);String address = "/WEB-INF/results/random-num.jsp";RequestDispatcher dispatcher =request.getRequestDispatcher(address);dispatcher.forward(request, response);}}47
Page 4 and 5: Possibilities for Handling aSingle
Page 6 and 7: Review: Beans• Java classes that
Page 8 and 9: MVC Flow of ControlHTML or JSPJava
Page 10 and 11: Request Forwarding Example20public
Page 12 and 13: Request-Based Data Sharing• Servl
Page 14 and 15: ServletContext-Based DataSharing (R
Page 16 and 17: Bank Account Balances:Servlet Code3
Page 18 and 19: Bank Account Balances:Input Form…
Page 20 and 21: Bank Account Balances:High Balance4
Page 24 and 25: Request-Based Sharing:Business Logi
Page 26: Comparing Data-SharingApproaches: S
Page 29 and 30: ServletContext-Based Sharing:Beanpa
Page 31 and 32: © 2012 Marty HallForwarding andInc
Page 33 and 34: Using RequestDispatcher.include:Set
Page 35: © 2012 Marty HallQuestions?JSF 2,

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