Java Request Dispatcher
- 1. Java/J2EE Programming Training Request Dispatcher
- 2. Page 2Classification: Restricted Agenda • Understand Request Dispatcher • JSP
- 4. Page 4Classification: Restricted num1 num2 Num1= 10 Num2= 20 sum = 30 response Public void doGet(HttpServletRequest req, HttpServletResponse res) { String num= req.getParameter(“num1”); String num2 = req.getParameter(“num2”); int n1 = Integer.parseInt(“num1”); int n2= Integer.parseInt(“num2”); Integer sum= n1 +n2; req.setAttribute(“sum”,sum); }
- 5. Page 6Classification: Restricted FactorialServlet num1 num2 Rd.forward(req, resp) Num1= 10 Num2= 20 Sum = 30 respons e Public void doGet(HttpServletRequest req, HttpServletResponse res) { request.setAttribute(“sum”, sum); RequestDispatcher rd; rd = req.getRequestDispatcher(“fact”); rd.forward(req, res) }
- 6. Page 8Classification: Restricted FactorialServlet num1 num2 Rd.forward (req, resp) Public void doGet(HttpServletRequest req, HttpServletResponse res) { request.setAttribute(“sum”, sum); RequestDispatcher rd; Rd = req.getRequestDispatcher(“fa ct”); rd.forward(req, res) } Num1= 10 Num2= 20 Sum = 30 Response “sum = “ + sum Public void doGet(HttpServletRequest req, HttpServletResponse res) { String sum = req.getAttribute(“sum”).toString(); out.println( “sum = “ + sum ) }
- 7. Page 9Classification: Restricted FactorialServlet num1 num2 Rd.forward (req, resp) Public void doGet(HttpServletRequest req, HttpServletResponse res) { request.setAttribute(“sum”, sum); RequestDispatcher rd; Rd = req.getRequestDispatcher(“fact” ); rd.forward(req, res) } Num1= 10 Num2= 20 Sum = 30 Response “sum = “ + sum Public void doGet(HttpServletRequest req, HttpServletResponse res) { String sum = req.getAttribute(“sum”).toString(); out.println( “sum = “ + sum ) }
- 9. Page 11Classification: Restricted public void doGet(HttpServletRequest req, HttpServletResponse res) { if( valid) { RequestDispatcher rd = req.getRequestDispatcher(“Home.jsp”) rd.forward(req, res); } else { req.setAttribute(“error”, “username or password is invalid”); RequestDispatcher rd =req.getRequestDispatcher(“Login.jsp”); rd.forward(req, res); } } login
- 10. Page 12Classification: Restricted public void doGet(HttpServletRequest req, HttpServletResponse res) { if( valid) { RequestDispatcher rd = req.getRequestDispatcher(“Home.jsp”) rd.forward(req, res); } else { req.setAttribute(“error”, “username or password is invalid”); RequestDispatcher rd =req.getRequestDispatcher(“Login.jsp”); rd.forward(req, res); } } Home About username/pwd invalid login
- 11. Page 13Classification: Restricted public void doGet(HttpServletRequest req, HttpServletResponse res) { if( valid) { RequestDispatcher rd = req.getRequestDispatcher(“Home.jsp”) rd.forward(req, res); } else { req.setAttribute(“error”, “username or password is invalid”); RequestDispatcher rd =req.getRequestDispatcher(“Login.jsp”); rd.forward(req, res); } } Home About L Login.jsp username/pwd invalid ${requestScope.e rror} login error=“username/pwd is invalid
- 12. Page 14Classification: Restricted JSP • Java Server Pages • used for developing server side response • to add dynamic functionality to web page • java code is written inside html • gets the container support • Life Cycle methods • jspInit() • _jspService • jspDestroy
- 13. Page 15Classification: Restricted Compilation & Execution • Execution of jsp is done in two phases • translation • Web container translates Hello.jsp to _Hello.java • Converts jsp to servlet • compilation • generates Hello.class file • load the class file • creates the instance of Hello • calls init method • call service method • calls destroy method.
- 14. Page 16Classification: Restricted Hello.jsp->_Hello.java compiles _Hello.java to _Hello.class