Web Systems

Nov. 21, 2017

Web State Management Techniques

· Cookies

· Sessions

o Local Web Storage

o Session Storage

HTML Web Storage, W3C Recommendation, 2016/4/19, http://www.w3.org/TR/webstorage/

· The API

o The Storage Interface

§ The sessionStorage attribute

§ The localStorage attribute

§ The storage event

o Threads

· Disk Space

· Privacy

o User tracking

o Sensitivity of data

· Security

o DNS spoofing attacks

o Cross-directory attacks

o Implementation risks

Web Storage Concepts and Usage, https://developer.mozilla.org/en-US/docs/Web/API/Web_Storage_API

· window.sessionStorage

· window.localStoarge

Windo.sessionStorage, https://developer.mozilla.org/en-US/docs/Web/API/Window/sessionStorage

// Save data to sessionStorage

sessionStorage.setItem('key', 'value');

// Get saved data from sessionStorage

var data = sessionStorage.getItem('key');

// Remove saved data from sessionStorage

sessionStorage.removeItem('key');

// Remove all saved data from sessionStorage

sessionStorage.clear();

LocalStorage, https://developer.mozilla.org/en-US/docs/Web/API/Storage/LocalStorage

// Save data to the current local store

localStorage.setItem("username", "John");

// Access some stored data

alert( "username = " + localStorage.getItem("username"));

HTML Web Storage, State Management

· HTML5 5.4 Session History and Navigation, http://www.w3.org/TR/2011/WD-html5-20110113/history.html

· Identifying Application State, Dec. 1, 2011, http://www.w3.org/2001/tag/doc/IdentifyingApplicationState

· History objects

interface History {

readonly attribute long length;

void go(in optional long delta);

void back();

void forward();

void pushState(in any data, in DOMString title, in optional DOMString url);

void replaceState(in any data, in DOMString title, in optional DOMString url);

};

interface Location {

stringifier attribute DOMString href;

void assign(in DOMString url);

void replace(in DOMString url);

void reload();

// URL decomposition IDL attributes

attribute DOMString protocol;

attribute DOMString host;

attribute DOMString hostname;

attribute DOMString port;

attribute DOMString pathname;

attribute DOMString search;

attribute DOMString hash;

// resolving relative URLs

DOMString resolveURL(in DOMString url);

};

PHP Cookies and Sessions

· $_COOKIES, http://php.net/manual/en/reserved.variables.cookies.php

· $_SESSION

o Basic Usage, http://php.net/manual/en/session.examples.basic.php

· bool session_start([array $option =[])), http://php.net/manual/en/function.session-start.php

· References http://php.net/manual/en/reserved.variables.session.php

Example # 1 Registering a variable with $_SESSION

<?php
session_start();
if (!isset($_SESSION['count'])) {
$_SESSION['count'] = 0;
} else {
$_SESSION['count']++;
}
?>

Example #2 Unregistering a variable with $_SESSION

<?php
session_start();
unset($_SESSION['count']);
?>

<?php

Example page1.php

http://php.net/manual/en/function.session-start.php

// page1.php

session_start();

echo 'Welcome to page #1';

$_SESSION['favcolor'] = 'green';
$_SESSION['animal']   = 'cat';
$_SESSION['time']     = time();

// Works if session cookie was accepted
echo '<br /><a href="page2.php">page 2</a>';

// Or maybe pass along the session id, if needed
echo '<br /><a href="page2.php?' . SID . '">page 2</a>';
?>

How to use Storage and Session Variables across pages? https://stackoverflow.com/questions/5489365/how-to-use-store-and-use-session-variables-across-pages