Introduction To HTML Dr. Magdi AMER

HTML elements

Tables

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Forms

Web Architecture 7

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 HTTP Get Request 8

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. HTTP Post Request 9

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

– As a link:  always GET go – As a form action  can choose GETor POST …. Calling a Servlet 11

//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]; Reading Parameters 12

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 Parameters Types 13

HelloWorld eg.edu.ufe.tic4.HelloWorld HelloWorld /hi HelloWorld *.php web.xml 14

History of the web 15

Class Variable (static) Instance Variable Function Variable Single Threaded SharedUnique Multi- Threaded Shared Unique Handling Multi-threads 16

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; } 17

page contentType="text/html;charset=UTF-8" import="com.amer.*”%> <% //java code out.println(“ NAME”); %>  JSP 18

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

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

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

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”); 22