Django接收自定义http header过程详解

框架(架构)  /  管理员 发布于 7年前   255

add by zhj: Django将所有http header（包括你自定义的http header）都放在了HttpRequest.META这个Python标准字典中，当然HttpRequest.META

中还包含其它一些键值对，这些键值对是Django加进去的，如SERVER_PORT等。对于http header，Django进行了重命名，规则如下

(1) 所有header名大写，将连接符“-”改为下划线“_”

(2) 除CONTENT_TYPE和CONTENT_LENGTH，其它的header名称前加“HTTP_”前缀

参见 https://docs.djangoproject.com/en/1.6/ref/request-response/#django.http.HttpRequest.META

我个人比较喜欢跟踪源代码来查看，源代码如下，

class WSGIRequestHandler(BaseHTTPRequestHandler):  server_version = "WSGIServer/" + __version__  def get_environ(self):    env = self.server.base_environ.copy()    env['SERVER_PROTOCOL'] = self.request_version    env['REQUEST_METHOD'] = self.command    if '?' in self.path:      path,query = self.path.split('?',1)    else:      path,query = self.path,''    env['PATH_INFO'] = urllib.unquote(path)    env['QUERY_STRING'] = query    host = self.address_string()    if host != self.client_address[0]:      env['REMOTE_HOST'] = host    env['REMOTE_ADDR'] = self.client_address[0]    if self.headers.typeheader is None:      env['CONTENT_TYPE'] = self.headers.type    else:      env['CONTENT_TYPE'] = self.headers.typeheader    length = self.headers.getheader('content-length')    if length:      env['CONTENT_LENGTH'] = length    for h in self.headers.headers:      k,v = h.split(':',1)      k=k.replace('-','_').upper(); v=v.strip()      if k in env:        continue          # skip content length, type,etc.      if 'HTTP_'+k in env:        env['HTTP_'+k] += ','+v   # comma-separate multiple headers      else:        env['HTTP_'+k] = v    return env  def get_stderr(self):    return sys.stderr  def handle(self):    """Handle a single HTTP request"""    self.raw_requestline = self.rfile.readline()    if not self.parse_request(): # An error code has been sent, just exit      return    handler = ServerHandler(      self.rfile, self.wfile, self.get_stderr(), self.get_environ()    )    handler.request_handler = self   # backpointer for logging    handler.run(self.server.get_app())

class WSGIRequest(http.HttpRequest):  def __init__(self, environ):    script_name = base.get_script_name(environ)    path_info = base.get_path_info(environ)    if not path_info:      # Sometimes PATH_INFO exists, but is empty (e.g. accessing      # the SCRIPT_NAME URL without a trailing slash). We really need to      # operate as if they'd requested '/'. Not amazingly nice to force      # the path like this, but should be harmless.      path_info = '/'    self.environ = environ    self.path_info = path_info    self.path = '%s/%s' % (script_name.rstrip('/'), path_info.lstrip('/'))    self.META = environ    self.META['PATH_INFO'] = path_info    self.META['SCRIPT_NAME'] = script_name    self.method = environ['REQUEST_METHOD'].upper()    _, content_params = self._parse_content_type(self.META.get('CONTENT_TYPE', ''))    if 'charset' in content_params:      try:        codecs.lookup(content_params['charset'])      except LookupError:        pass      else:        self.encoding = content_params['charset']    self._post_parse_error = False    try:      content_length = int(self.environ.get('CONTENT_LENGTH'))    except (ValueError, TypeError):      content_length = 0    self._stream = LimitedStream(self.environ['wsgi.input'], content_length)    self._read_started = False    self.resolver_match = None

WSGIRequest类实例化方法__init__(self,environ)中第二个参数就是WSGIRequestHandler.get_environ()方法返回的数据

WSGIRequest.META在environ的基础上加了一些键值对

用Django做后台，客户端向Django请求数据，为了区分不同的请求，想把每个请求类别加在HTTP头部（headers）里面。

先做实验，就用Python的httplib库来做模拟客户端，参考网上写出模拟代码如下：

#coding=utf8import httplibhttpClient = Nonetry:  myheaders = { "category": "Books",         "id": "21",         'My-Agent': "Super brower"       }  httpClient = httplib.HTTPConnection('10.14.1XX.XXX',8086,timeout=30)  httpClient.request('GET','/headinfo/',headers=myheaders)  response = httpClient.getresponse()  print response.status  print response.reason  print response.read()except Exception, e:  print efinally:  if httpClient:    httpClient.close()

其中'/headinfo/'为服务器的响应目录。

然后是服务端的响应代码，《The Django Book》第七章有个获取META的例子：

# GOOD (VERSION 2)def ua_display_good2(request):  ua = request.META.get('HTTP_USER_AGENT', 'unknown')  return HttpResponse("Your browser is %s" % ua)

正好看过这个例子，就模拟上面的这个写了一个能够返回客户端自定义头部的模块：

from django.http import HttpResponsedef headinfo(request):  category = request.META.get('CATEGORY', 'unkown')  id = request.META.get('ID','unkown')  agent = request.META.get('MY-AGENT','unkown')  html = "<html><body>Category is %s, id is %s, agent is %s</body></html>" % (category, id, agent)  return HttpResponse(html)

运行结果如下：

$python get.py#输出:#200#OK#<html><body>Category is unkown, id is unkown, agent is unkown</body></html>

可以看到服务器成功响应了，但是却没有返回自定义的内容。

我以为是客户端模拟headers出问题了，查找和试验了许多次都没有返回正确的结果。后来去查Django的文档，发现了相关的描述：

HttpRequest.META

A standard Python dictionary containing all available HTTP headers. Available headers depend on the client and server, but here are some examples:

• CONTENT_LENGTH C the length of the request body (as a string).
• CONTENT_TYPE C the MIME type of the request body.
• HTTP_ACCEPT_ENCODING C Acceptable encodings for the response.
• HTTP_ACCEPT_LANGUAGE C Acceptable languages for the response.
• HTTP_HOST C The HTTP Host header sent by the client.
• HTTP_REFERER C The referring page, if any.
• HTTP_USER_AGENT C The client's user-agent string.
• QUERY_STRING C The query string, as a single (unparsed) string.
• REMOTE_ADDR C The IP address of the client.
• REMOTE_HOST C The hostname of the client.
• REMOTE_USER C The user authenticated by the Web server, if any.
• REQUEST_METHOD C A string such as "GET" or "POST".
• SERVER_NAME C The hostname of the server.
• SERVER_PORT C The port of the server (as a string).

With the exception of CONTENT_LENGTH and CONTENT_TYPE, as given above, any HTTP headers in the request are converted toMETA keys by converting all characters to uppercase, replacing any hyphens with underscores and adding an HTTP_ prefix to the name. So, for example, a header called X-Bender would be mapped to the META key HTTP_X_BENDER.

其中红色的部分说明是说除了两个特例之外，其他的头部在META字典中的key值都会被加上“HTTP_”的前缀，终于找到问题所在了，赶紧修改服务端代码：

category = request.META.get('HTTP_CATEGORY', 'unkown')id = request.META.get('HTTP_ID','unkown')

果然，执行后返回了想要的结果：

$python get.py#正确的输出：#200#OK#<html><body>Category is Books, id is 21, agent is Super brower</body></html>

得到的经验就是遇到问题要多查文档，搜索引擎并不一定比文档更高效。

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