def __call__(self, environ, start_response):
        return self.wsgi_app(environ, start_response)

def wsgi_app(self, environ, start_response):
        
        with self.request_context(environ):  #2.1,把环境变量入栈
            rv = self.preprocess_request()   #2.2，请求前的处理操作，主要执行一些函数，主要是准备工作。
            if rv is None:   #请求前如果没有需要做的事情，就会进入到请求分发
                rv = self.dispatch_request()  #2.3 进行请求分发
            response = self.make_response(rv)  #2.4 返回一个response_class的实例对象，也就是可以接受environ和start_reponse两个参数的对象
            response = self.process_response(response)  #2.5 进行请求后的处理操作，只要是执行一些函数，和preprocesses_request()类似，主要是清理工作。
            return response(environ, start_response)   #2.6 对web server（uwsgi）进行正式回应

   def request_context(self, environ):
        
        return _RequestContext(self, environ) #调用_RequestContext（）类

#请求上下文初始化
class _RequestContext(object):
   
    def __init__(self, app, environ):
        self.app = app
        self.url_adapter = app.url_map.bind_to_environ(environ)
        self.request = app.request_class(environ)
        self.session = app.open_session(self.request)
        self.g = _RequestGlobals()
        self.flashes = None
'''
调用with的时候就会执行
'''
    def __enter__(self):
        _request_ctx_stack.push(self)

'''
with进行上下文管理的例子：
with离开后就会执行自定义上下文管理
class Diycontextor:
    def __init__(self,name,mode):
        self.name = name
        self.mode = mode

    def __enter__(self):
        print "Hi enter here!!"
        self.filehander = open(self.name,self.mode)
        return self.filehander

    def __exit__(self,*para):
        print "Hi exit here"
        self.filehander.close()

with Diycontextor('py_ana.py','r') as f:
    for i in f:
        print i
'''
    def __exit__(self, exc_type, exc_value, tb):
       
        if tb is None or not self.app.debug:
            _request_ctx_stack.pop()

class LocalStack(object):

    """This class works similar to a :class:`Local` but keeps a stack
    of objects instead.  This is best explained with an example::
LocalStack类似于Local类，但是它保持了一个栈功能。它能够将对象入栈、出栈，如下：

        >>> ls = LocalStack()
        >>> ls.push(42)
        >>> ls.top
        42
        >>> ls.push(23)
        >>> ls.top
        23
        >>> ls.pop()
        23
        >>> ls.top
        42

    They can be force released by using a :class:`LocalManager` or with
    the :func:`release_local` function but the correct way is to pop the
    item from the stack after using.  When the stack is empty it will
    no longer be bound to the current context (and as such released).
入栈的对象可以通过LocalManage类进行强制释放，或者通过函数release_local函数。但是，正确的姿势是通过pop函数把他们出栈。
当栈为空时，它不再弹出上下文对象，这样就完全释放了。

    By calling the stack without arguments it returns a proxy that resolves to
    the topmost item on the stack.
通过调用调用无参数的stack，返回一个proxy。

   def preprocess_request(self):
       
        for func in self.before_request_funcs:
            rv = func()
            if rv is not None:
                return rv

'''
分发请求
1、获取endpoint和values，即请求url和参数
2、调用视图函数view_functions[endpoint](**values)
3、处理异常错误
'''		
    def dispatch_request(self):
        
        try:
            endpoint, values = self.match_request()
            return self.view_functions[endpoint](**values)
        except HTTPException, e:
            handler = self.error_handlers.get(e.code)
            if handler is None:
                return e
            return handler(e)
        except Exception, e:
            handler = self.error_handlers.get(500)
            if self.debug or handler is None:
                raise
            return handler(e)

    def match_request(self):
        rv = _request_ctx_stack.top.url_adapter.match()
        request.endpoint, request.view_args = rv
        return rv

>>> m = Map([
        ...     Rule('/', endpoint='index'),
        ...     Rule('/downloads/', endpoint='downloads/index'),
        ...     Rule('/downloads/<int:id>', endpoint='downloads/show')
        ... ])
        >>> urls = m.bind("example.com", "/")
        >>> urls.match("/", "GET")
        ('index', {})
        >>> urls.match("/downloads/42")
        ('downloads/show', {'id': 42})

@app.route('/hello')
def hello_world():
    return 'Hello World!'

def make_response(self, rv):
    """Converts the return value from a view function to a real
    response object that is an instance of :attr:`response_class`.

    The following types are allowd for `rv`:

    ======================= ===========================================
    :attr:`response_class`  the object is returned unchanged
    :class:`str`            a response object is created with the
                            string as body
    :class:`unicode`        a response object is created with the
                            string encoded to utf-8 as body
    :class:`tuple`          the response object is created with the
                            contents of the tuple as arguments
    a WSGI function         the function is called as WSGI application
                            and buffered as response object
    ======================= ===========================================

    :param rv: the return value from the view function
    """
    if isinstance(rv, self.response_class):
        return rv
    if isinstance(rv, basestring):
        return self.response_class(rv)
    if isinstance(rv, tuple):
        return self.response_class(*rv)
    return self.response_class.force_type(rv, request.environ)

def after_request(self, f):
        self.after_request_funcs.append(f)
        return f

response = self.make_response(rv)
response = self.process_response(response)

@classmethod
    def force_type(cls, response, environ=None):
"""Enforce that the WSGI response is a response object of the current
        type.  Werkzeug will use the :class:`BaseResponse` internally in many
        situations like the exceptions.  If you call :meth:`get_response` on an
        exception you will get back a regular :class:`BaseResponse` object, even
        if you are using a custom subclass.

        This method can enforce a given response type, and it will also
        convert arbitrary WSGI callables into response objects if an environ
        is provided::

            # convert a Werkzeug response object into an instance of the
            # MyResponseClass subclass.
            response = MyResponseClass.force_type(response)

            # convert any WSGI application into a response object
            response = MyResponseClass.force_type(response, environ)

        This is especially useful if you want to post-process responses in
        the main dispatcher and use functionality provided by your subclass.

        Keep in mind that this will modify response objects in place if
        possible!

def process_response(self, response):
        
        session = _request_ctx_stack.top.session
        if session is not None:
            self.save_session(session, response)
        for handler in self.after_request_funcs:
            response = handler(response)
        return response

# -*- coding: utf-8 -*-
from __future__ import with_statement
import os
import sys
from threading import local
from jinja2 import Environment, PackageLoader, FileSystemLoader
from werkzeug import Request as RequestBase, Response as ResponseBase, \
     LocalStack, LocalProxy, create_environ, cached_property, \
     SharedDataMiddleware
from werkzeug.routing import Map, Rule
from werkzeug.exceptions import HTTPException, InternalServerError
from werkzeug.contrib.securecookie import SecureCookie
from werkzeug import abort, redirect
from jinja2 import Markup, escape

try:
    import pkg_resources
    pkg_resources.resource_stream
except (ImportError, AttributeError):
    pkg_resources = None

#Request继承werkzeug的Request类
class Request(RequestBase):
 
    def __init__(self, environ):
        RequestBase.__init__(self, environ)
        self.endpoint = None
        self.view_args = None
		
#Response继承werkzeug的Response类
class Response(ResponseBase):
    default_mimetype = 'text/html'

#请求的全局变量类
class _RequestGlobals(object):
    pass

#请求上下文初始化
class _RequestContext(object):
   
    def __init__(self, app, environ):
        self.app = app
        self.url_adapter = app.url_map.bind_to_environ(environ)
        self.request = app.request_class(environ)
        self.session = app.open_session(self.request)
        self.g = _RequestGlobals()
        self.flashes = None
'''
调用with的时候就会执行
'''
    def __enter__(self):
        _request_ctx_stack.push(self)

'''
with离开后就会执行
自定义上下文管理
class Diycontextor:
    def __init__(self,name,mode):
        self.name = name
        self.mode = mode

    def __enter__(self):
        print "Hi enter here!!"
        self.filehander = open(self.name,self.mode)
        return self.filehander

    def __exit__(self,*para):
        print "Hi exit here"
        self.filehander.close()

with Diycontextor('py_ana.py','r') as f:
    for i in f:
        print i
'''
    def __exit__(self, exc_type, exc_value, tb):
       
        if tb is None or not self.app.debug:
            _request_ctx_stack.pop()

'''
 self.url_adapter = app.url_map.bind_to_environ(environ)
 >>> m = Map([
        ...     Rule('/', endpoint='index'),
        ...     Rule('/downloads/', endpoint='downloads/index'),
        ...     Rule('/downloads/<int:id>', endpoint='downloads/show')
        ... ])
        >>> urls = m.bind("example.com", "/")
        >>> urls.build("index", {})
        '/'
        >>> urls.build("downloads/show", {'id': 42})
        '/downloads/42'
        >>> urls.build("downloads/show", {'id': 42}, force_external=True)
        'http://example.com/downloads/42'
'''
def url_for(endpoint, **values):
  
    return _request_ctx_stack.top.url_adapter.build(endpoint, values)

'''
flash实现，通过get_flashed_messages获取消息
'''
def flash(message):
   
    session['_flashes'] = (session.get('_flashes', [])) + [message]

def get_flashed_messages():
    
    flashes = _request_ctx_stack.top.flashes
    if flashes is None:
        _request_ctx_stack.top.flashes = flashes = \
            session.pop('_flashes', [])
    return flashes

'''
实现render_template功能，模板名和{content}
'''
def render_template(template_name, **context):
    
    current_app.update_template_context(context)
    return current_app.jinja_env.get_template(template_name).render(context)

'''
实现render_template_string功能，模板名和{content}
'''
def render_template_string(source, **context):
    
    current_app.update_template_context(context)
    return current_app.jinja_env.from_string(source).render(context)

def _default_template_ctx_processor():
   
    reqctx = _request_ctx_stack.top
    return dict(
        request=reqctx.request,
        session=reqctx.session,
        g=reqctx.g
    )

def _get_package_path(name):
    try:
        return os.path.abspath(os.path.dirname(sys.modules[name].__file__))
    except (KeyError, AttributeError):
        return os.getcwd()

'''
Flask类
'''
class Flask(object):

'''
全局变量
'''
    request_class = Request
    response_class = Response
    static_path = '/static'
    secret_key = None
    session_cookie_name = 'session'
    jinja_options = dict(
        autoescape=True,
        extensions=['jinja2.ext.autoescape', 'jinja2.ext.with_']
    )

'''
当前模块名
app=Flask(__name__)

'''
    def __init__(self, package_name):
        self.debug = False
        self.package_name = package_name
        self.root_path = _get_package_path(self.package_name)
        self.view_functions = {}
        self.error_handlers = {}
        self.before_request_funcs = []
        self.after_request_funcs = []
        self.template_context_processors = [_default_template_ctx_processor]
		
        self.url_map = Map()
		
"""
A WSGI middleware that provides static content for development
    environments or simple server setups. Usage is quite simple::

        import os
        from werkzeug.wsgi import SharedDataMiddleware

        app = SharedDataMiddleware(app, {
            '/shared': os.path.join(os.path.dirname(__file__), 'shared')
        })
"""

        if self.static_path is not None:
            self.url_map.add(Rule(self.static_path + '/<filename>',
                                  build_only=True, endpoint='static'))
            if pkg_resources is not None:
                target = (self.package_name, 'static')
            else:
                target = os.path.join(self.root_path, 'static')
            self.wsgi_app = SharedDataMiddleware(self.wsgi_app, {
                self.static_path: target
            })       
        self.jinja_env = Environment(loader=self.create_jinja_loader(),
                                     **self.jinja_options)
        self.jinja_env.globals.update(
            url_for=url_for,
            get_flashed_messages=get_flashed_messages
        )

'''
FileSystemLoader(BaseLoader)
Loads templates from the file system.  This loader can find templates
    in folders on the file system and is the preferred way to load them.

    The loader takes the path to the templates as string, or if multiple
    locations are wanted a list of them which is then looked up in the
    given order::

    >>> loader = FileSystemLoader('/path/to/templates')
    >>> loader = FileSystemLoader(['/path/to/templates', '/other/path'])
	
	 A very basic example for a loader that looks up templates on the file
    system could look like this::

        from jinja2 import BaseLoader, TemplateNotFound
        from os.path import join, exists, getmtime

        class MyLoader(BaseLoader):

            def __init__(self, path):
                self.path = path

            def get_source(self, environment, template):
                path = join(self.path, template)
                if not exists(path):
                    raise TemplateNotFound(template)
                mtime = getmtime(path)
                with file(path) as f:
                    source = f.read().decode('utf-8')
                return source, path, lambda: mtime == getmtime(path)
				
PackageLoader(BaseLoader)
    If the package path is not given, ``'templates'`` is assumed.
	默认值为templates
'''
    def create_jinja_loader(self):
        
        if pkg_resources is None:
            return FileSystemLoader(os.path.join(self.root_path, 'templates'))
        return PackageLoader(self.package_name)

'''
template_context_processors=[dict(
        request=reqctx.request,
        session=reqctx.session,
        g=reqctx.g]
'''
    def update_template_context(self, context):
       
        reqctx = _request_ctx_stack.top
        for func in self.template_context_processors:
            context.update(func())

'''
整体APP启动入口，启动后进行如下几个步骤：
1、判断是否有设置DEBUG
2、运行rum_simple()
app = Flask(__name__)
if __name__ == '__main__():
	app.run()
	
app.run() 
	run_simple(host, port, self, **options) 
	Start a WSGI application. Optional features include a reloader,
    multithreading and fork support.	

'''
    def run(self, host='localhost', port=5000, **options):
       
        from werkzeug import run_simple
        if 'debug' in options:
            self.debug = options.pop('debug')
        options.setdefault('use_reloader', self.debug)
        options.setdefault('use_debugger', self.debug)
        return run_simple(host, port, self, **options)

    def test_client(self):
        
        from werkzeug import Client
        return Client(self, self.response_class, use_cookies=True)

    def open_resource(self, resource):
       
        if pkg_resources is None:
            return open(os.path.join(self.root_path, resource), 'rb')
        return pkg_resources.resource_stream(self.package_name, resource)

    def open_session(self, request):
       
        key = self.secret_key
        if key is not None:
            return SecureCookie.load_cookie(request, self.session_cookie_name,
                                            secret_key=key)

    def save_session(self, session, response):
      
        if session is not None:
            session.save_cookie(response, self.session_cookie_name)

    def add_url_rule(self, rule, endpoint, **options):
       
        options['endpoint'] = endpoint
        options.setdefault('methods', ('GET',))
        self.url_map.add(Rule(rule, **options))


'''
@app.route('/test')
def test():
	pass
	
route是一个装饰器，它干了2个事情：
1、添加url到map里
2、添加函数名到视图函数{'test':test}
'''
    def route(self, rule, **options):
        
        def decorator(f):
            self.add_url_rule(rule, f.__name__, **options)
            self.view_functions[f.__name__] = f
            return f
        return decorator

'''
A decorator that is used to register a function give a given
        error code.  Example::

            @app.errorhandler(404)
            def page_not_found():
                return 'This page does not exist', 404

        You can also register a function as error handler without using
        the :meth:`errorhandler` decorator.  The following example is
        equivalent to the one above::

            def page_not_found():
                return 'This page does not exist', 404
            app.error_handlers[404] = page_not_found
			
			error_handlers = {page_not_found:404}

'''	
    def errorhandler(self, code):
       
        def decorator(f):
            self.error_handlers[code] = f
            return f
        return decorator
'''
请求开始前做准备工作，比如数据库连接，用户验证
@app.before_request  
def before_request():  
    #可在此处检查jwt等auth_key是否合法，  
    #abort(401)  
    #然后根据endpoint，检查此api是否有权限，需要自行处理  
    #print(["endpoint",connexion.request.url_rule.endpoint])  
    #abort(401)  
    #也可做ip检查，以阻挡受限制的ip等   
'''
    def before_request(self, f):
        
        self.before_request_funcs.append(f)
        return f

    def after_request(self, f):
        self.after_request_funcs.append(f)
        return f

    def context_processor(self, f):
        self.template_context_processors.append(f)
        return f
'''
 Here is a small example for matching:

        >>> m = Map([
        ...     Rule('/', endpoint='index'),
        ...     Rule('/downloads/', endpoint='downloads/index'),
        ...     Rule('/downloads/<int:id>', endpoint='downloads/show')
        ... ])
        >>> urls = m.bind("example.com", "/")
        >>> urls.match("/", "GET")
        ('index', {})
        >>> urls.match("/downloads/42")
        ('downloads/show', {'id': 42})
'''
    def match_request(self):
        rv = _request_ctx_stack.top.url_adapter.match()
        request.endpoint, request.view_args = rv
        return rv
		
'''
分发请求
1、获取endpoint和values，即请求url和参数
2、调用视图函数view_functions[endpoint](**values)
3、处理异常错误
'''		
    def dispatch_request(self):
        
        try:
            endpoint, values = self.match_request()
            return self.view_functions[endpoint](**values)
        except HTTPException, e:
            handler = self.error_handlers.get(e.code)
            if handler is None:
                return e
            return handler(e)
        except Exception, e:
            handler = self.error_handlers.get(500)
            if self.debug or handler is None:
                raise
            return handler(e)
'''
from werkzeug.wrappers import BaseResponse as Response

        def index():
            return Response('Index page')

        def application(environ, start_response):
            path = environ.get('PATH_INFO') or '/'
            if path == '/':
                response = index()
            else:
                response = Response('Not Found', status=404)
            return response(environ, start_response)
'''
    def make_response(self, rv):
      
        if isinstance(rv, self.response_class):
            return rv
        if isinstance(rv, basestring):
            return self.response_class(rv)
        if isinstance(rv, tuple):
            return self.response_class(*rv)
        return self.response_class.force_type(rv, request.environ)

    def preprocess_request(self):
       
        for func in self.before_request_funcs:
            rv = func()
            if rv is not None:
                return rv

    def process_response(self, response):
        
        session = _request_ctx_stack.top.session
        if session is not None:
            self.save_session(session, response)
        for handler in self.after_request_funcs:
            response = handler(response)
        return response

    def wsgi_app(self, environ, start_response):
        
        with self.request_context(environ):
            rv = self.preprocess_request()
            if rv is None:
                rv = self.dispatch_request()
            response = self.make_response(rv)
            response = self.process_response(response)
            return response(environ, start_response)

    def request_context(self, environ):
        
        return _RequestContext(self, environ)

    def test_request_context(self, *args, **kwargs):
       
        return self.request_context(create_environ(*args, **kwargs))
'''
app=Flask(__name__)

call(self, environ, start_response) 
			wsgi_app(self, environ, start_response) 
			wsgi_app是flask核心:

'''
    def __call__(self, environ, start_response):
        return self.wsgi_app(environ, start_response)

# context locals
_request_ctx_stack = LocalStack()
current_app = LocalProxy(lambda: _request_ctx_stack.top.app)
request = LocalProxy(lambda: _request_ctx_stack.top.request)
session = LocalProxy(lambda: _request_ctx_stack.top.session)
g = LocalProxy(lambda: _request_ctx_stack.top.g)