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HTML Forms, CGI och HTTP. Översikt. Innehåll – Presentation – Beteende HTML Forms (innehåll) CGI (beteende) HTTP (beteende). Webben i bild. HTML. Webbläsare. Webbservrar. HTML-formulär. Forms Tutorials. http://www.w3schools.com/html/html_forms.asp - PowerPoint PPT Presentation
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HTML Forms, CGI och HTTP
Översikt
• Innehåll – Presentation – Beteende
• HTML Forms (innehåll)
• CGI (beteende)
• HTTP (beteende)
Webben i bild
Webbläsare
HTML
Webbservrar
HTML-formulär
Forms Tutorials
• http://www.w3schools.com/html/html_forms.asp
• http://www.ling.gu.se/~lager/kurser/webtechnology/forms.html
CGI i praktiken
The Common Gateway Interface (CGI)
• The task of a web server is to respond to requests from client web browsers by returning output.
• Each time a request is received, the server analyzes what the request asks for, and returns the appropriate output. The two simplest ways, for the server, of doing this are the following:
– if the request identifies a file stored on disk, return the contents of that file;
– if the request identifies an executable command and possibly arguments, run the command and return its output
• CGI defines a standard way of doing the second.
Palindrom-exempel: HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Palindrome Checker</title> </head> <body> <h1>Palindrome Checker</h1> <form action="http://localhost/cgi-bin/palindrome.py"> <p>Enter a word and find out if it's palindrome:</p> <input type="text" name="word" size="20"/> <input type="submit" value="Check"/> </form> </body></html>
Palindrom-exempel : Python
#!/usr/local/bin/python
import cgi
form = cgi.FieldStorage()
word = form["word"].value
print "Content-type: text/html\n\n"
print "<html><body>"if word == word[::-1]: print "<h1>Yes, %s is a palindrome</h1>" %(word,)else: print "<h1>No, %s is not a palindrome</h1>" %(word,)print "</body></html>"
Palindrom-exempel: Prolog
#!/usr/local/bin/plcon -q -g main -s
:- use_module(library(cgi)).
main :- cgi_get_form(Arguments), member(word(Atom),Arguments), atom_chars(Atom,Charlist), format('Content-type: text/html~n~n', []), format("<html><body>"), ( reverse(Charlist,Charlist) -> format("<h1>Yes, ~w is a palindrome!</h1>",[Atom]) ; format("<h1>No, ~w is not a palindrome...</h1>",[Atom]) ), format("</body></html>"), halt.
Installation av CGI-skript på HAL
• Ditt CGI-skript installerar du så här:
1. Skapa ett underbibliotek 'cgi-bin' i ditt www-bibliotek.2. Placera palindrome.py (eller palindrome.pl) i detta bibliotek.3. Byt namnet på filen till 'palindrome.cgi'.4. Kör kommandot chmod a+rx palindrome.cgi för att sätta
nödvändiga läs- och skrivrättigheter.5. Ändra värdet på attributet ’action’ i elementet ’form’ i filen
”palindrome.html” så att det passar din installation.6. Logga in på http://www.cling.gu.se/admin/cgi/ för att aktivera
ditt skript.7. Provkör!
Ditt www-bibliotek
www/ index.html css/ main.css cgi-bin/ palindrome.cgi kurser/ webbteknologi/ index.html ...
Provkörning
file://C:/www/kurser/Webteknologi/webtechnology/cgi_test/palindrome.html
HTTP
HTTP
• Hypertext Transfer Protocol• Webbens kommunikationsprotokoll• Exempel:
Från läsaren till servern (request):
• GET 2004/Talks/0914-tbl-speech/text HTTP/1.1
Från servern till läsaren (response):
• HTTP/1.1 200 OK
<html><body>…</body></html>
Webbläsare
HTML
Webbservrar
Palindrom-exemplet igen…
• Testa i Firefox:
http://localhost/cgi-bin/palindrome.py?word=apa
• Inspektera requests och responses m.h.a. verktyget LiveHTTPHeaders
HTTP request message
GET /cgi-bin/palindrome.py?word=apa HTTP/1.1Host: localhostUser-Agent: Mozilla/5.0 (Windows; U; …Accept: text/xml,application/xml,...Accept-Language: en-us,en;q=0.5Accept-Encoding: gzip,deflateAccept-Charset: ISO-8859-1,utf-8…Keep-Alive: 300Connection: keep-alive
HTTP request message
GET /cgi-bin/palindrome.py?word=apa HTTP/1.1Host: localhostUser-Agent: Mozilla/5.0 (Windows; U; …Accept: text/xml,application/xml,...Accept-Language: en-us,en;q=0.5Accept-Encoding: gzip,deflateAccept-Charset: ISO-8859-1,utf-8…Keep-Alive: 300Connection: keep-alive
Data (if POST is used)
request line (GET, POST,… commands)
requestheaders
extra carriage return, line feed)
query
More about the query
• I webbläsaren:
http://localhost/cgi-bin/palindrome.py?word=apa
• Request (en del av den):
GET /cgi-bin/palindrome.py?word=apa HTTP/1.1
• I CGI-skriptet– Hanteras oftast av ett bibliotek (library) och parsas och översätts
där till en datastruktur där informationen blir lättåtkomlig
More about the query (cont’d)
• Ett sådan bibliotek har en del att göra:
http://www.google.com/search?q=Torbj%C3%B6rn+Lager
http://www.google.com/search?q=Torbj%C3%B6rn+Lager&client=firefox
http://www.google.com/search?q=Torbj%C3%B6rn+Lager&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox
• Det som webbläsaren gör här kallas för “url encoding”
• Så CGI programmet måste alltså utföra “url decoding”
• Tur att man sällan behöver bry sig!!
HTTP response message
HTTP/1.x 200 OKDate: Mon, 18 Feb 2008 08:08:20 GMTServer: Apache/2.0.55 (Win32)Keep-Alive: timeout=15, max=100Connection: Keep-AliveTransfer-Encoding: chunkedContent-Type: text/html
<html><body> <h1>Yes, apa is a palindrome</h1> </body></html>
HTTP response message
HTTP/1.x 200 OKDate: Mon, 18 Feb 2008 08:08:20 GMTServer: Apache/2.0.55 (Win32)Keep-Alive: timeout=15, max=100Connection: Keep-AliveTransfer-Encoding: chunkedContent-Type: text/html
<html><body> <h1>Yes, apa is a palindrome</h1> </body></html>
status line (protocol, status code, status phrase)
responseheaders
data
HTTP response status codes
• A few sample codes:– 200 OK
• request succeeded, requested object later in this message
– 404 Not Found• requested document not found on this server
– 500 Internal Server Error• something is wrong with the server, or (more likely)
with your CGI script
Laborationen
• http://www.ling.gu.se/~lager/kurser/webtechnology/lab3.html
