摘要：背景本人去年在打醬油的時候曾經要求抓過新浪微博的有關數據。然而要讀寫這些微博信息和朋友關系，必須要在新浪圍脖平臺上注冊應用。

本人去年在UCLA打醬油的時候曾經要求抓過新浪微博的有關數據。然而要讀寫這些微博信息和朋友關系，必須要在新浪圍脖平臺上注冊應用。也就是要接觸 OAuth 2.0 這個東西。當時基本不懂，今天看到了阮一峰博客上的這篇文章,決定自己動手一試。

首先，你要把阮一峰博客上的這篇文章 粗略的讀一遍。

然后你要上 新浪開發平臺 注冊一個應用，我注冊的是微連接 - 網頁應用

打開界面你可以看到App Key和App Secret，這是要用的東西

好，接下來下載新浪微博python SDK，我們用Python進行分析

首先，我們先根據微博API上面的HOW-TO 文檔上來做

from weibo import APIClient

APP_KEY = "1234567" # app key
APP_SECRET = "abcdefghijklmn" # app secret
CALLBACK_URL = "http://www.example.com/callback" 
client = APIClient(app_key=APP_KEY, app_secret=APP_SECRET, redirect_uri=CALLBACK_URL)
url = client.get_authorize_url()

這樣就拿到了URL了，你打開這個URL一看，正是提示你要授權應用（出現error:redirect_uri_mismatch 同學請到新浪微博開發界面填好redirect_uri)

好，我們看看源碼

class APIClient(object):
    """
    API client using synchronized invocation.
    """
    def __init__(self, app_key, app_secret, redirect_uri=None, response_type="code", domain="api.weibo.com", version="2"):
        self.client_id = str(app_key)
        self.client_secret = str(app_secret)
        self.redirect_uri = redirect_uri
        self.response_type = response_type
        self.auth_url = "https://%s/oauth2/" % domain
        self.api_url = "https://%s/%s/" % (domain, version)
        self.access_token = None
        self.expires = 0.0
        self.get = HttpObject(self, _HTTP_GET)
        self.post = HttpObject(self, _HTTP_POST)
        self.upload = HttpObject(self, _HTTP_UPLOAD)

    def get_authorize_url(self, redirect_uri=None, **kw):
        """
        return the authorization url that the user should be redirected to.
        """
        redirect = redirect_uri if redirect_uri else self.redirect_uri
        if not redirect:
            raise APIError("21305", "Parameter absent: redirect_uri", "OAuth2 request")
        response_type = kw.pop("response_type", "code")
        return "%s%s?%s" % (self.auth_url, "authorize", 
                _encode_params(client_id = self.client_id, 
                        response_type = response_type, 
                        redirect_uri = redirect, **kw))

client_id,redirect_url,app_key，好熟悉啊，仔細一看，原來是授權碼模式的第一步

  
The client constructs the request URI by adding the following

  parameters to the query component of the authorization endpoint URI

  using the "application/x-www-form-urlencoded" format, per Appendix B:
  
  
response_type

           REQUIRED.  Value MUST be set to "code".
  
  
client_id

           REQUIRED.  The client identifier as described in Section 2.2.
  
  
redirect_uri

           OPTIONAL.  As described in Section 3.1.2.
  
  
scope

           OPTIONAL.  The scope of the access request as described by

           Section 3.3.
  
  
state

           RECOMMENDED.  An opaque value used by the client to maintain

           state between the request and callback.  The authorization

           server includes this value when redirecting the user-agent back

           to the client.  The parameter SHOULD be used for preventing

           cross-site request forgery as described in Section 10.12.

好了，當我們把賬號密碼填寫好了之后驗證成功后，你發現你的瀏覽器上面的URL發生了變化，到底是這么回事呢，請看第二步Authorization Response

  
If the resource owner grants the access request, the authorization

  server issues an authorization code and delivers it to the client by

  adding the following parameters to the query component of the

  redirection URI using the "application/x-www-form-urlencoded" format,

  per Appendix B:
  
  
code

           REQUIRED.  The authorization code generated by the

           authorization server.  The authorization code MUST expire

           shortly after it is issued to mitigate the risk of leaks.  A

           maximum authorization code lifetime of 10 minutes is

           RECOMMENDED.  The client MUST NOT use the authorization code more than once.  If an authorization code is used more than

           once, the authorization server MUST deny the request and SHOULD

           revoke (when possible) all tokens previously issued based on

           that authorization code.  The authorization code is bound to

           the client identifier and redirection URI.
  
  
state

           REQUIRED if the "state" parameter was present in the client

           authorization request.  The exact value received from the

           client.
  
  
For example, the authorization server redirects the user-agent by

  sending the following HTTP response:

 HTTP/1.1 302 Found
 Location: https://client.example.com/cb?code=SplxlOBeZQQYbYS6WxSbIA
           &state=xyz

然后我們繼續按照API的指示做

# 獲取URL參數code:
code = your.web.framework.request.get("code")
r = client.request_access_token(code)

def request_access_token(self, code, redirect_uri=None):
        redirect = redirect_uri if redirect_uri else self.redirect_uri
        if not redirect:
            raise APIError("21305", "Parameter absent: redirect_uri", "OAuth2 request")
        r = _http_post("%s%s" % (self.auth_url, "access_token"), 
                client_id = self.client_id, 
                client_secret = self.client_secret, 
                redirect_uri = redirect, 
                code = code, grant_type = "authorization_code")
        return self._parse_access_token(r)

這個獲得code 方法通?？梢杂泻芏?，但是我們既然是實驗，就手動復制code 吧。

哈哈，很明顯request_access_token 這個方法就是發一個HTTP POST 包嘛

第三步Access Token Request

  
The client makes a request to the token endpoint by sending the

  following parameters using the "application/x-www-form-urlencoded"

  format per Appendix B with a character encoding of UTF-8 in the HTTP

  request entity-body:
  
  
grant_type

           REQUIRED.  Value MUST be set to "authorization_code".
  
  
code

           REQUIRED.  The authorization code received from the

           authorization server.
  
  
redirect_uri

           REQUIRED, if the "redirect_uri" parameter was included in the

           authorization request as described in Section 4.1.1, and their

           values MUST be identical.
  
  
client_id

           REQUIRED, if the client is not authenticating with the

           authorization server as described in Section 3.2.1.
  
  
If the client type is confidential or the client was issued client

  credentials (or assigned other authentication requirements), the

  client MUST authenticate with the authorization server as described

  in Section 3.2.1.
  
  
For example, the client makes the following HTTP request using TLS

  (with extra line breaks for display purposes only):

 POST /token HTTP/1.1
 Host: server.example.com
 Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
 Content-Type: application/x-www-form-urlencoded

 grant_type=authorization_code&code=SplxlOBeZQQYbYS6WxSbIA
 &redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb

最后一步

access_token = r.access_token # 新浪返回的token，類似abc123xyz456
expires_in = r.expires_in # token過期的UNIX時間：http://zh.wikipedia.org/wiki/UNIX%E6%97%B6%E9%97%B4
# TODO: 在此可保存access token
client.set_access_token(access_token, expires_in)

就是從服務器返回的HTTP 包中解析access_token 和 expire_in 數據

同樣來看RFC 文檔中寫的

  
If the access token request is valid and authorized, the

  authorization server issues an access token and optional refresh

  token as described in Section 5.1.  If the request client

  authentication failed or is invalid, the authorization server returns

  an error response as described in Section 5.2.
  
  
An example successful response:

 HTTP/1.1 200 OK
 Content-Type: application/json;charset=UTF-8
 Cache-Control: no-store
 Pragma: no-cache

 {
   "access_token":"2YotnFZFEjr1zCsicMWpAA",
   "token_type":"example",
   "expires_in":3600,
   "refresh_token":"tGzv3JOkF0XG5Qx2TlKWIA",
   "example_parameter":"example_value"
 }

接下來就可以調用API啦~

對于最后兩步看的很累的話，可以自己嘗試寫一個

import urllib, urllib2

APP_KEY = "2613134348"
APP_SECRET = "5a14f41598a7444c7e0dc0422519b091" # app secret
ACCESS_TOKEN = "9cd1b3869e62491331caf444456953e8"
data = {
        "grant_type" : "authorization_code", 
        "code" :ACCESS_TOKEN, 
        "redirect_uri":"http://www.ceclinux.org",
        "client_id":APP_KEY,
        "client_secret":APP_SECRET   
        }
headers = {"host":"api.weibo.com","Authorization":"OAuth2 %s" % ACCESS_TOKEN}
data = urllib.urlencode(data)
request = urllib2.Request("https://api.weibo.com/oauth2/access_token", data, headers)
response = urllib2.urlopen(request)
print response.read()

運行這個文件
最后也能得到一個包含access_token和expire_date的JSON文件

沒了～

http://github.liaoxuefeng.com/sinaweibopy/

https://github.com/michaelliao/sinaweibopy/wiki/OAuth2-HOWTO

http://www.ruanyifeng.com/blog/2014/05/oauth_2_0.html