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Introduction To HTML

Introduction To HTML. Dr. Magdi AMER. HTML elements. Tables. Links. <a href =‘www.ite.com’> click here </a>. Forms. Forms. Web Architecture. HTTP Get Request. An HTTP request has three parts, separated by spaces: A method name The local path of the requested resource (URI)

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Introduction To HTML

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  1. Introduction To HTML Dr. Magdi AMER

  2. HTML elements

  3. Tables

  4. Links <a href=‘www.ite.com’> click here </a>

  5. Forms

  6. Forms

  7. Web Architecture

  8. HTTP Get Request • An HTTP request has three parts, separated by spaces: • A method name • The local path of the requested resource (URI) • The version of HTTP being used GET /reports/sales/index.html HTTP/1.1 • If parameters are required, they are passed by appending a query string to the URI name1=value1&name2=value2&…&nameM=valueM

  9. HTTP Post Request • In POST, the parameters are sent in the message body, unlike in GET, in which they are a part of the request URI. • Post result cannot be bookmarked, while get result can be bookmarked.

  10. First Servlet package com.amer; import java.io.*; import javax.servlet.*; import javax.servlet.http.*;  public class HelloWorld extends HttpServlet {  public void doPost(HttpServletRequestreq, HttpServletResponse res) throws ServletException, IOException { doGet(req, res);} public void doGet(HttpServletRequestreq, HttpServletResponse res) throws ServletException, IOException { res.setContentType("text/html"); PrintWriter out = res.getWriter();  out.println("<HTML>"); out.println("<HEAD><TITLE>Hello World</TITLE></HEAD>"); out.println("<BODY>"); out.println("<BIG>Hello World</BIG>"); out.println("</BODY></HTML>"); }}

  11. Calling a Servlet • As a link:  always GET <a href=‘/appName/HelloWorld?var1=value&var2=value2’> go</a> • As a form action  can choose GETor POST <form method=‘GET’ action=‘/appName/HelloWorld’> ….</form>

  12. Reading Parameters //Single parameter String uname= request.getParameter("uname"); String gender = request.getParameter(“gender”); If(gender == null) gender=“”; //Multi parameters String[] langs = request.getParameterValues("lang"); if(langs==null) langs = new String[0];

  13. Parameters Types Input type: text, password, hidden, single combo, text area  single, never null • Input type: radio, submit •  single, may be null • Input type: checkbox, multi combo •  multi, may be null

  14. web.xml • <?xml version = '1.0' encoding = 'UTF-8'?> • <servlet> • <servlet-name>HelloWorld</servlet-name> • <servlet-class>eg.edu.ufe.tic4.HelloWorld</servlet-class> • </servlet> • <servlet-mapping> • <servlet-name>HelloWorld</servlet-name> • <url-pattern>/hi</url-pattern> • </servlet-mapping> • <servlet-mapping> • <servlet-name>HelloWorld</servlet-name> • <url-pattern>*.php</url-pattern> • </servlet-mapping> • </web-app>

  15. History of the web

  16. Handling Multi-threads

  17. Handling Multi-treading 1- do not use instence variables or shared objects in servlets 2- If really necessary use synchronized synchronized(this) { int y= x; // x is an instance variable, shared between multiple threads // y is a function variable, unique for each thread y = y+100; x = y; }

  18. JSP <%@ page contentType="text/html;charset=UTF-8" import="com.amer.*”%> <%@ page import=“java.util.*" %> <select name=‘gov’> <% //java code out.println(“<BR/>NAME”); %> </select> <%=variable%>  <%out.print(variable);%> <%! //variable and function declaration %> <BR>

  19. JSP to Servlet import com.amer.*; public class JspToServlet extends HttpServlet { //variable and function declaration public void doPost(HttpServletRequestreq, HttpServletResponse res) throws ServletException, IOException { doGet(req, res);} public void doGet(HttpServletRequestreq, HttpServletResponse res) throws ServletException, IOException {  PrintWriter out = res.getWriter(); res.setContentType("text/html"); res.setCharacterEncoding(“UTF-8”); //java code out,print(“<BR/>NAME”): out.print(variable); out.println(“<BR>”); }

  20. Dispatching request from Servlet to JSP RequestDispatcher dispatcher = this.getServletContext(). getRequestDispatcher("/Login.jsp"); dispatcher.forward(request, response);

  21. Passing data from Servlet to JSP //Servlet 1 Vector<Employee> list = null; //………… request.setAttribute(“list”, list); //JSP <% Vector<Employee> list = (Vector<Employee>) request.getAttribute(“list”); %>

  22. Sessions //to create a session HttpSession session = req.getSession(true); User u = new User(); //any object // to store a value in the session session.setAttribute(“user”, u); //////////////////////////////////// //To obtain an instance of an existing session HttpSession session = req.getSession(); // to read a value User u = (User) session.getAttribute(“user”);

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