Api消息參數(shù)的傳遞

在服務(wù)啟動之后春缕，WSGIServer就開始在監(jiān)聽client的請求了
注：關(guān)于服務(wù)的啟動悦陋，在前面幾篇文檔中已有詳細說明么鹤，請移步查看那各app是如何獲取到請求的相關(guān)參數(shù)的呢案狠？比如策略的創(chuàng)建：

@parameter_checker.is_valid_body(dj_constants.SERVICES)
def create(self, req, **kwargs):
    """
    create a service
    :param req:
    :param kwargs:
    :return:
    """
    context = req.environ['test.context']
    services = objects.PlanList.get_all_by_project(context,
                                                   context.project_id,
                                                   None, None)

這就涉及到plan app的注冊過程
在router.py的APIRouter中磕昼，mapper中plan對應(yīng)的controller是resource類型的對象

class APIRouter(wsgi_common.Router):
    @classmethod
    def factory(cls, global_conf, **local_conf):
        return cls(ProjectMapper())

    def __init__(self, mapper):
        plans_resources = plans.create_resource()

可以看到create_resource()方法返回的是一個wsgi.py的Resource對象卷雕，而Resource類又繼承自wsgi.py的Application類，Resource實現(xiàn)了Application的__call__方法票从，這個方法會在對象調(diào)用的時候被自動執(zhí)行

def __call__(self, request):
    """WSGI method that controls (de)serialization and method dispatch."""

    LOG.info(_LI("%(method)s %(url)s"),
             {"method": request.method,
              "url": request.url})

    # Identify the action, its arguments, and the requested
    # content type
    action_args = self.get_action_args(request.environ)
    action = action_args.pop('action', None)
    content_type, body = self.get_body(request)
    accept = request.best_match_content_type()

    # NOTE(Vek): Splitting the function up this way allows for
    #            auditing by external tools that wrap the existing
    #            function.  If we try to audit __call__(), we can
    #            run into troubles due to the @webob.dec.wsgify()
    #            decorator.
    return self._process_stack(request, action, action_args,
                               content_type, body, accept)

該方法通過解析request漫雕，得到當前請求的http字段（content_type，method類型峰鄙，body等）浸间，_process_stack方法如下

def _process_stack(self, request, action, action_args,
                   content_type, body, accept):
    """Implement the processing stack."""

    # Get the implementing method
    try:
        meth, extensions = self.get_method(request, action,
                                           content_type, body)
	…
# Now, deserialize the request body...
    try:
        if content_type:
            contents = self.deserialize(meth, content_type, body)
        else:
            contents = {}
	…
    # Update the action args
    action_args.update(contents)

    project_id = action_args.pop("project_id", None)
    context = request.environ.get('test.context')
    if (context and project_id and (project_id != context.project_id)):
        msg = _("Malformed request url")
        return Fault(webob.exc.HTTPBadRequest(explanation=msg))

    # Run pre-processing extensions
    response, post = self.pre_process_extensions(extensions,       

meth為從控制器中根據(jù)action的值獲取相應(yīng)的方法（例如：cinder.api.v1.volumes.VolumeController.create）；extensions為根據(jù)控制器和action的值獲取相應(yīng)的擴展方法吟榴；

def pre_process_extensions(self, extensions, request, action_args):
    # List of callables for post-processing extensions
    post = []

    for ext in extensions:
        if inspect.isgeneratorfunction(ext):
            response = None

            # If it's a generator function, the part before the
            # yield is the preprocessing stage
            try:
                with ResourceExceptionHandler():
                    gen = ext(req=request, **action_args)
                    response = next(gen)
            except Fault as ex:
                response = ex

            # We had a response...
            if response:
                return response, []

上面的代碼中魁蒜，其中ext就是實際調(diào)用的方法名，可以發(fā)現(xiàn)ext(req=request, **action_args)吩翻，最終是從這里將業(yè)務(wù)方法的參數(shù)傳遞進去的

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github：https://github.com/tunsuy