Understanding Cookies: Storage, Location, and Usage with Active Server Pages, Slides of Fundamentals of E-Commerce

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Server-Side Web Programming

with Active Server Pages

Cookies Overview

Introduction

-^ Cookies are small pieces of information stored bythe webserver on the client’s machine. •^ Cookie information is saved in small files createdand saved by the client’s browser. •^ Cookie information is sent back to the webserverthat generated the cookie. •^ Originally developed by Netscape. Now definedby RFC 2109 (“

HTTP State Management Mechanism

-^ Developed as a mechanism to maintain statebetween client requests.

Cookie Viewing Demonstration

Setting Cookies via HTTP (1) A cookie is sent to client

by the webserver

using a one-

line HTTP response header. Set-Cookie: NAME=VALUE;

expires=DATE; domain=DOMAIN_NAME;

path=PATH; secure e.g., Set-Cookie: UserID=234;

domain=valtara.com; path=/;

expires=Monday, 10-Nov-1999 23:59:59Set-Cookie: TestVal=test; domain=valtara.com; path=/test/;expires=Monday, 10-Nov-1999 23:59:

Sending Cookies via HTTP When client navigates to a URL with a matchingcookie, browser sends an HTTP request header: Cookie:Name1=Value1;Name2=Value2;… e.g., if client visits Valtara home page, browsersends this cookie to webserver: Cookie: UserID=1 e.g., if client visits Valtara /test/ directory,browser sends both of these cookies, Cookie: UserID=1Cookie: TestVal=test

Cookies

-^ Cookie management systems are browser-specific. •^ Programming languages like ASP abstract cookiewriting/retrieval so you don’t need to know how theclient is managing their cookies.

Cookie Properties

-^ Expires

: Number of days to persist cookie. Typically use

date+x

days or set to a specific

date with

-^ Domain

: Domain cookie originated from. Only used when you only want cookies sent to aspecific subdomain (e.g., sub1.mydomain.com vs.sub2.mydomain.com). • Path

: Virtual path cookie originated from. Only used when only want cookies sent for pages in aspecific path (e.g., /mypath). Path must matchcase of your webserver.

Cookies Properties

-^ HasKeys:

If cookie is a dictionary cookie, returns TRUE. Otherwise, returns FALSE. • Count:

Count of values in a dictionary cookie.

-^ Secure

: When present, instructs browser to send cookie encrypted to the

Path

only using HTTPS.

Rarely used since you normally want to avoidsensitive information in your cookies.

Writing Cookies in ASP

-^ Writing a single cookie: Response.Cookies("MyCookie") = MyValueResponse.Cookies("DicCookie")("Val1") = "Value1" Setting the Cookie Expiration Response.Cookies("MyCookie").Expires = date + 1Response.Cookies("MyCookie").Expires = #1/1/2000# •^ Setting other cookie attributes: Response.Cookies("MyCookie").Domain = "valtara.com"Response.Cookies("MyCookie").Path = "/test" Response.Cookies("MyCookie").Secure = True

Writing Cookies in ASP

•^ Writing values to a dictionary cookie: Response.Cookies("MyCookie")("1stVal") = 1Response.Cookies("MyCookie")("2ndVal") = 2 •^ Generally you want to use dictionary cookies,even if you have only one value, because youwill probably want to add other values laterand will the multiple name/value pairs.