[python]use cookie to handle http 302 post redirection....

Two pages:

Page A: login page, POST method is used.

Page B: query page, GET method is used.

If directly send a GET request to Page B, you will be redirected to Page A with 302 response.

Task : find a way to handle the redirection and get response from Page B.

Trials :

1. If we first login page A, then use the same connection to send GET request to page B.  But this method is not feasible . When sending GET request to page B, it is reponsed with 302 redirection to page A again. This is due to HTTP protocal is stateless . The login information can't be persisted for page B to use.

So this method is not feasible.

2. Can we rely on python's own Python HTTPRedirectHandler ? Directly accessing Page B, let python handle the redirection response? No. This method is also not feasible .

According to Python HTTPRedirectHandler the redirect handler will take the request and convert it from POST to GET and follow the 301 or 302.  Login page A requires a POST method, so we can't use it.

Solution :

Use cookie to save the login.

This solution is very simple, just three lines code.

cj=cookielib.LWPCookieJar() opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(cj)) urllib2.install_opener(opener)

The whole sample code is as below, the code is self-explained.

import urllib,urllib2, httplib,cookielib httplib.HTTPConnection.debuglevel = 1 #Login POST data params = urllib.urlencode({'username': 'bettermanlu'}) #print params #save the login information into a cookie, otherwise when calling hash query, you will be redirected to the login page again. cj=cookielib.LWPCookieJar() opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(cj)) urllib2.install_opener(opener) #call login page f = opener.open("http://sample.com/login/",params) #print f.info() #now calling each query page for your request. request=urllib2.Request("http://sample.com/subquery/44D88612FEA8A8F36DE82E1278ABB02F") f = opener.open(request) print f.read() #f.read() use "GET" method to get the response from server.

Ref:

http://bugs.python.org/issue1401