这是我参与11月更文挑战的第10天，活动详情查看：2021最后一次更文挑战
一、源码剖析
和认证流程一样，请求进来，同样走APIview的dispatch的方法，请阅读注解部分：
1.APIView类的dispatch源码：
def dispatch(self, request, *args, **kwargs):
"""
`.dispatch()` is pretty much the same as Django's regular dispatch,
but with extra hooks for startup, finalize, and exception handling.
"""
self.args = args
self.kwargs = kwargs
#对原始request进行加工，丰富了一些功能#Request(# request,# parsers=self.get_parsers(),# authenticators=self.get_authenticators(),# negotiator=self.get_content_negotiator(),# parser_context=parser_context# )#request(原始request,[BasicAuthentications对象，])#获取原生request,request._request#获取认证类的对象，request.authticators#1.封装request
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 methodif 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
2.接着执行self.inital方法：
def initial(self, request, *args, **kwargs):
"""
Runs anything that needs to occur prior to calling the method handler.
"""
self.format_kwarg = self.get_format_suffix(**kwargs)
# Perform content negotiation and store the accepted info on the request
neg = self.perform_content_negotiation(request)
request.accepted_renderer, request.accepted_media_type = neg
# Determine the API version, if versioning is in use.####版本控制
version, scheme = self.determine_version(request, *args, **kwargs)
request.version, request.versioning_scheme = version, scheme
# Ensure that the incoming request is permitted#2.实现认证 self.perform_authentication(request)
#3.权限判断 self.check_permissions(request)
#4.频率限制
self.check_throttles(request)
3.可以看到版本控制是在认证之前，首先下执行version, scheme = self.determine_version(request, *args, **kwargs)，以下是self.determine_version源码：
def determine_version(self, request, *args, **kwargs):
"""
If versioning is being used, then determine any API version for the
incoming request. Returns a two-tuple of (version, versioning_scheme)
"""if self.versioning_class is None: #先判断版本类是否存在(self.versioning_class 是否为存在)，不存在返回tuple，（none,none）
return (None, None)
scheme = self.versioning_class() #存在返回版本类对象
return (scheme.determine_version(request, *args, **kwargs), scheme) #版本类存在，最后返回版本类对象的determine_version方法结果（也就是返回的版本号），和类对象，
这也就是每个版本类必须要有的方法，用来获取版本。
4.承接 self.determine_version方法执行完成以后，接着执行request.version, request.versioning_scheme = version, scheme，这个不用多说，无非将版本号赋值给request.version属性，版本类对象赋值给request.versioning_scheme,这也就是我们为什么能通过request.version获取版本号的原因。
5.同认证源码一样，self.determine_version方法中使用的版本类self.versioning_class()，在全局中也有配置
class APIView(View):
# The following policies may be set at either globally, or per-view.
renderer_classes = api_settings.DEFAULT_RENDERER_CLASSES
parser_classes = api_settings.DEFAULT_PARSER_CLASSES
authentication_classes = api_settings.DEFAULT_AUTHENTICATION_CLASSES
throttle_classes = api_settings.DEFAULT_THROTTLE_CLASSES
permission_classes = api_settings.DEFAULT_PERMISSION_CLASSES
content_negotiation_class = api_settings.DEFAULT_CONTENT_NEGOTIATION_CLASS
metadata_class = api_settings.DEFAULT_METADATA_CLASS
versioning_class = api_settings.DEFAULT_VERSIONING_CLASS #版本处理类配置
6.基于以上源码分析完成以后，下面我们来剖析下，我们示例中所使用的两个版本处理类，具体分析请看注解：
QueryParameterVersioning(BaseVersioning)
class QueryParameterVersioning(BaseVersioning):
"""
GET /something/?version=0.1 HTTP/1.1
Host: example.com
Accept: application/json
"""
invalid_version_message = _('Invalid version in query parameter.') ## 当setting.py配置了允许的版本时候，不匹配版本返回的错误信息，可以自己定义
def determine_version(self, request, *args, **kwargs): ## 获取版本方法
version = request.query_params.get(self.version_param, self.default_version) # 通过request.query_paras方法获取（本质request.MATE.get），
default_version默认是version，是在settings中配置的
if not self.is_allowed_version(version): #不允许的版本抛出异常
raise exceptions.NotFound(self.invalid_version_message)
return version #无异常则返回版本号
def reverse(self, viewname, args=None, kwargs=None, request=None, format=None, **extra): #url 反解析，可以通过该方法生成请求的url，后面会有示例
url = super(QueryParameterVersioning, self).reverse(
viewname, args, kwargs, request, format, **extra
)
if request.version is not None:
return replace_query_param(url, self.version_param, request.version)
return url
URLPathVersioning
class URLPathVersioning(BaseVersioning):
"""
To the client this is the same style as `NamespaceVersioning`.
The difference is in the backend - this implementation uses
Django's URL keyword arguments to determine the version.
An example URL conf for two views that accept two different versions.
urlpatterns = [
url(r'^(?P<version>[v1|v2]+)/users/$', users_list, name='users-list'),
url(r'^(?P<version>[v1|v2]+)/users/(?P<pk>[0-9]+)/$', users_detail, name='users-detail')
]
GET /1.0/something/ HTTP/1.1
Host: example.com
Accept: application/json
"""
invalid_version_message = _('Invalid version in URL path.') # 不允许的版本信息，可定制
def determine_version(self, request, *args, **kwargs): ## 同样实现determine_version方法获取版本
version = kwargs.get(self.version_param, self.default_version) # 由于传递的版本在url的正则中，所以从kwargs中获取，self.version_param默认是version
if not self.is_allowed_version(version):
raise exceptions.NotFound(self.invalid_version_message) # 没获取到，抛出异常
return version # 正常获取，返回版本号
def reverse(self, viewname, args=None, kwargs=None, request=None, format=None, **extra): # url反解析，后面会有示例
if request.version is not None:
kwargs = {} if (kwargs is None) else kwargs
kwargs[self.version_param] = request.version
return super(URLPathVersioning, self).reverse(
viewname, args, kwargs, request, format, **extra
这个版本类都继承了BaseVersioning：
class BaseVersioning(object):
default_version = api_settings.DEFAULT_VERSION #默默人版本配置
allowed_versions = api_settings.ALLOWED_VERSIONS #允许版本配置
version_param = api_settings.VERSION_PARAM #版本key配置
def determine_version(self, request, *args, **kwargs):
msg = '{cls}.determine_version() must be implemented.'raise NotImplementedError(msg.format(
cls=self.__class__.__name__
))
def reverse(self, viewname, args=None, kwargs=None, request=None, format=None, **extra):
return _reverse(viewname, args, kwargs, request, format, **extra)
def is_allowed_version(self, version):
if not self.allowed_versions:
return True
return ((version is not None and version == self.default_version) or
(version in self.allowed_versions))
二、利用版本反向生成URL
以URLPathVersioning为例，其本质也是用的django的url反向解析方法，实现过程这里就不用过多说明，有兴趣可以自己看源码。
1.配置url，为view取别名
urlpatterns = [
url(r'^api/v1/auth', views.AuthView.as_view()),
url(r'^api/v1/order', views.OrderView.as_view()),
url(r'^api/(?P<version>[v1|v2]+)/user', views.UserView.as_view(),name="user_view"),
]
2.利用reverse方法反向生成请求的url,UserView视图。
class UserView(APIView):
'''查看用户信息'''from rest_framework.versioning import URLPathVersioning
versioning_class =URLPathVersioning
def get(self,request,*args,**kwargs):
print(request.version)
url = request.versioning_scheme.reverse(viewname='user_view', request=request)
#versioning_scheme已经在源码中分析过了，就是版本类实例化的对象print(url)
res={"name":"wd","age":22}
return JsonResponse(res,safe=True)
使用postman发请求：http://127.0.0.1:8000/api/v1/user查看结果如下：
三 、总结
对于版本控制来说，其实没必要自己去定义或自己写版本处理的类，推荐使用全局配置，以及URLPathVersioning类。
具体配置：
# 全局配置
REST_FRAMEWORK = {
"DEFAULT_VERSIONING_CLASS":"rest_framework.versioning.URLPathVersioning", #类的路径"DEFAULT_VERSION":'v1', #默认的版本"ALLOWED_VERSIONS":['v1','v2'], #允许的版本 # "VERSION_PARAM":'version' #使用QueryParameterVersioning时候进行的配置，get请求时候传递的参数的key }
#单一视图
versioning_class =URLPathVersioning
