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 = NoneWSGIRequest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 the length of the request body (as a string).
- CONTENT_TYPE the MIME type of the request body.
- HTTP_ACCEPT_ENCODING Acceptable encodings for the response.
- HTTP_ACCEPT_LANGUAGE Acceptable languages for the response.
- HTTP_HOST The HTTP Host header sent by the client.
- HTTP_REFERER The referring page, if any.
- HTTP_USER_AGENT The client's user-agent string.
- QUERY_STRING The query string, as a single (unparsed) string.
- REMOTE_ADDR The IP address of the client.
- REMOTE_HOST The hostname of the client.
- REMOTE_USER The user authenticated by the Web server, if any.
- REQUEST_METHOD A string such as "GET" or "POST".
- SERVER_NAME The hostname of the server.
- SERVER_PORT 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。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持武林网。
新闻热点
疑难解答
图片精选
