APIView 类中很最要的一个方法：dispatch
该方法中有两个需要注意的关键点：
- request 替换
- http 请求映射类中的对应名称的方法
def dispatch(self, request, *args, **kwargs):
self.args = args
self.kwargs = kwargs
request = self.initialize_request(request, *args, **kwargs)
self.request = request
self.headers = self.default_response_headers # deprecate?
try:
self.initial(request, *args, **kwargs)
# Get the appropriate handler method
if request.method.lower() in self.http_method_names:
handler = getattr(self, request.method.lower(),
self.http_method_not_allowed)
else:
handler = self.http_method_not_allowed
response = handler(request, *args, **kwargs)
except Exception as exc:
response = self.handle_exception(exc)
self.response = self.finalize_response(request, response, *args, **kwargs)
return self.response
request 替换
以下三段代码将原本Django中的request替换成了新的request，如果需要使用旧的request则需要request._request来获取旧request。
#dispatch方法
request = self.initialize_request(request, *args, **kwargs)
##self.initialize_request
def initialize_request(self, request, *args, **kwargs):
"""
Returns the initial request object.
"""
parser_context = self.get_parser_context(request)
return Request(
request,
parsers=self.get_parsers(),
authenticators=self.get_authenticators(),
negotiator=self.get_content_negotiator(),
parser_context=parser_context
)
#Request类的__init__初始化方法
def __init__(self, request, parsers=None, authenticators=None,
negotiator=None, parser_context=None):
assert isinstance(request, HttpRequest), (
'The `request` argument must be an instance of '
'`django.http.HttpRequest`, not `{}.{}`.'
.format(request.__class__.__module__, request.__class__.__name__)
)
self._request = request
self.parsers = parsers or ()
self.authenticators = authenticators or ()
self.negotiator = negotiator or self._default_negotiator()
self.parser_context = parser_context
self._data = Empty
self._files = Empty
self._full_data = Empty
self._content_type = Empty
self._stream = Empty
if self.parser_context is None:
self.parser_context = {}
self.parser_context['request'] = self
self.parser_context['encoding'] = request.encoding or settings.DEFAULT_CHARSET
force_user = getattr(request, '_force_auth_user', None)
force_token = getattr(request, '_force_auth_token', None)
if force_user is not None or force_token is not None:
forced_auth = ForcedAuthentication(force_user, force_token)
self.authenticators = (forced_auth,)
http 请求映射类中的对应名称的方法
以下代码将 http 方法映射到自己写的 get、post等方法。所以当自己写的类继承自APIView时，只要类中定义了与 http 方法同名的函数，那么当对应的http请求过来的时候，父类中的dispatch方法就会自动进行分发。
if request.method.lower() in self.http_method_names:
handler = getattr(self, request.method.lower(),
self.http_method_not_allowed)
else:
handler = self.http_method_not_allowed
response = handler(request, *args, **kwargs)
具体支持那些 http 方法呢？可以到 generic 下的 base.py 文件下的 View 类中查看：
http_method_names = ['get', 'post', 'put', 'patch', 'delete', 'head', 'options', 'trace']
举个例子：
根据 user agent 来做不同终端的页面渲染，甚至是不同的逻辑（web 和移动端逻辑不同这很正常），这种时候很容易想到重写 dispatch 方法，来做到一种通用的处理方式。
from django.views.generic import View as DjangoView
class View(DjangoView):
def _get_handler(self, request):
'''
根据ua获取handler
'''
handler_name = request.method.lower()
if handler_name in self.http_method_names:
handler = getattr(self, handler_name)
if not handler:
return self.http_method_not_allowed
user_agent = request.META.get('HTTP_USER_AGENT', '').lower()
handler = getattr(self, handler_name, self.http_method_not_allowed)
user_agents = ['ipad', 'iphone', 'ipod', 'androidtv', 'android']
for ua in user_agents:
if ua in user_agent:
handler_name = '{}_{}'.format(handler_name, ua)
break
return getattr(self, handler_name) or handler
def dispatch(self, request, *args, **kwargs):
# Try to dispatch to the right method; if a method doesn't exist,
# defer to the error handler. Also defer to the error handler if the
# request method isn't on the approved list.
# 支持user agent跳转
# 如果实现了对应的方法，则直接使用对应ua的规则
# 例如method=get, ua为iphone的ua，子类实现 get_iphone, 则使用get_iphone进行render
handler = self._get_handler(request)
self.request = request
self.args = args
self.kwargs = kwargs
return handler(request, *args, **kwargs)