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|---|---|---|
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Nav: Workbook :: Generating Responses
Handling Cookies
Cookie
A cookie is a piece of data that can be stored in a browser's cache. If you visit a web site and then revisit it, the cookie data can be used to identify you as a return visitor. Cookies enable state information, such as an online shopping cart, to be remembered. A cookie can be short term, holding data for a single web session, that is, until you close the browser, or a cookie can be longer term, holding data for a week or a year.
Cookies are used a lot in web client-server communication.
-
HTTP State Management With Cookies
-
Personalized response to the client based on their preference, for example we can set background color as cookie in client browser and then use it to customize response background color, image etc.
Server send cookies to the client
Set-Cookie: _Framework=EWF; Path=/; Expires=Tue, 10 Mar 2015 13:28:10 GMT; HttpOnly%R
Client send cookies to server
Cookie: _Framework=EWF
Cookie properties
- Comment: describe the purpose of the cookie. Note that server doesn’t receive this information when client sends cookie in request header.
- Domain: domain name for the cookie.
- Expiration/MaxAge: Expiration time of the cookie, we could also set it in seconds. (At the moment Max-Age attribute is not supported)
- Name: name of the cookie.
- Path: path on the server to which the browser returns this cookie. Path instruct the browser to send cookie to a particular resource.
- Secure: True, if the browser is sending cookies only over a secure protocol, False in other case.
- Value: Value of th cookie as string.
- HttpOnly: Checks whether this Cookie has been marked as HttpOnly.
- Version:
Write and Read Cookies.
To send a cookie to the client we should use the HTTP_HEADER class, and call h.put_cookie feature or
h.put_cookie_with_expiration_date feature, see How to set Cookies to learn the details, and the set it to response object WSF_RESPONSE as we saw previously.
We will show an example.
To Read incomming cookies we can read all the cookies with
cookies: ITERABLE [WSF_VALUE]
-- All cookies.
which return an interable of WSF_VALUE objects corresponding to the cookies the browser has associated with the web site. We can also check if a particular cookie by name using
WSF_REQUEST.cookie (a_name: READABLE_STRING_GENERAL): detachable WSF_VALUE
-- Field for name `a_name'.
feature.
How to set Cookies
Here we have the feature definitions to set cookies
deferred class interface
HTTP_HEADER_MODIFIER
feature -- Cookie
put_cookie (key, value: READABLE_STRING_8; expiration, path, domain: detachable READABLE_STRING_8; secure, http_only: BOOLEAN)
-- Set a cookie on the client's machine
-- with key 'key' and value 'value'.
-- Note: you should avoid using "localhost" as `domain' for local cookies
-- since they are not always handled by browser (for instance Chrome)
require
make_sense: (key /= Void and value /= Void) and then (not key.is_empty and not value.is_empty)
domain_without_port_info: domain /= Void implies domain.index_of (':', 1) = 0
put_cookie_with_expiration_date (key, value: READABLE_STRING_8; expiration: DATE_TIME; path, domain: detachable READABLE_STRING_8; secure, http_only: BOOLEAN)
-- Set a cookie on the client's machine
-- with key 'key' and value 'value'.
require
make_sense: (key /= Void and value /= Void) and then (not key.is_empty and not value.is_empty)
Example of use:
response_with_cookies (res: WSF_RESPONSE)
local
l_message: STRING
l_header: HTTP_HEADER
l_time: HTTP_DATE
do
create l_header.make
create l_time.make_now_utc
l_time.date_time.day_add (40)
l_header.put_content_type_text_html
l_header.put_cookie_with_expiration_date ("EWFCookie", "EXAMPLE",l_time.date_time, "/", Void, False, True)
res.put_header_text (l_header.string)
res.put_string (web_page)
end
How to read Cookies
Reading a particular cookie
if req.cookie ("EWFCookie") = Void then
do_something
end
Reading all the cookies
across req.cookies as ic loop
print (ic.item.name)
end
Example
The following EWF service shows a basic use of cookies. 1. It display a message to first-time visitors. 2. Display a welcome back message if a visitor return. 3. A visitor page, counting the number of visits to the page (track user access counts). 4. A cookie with an expiration of 120 seconds. 5. A cookie with an session level, valid in browser session.
note
description : "Basic Service that build a generic front to demonstrate the use of Cookies"
date : "$Date$"
revision : "$Revision$"
class
APPLICATION_EXECUTION
inherit
WSF_EXECUTION
create
make
feature -- Basic operations
execute (req: WSF_REQUEST; res: WSF_RESPONSE)
-- Execute the incomming request
local
l_message: STRING
l_header: HTTP_HEADER
l_time: HTTP_DATE
l_cookies: STRING
l_answer: STRING
do
-- all the cookies
create l_cookies.make_empty
across req.cookies as ic loop
l_cookies.append (ic.item.name)
l_cookies.append("<br>")
end
if req.path_info.same_string ("/") then
create l_header.make
create l_answer.make_from_string (web_page)
if req.cookie ("_EWF_Cookie") = Void then
-- First access the the home page, find a cookie with specific name `_EWF_Cookie'
l_answer.replace_substring_all ("$header_title", "Hey, thanks for access our cool site, this is your first acess")
l_answer.replace_substring_all ("$cookies", l_cookies)
create l_time.make_now_utc
l_time.date_time.day_add (40)
l_header.put_cookie_with_expiration_date ("_EWF_Cookie", "EXAMPLE",l_time.date_time, "", Void, False, True)
else
-- No a new access
l_answer.replace_substring_all ("$header_title", "Welcome back, please check all the new things we have!!!")
l_answer.replace_substring_all ("$cookies", l_cookies)
end
l_header.put_content_type_text_html
l_header.put_content_length (l_answer.count)
res.put_header_text (l_header.string)
res.put_string (l_answer)
elseif req.path_info.same_string ("/visitors") then
create l_header.make
create l_answer.make_from_string (visit_page)
if req.cookie ("_visits") = Void then
-- First access the the visit page, find a cookie with specific name `_visits'
l_answer.replace_substring_all ("$visit", "1")
l_answer.replace_substring_all ("$cookies", l_cookies)
create l_time.make_now_utc
l_time.date_time.day_add (40)
l_header.put_cookie_with_expiration_date ("_visits", "1",l_time.date_time, "/visitors", Void, False, True)
else
if attached {WSF_STRING} req.cookie ("_visits") as l_visit then
create l_time.make_now_utc
l_time.date_time.day_add (40)
l_answer.replace_substring_all ("$visit", (l_visit.value.to_integer + 1).out )
l_answer.replace_substring_all ("$cookies", l_cookies)
l_header.put_cookie_with_expiration_date ("_visits", (l_visit.value.to_integer + 1).out,l_time.date_time, "/visitors", Void, False, True)
end
end
create l_time.make_now_utc
l_time.date_time.second_add (120)
l_header.put_content_type_text_html
-- This cookie expires in 120 seconds, its valid for 120 seconds
l_header.put_cookie_with_expiration_date ("_Framework", "EWF",l_time.date_time, "/", Void, False, True)
-- This is a session cookie, valid only to the current browsing session.
l_header.put_cookie ("Session", "Cookie",Void, "/", Void, False, True)
l_header.put_content_length (l_answer.count)
res.add_header_text (l_header.string)
res.put_string (l_answer)
end
end
feature -- Home Page
web_page: STRING = "[
<!DOCTYPE html>
<html>
<head>
<title>EWF Handling Cookies</title>
</head>
<body>
<div class="right">
<h2>$header_title</h2>
</div>
<div class="right">
<a href="/visitors">Visitors</a>
</div>
<div>
<h3>Cookies for the home page</h3>
$cookies
</div>
</body>
</html>
]"
visit_page: STRING = "[
<!DOCTYPE html>
<html>
<head>
<title>EWF Handling Visit Page</title>
</head>
<body>
<div class="right">
<h2>The number of visits is $visit</h2>
</div>
<div>
<h3>Cookies for the Visit page</h3>
$cookies
</div>
</br>
<div>
Back to <a href="/"> Home </a>
</div>
<div id="footer">
<p>EWF Example Cookies</p>
</div>
</body>
</html>
]"
end
Nav: Workbook :: Generating Responses