django源碼閱讀

時間 2019-12-12

標籤 django 源碼閱讀欄目 Python 简体版

原文原文鏈接

最近再看django-bootstrap-toolkit,一直困惑於靜態文件的路徑問題。因此只能從源碼入手了。
從manage.py開始。
manage.py 比較簡單就幾句話。python

#!/usr/bin/env python
#from django.core.management import execute_manager
import os
import sys 


if __name__ == "__main__":
    #加載配置文件
    os.environ.setdefault("DJANGO_SETTINGS_MODULE","settings")

    from django.core.management import execute_from_command_line
    #執行配置
    execute_from_command_line(sys.argv)

首先看os.environ.setdefault(),environ爲類_Environ的一個實例，它繼承自IterableUserDict，而IterableUserDict繼承自UserDict，包括setdefault()這個方法也是UserDict的一個方法，看一下setdefault實現的功能：git

def setdefault(self, key, failobj=None):
    if key not in self:
        self[key] = failobj
    return self[key]

其中的key是 DJANGO_SETTINGS_MODULE，這裏的self是一個字典，判斷key是否是在裏面，不在裏面就作一個鍵值綁定。而後返回。django

下面進入execute_from_command_line(sys.argv)，sys.argv位一個參數執行的列表，像咱們執行python manage.py runserver時，manage.py位sys.argv[0],runserver爲sys.argv[1],以此類推，若是有更多參數加的話。bootstrap

進入django的core模塊下，找到management模塊。在__init__.py下能夠找到該函數cookie

def execute_from_command_line(argv=None):
    """ 
    A simple method that runs a ManagementUtility.
    """
    utility = ManagementUtility(argv)
    utility.execute()

咱們輸入的參數便傳到了這個函數裏，其中ManagementUtility位一個類穿進去的參數列表會進入一個簡單的初始化網絡

def __init__(self, argv=None):
    self.argv = argv or sys.argv[:]
    self.prog_name = os.path.basename(self.argv[0])

將參數列表賦給argv，而後返回sys.argv[0]的文件名字給prog_name。
實例化完了以後，再看utility.execute()即類ManagementUtility的execute（）方法。多線程

parser = LaxOptionParser(usage="%prog subcommand [options] [args]",
                                    version=get_version(),
                                    option_list=BaseCommand.option_list)
        self.autocomplete()
        try:
            options, args = parser.parse_args(self.argv)
            handle_default_options(options)
        except:
            pass # Ignore any option errors at this point.

        try:
            subcommand = self.argv[1]
        except IndexError:
            subcommand = 'help' # Display help if no arguments were given.

        if subcommand == 'help':

                if len(args) <= 2:
                    parser.print_lax_help()
                    sys.stdout.write(self.main_help_text() + '\n')
                elif args[2] == '--commands':
                    sys.stdout.write(self.main_help_text(commands_only=True) + '\n')
                else:
                    self.fetch_command(args[2]).print_help(self.prog_name, args[2])
        elif subcommand == 'version':
            sys.stdout.write(parser.get_version() + '\n')
        # Special-cases: We want 'django-admin.py --version' and
        # 'django-admin.py --help' to work, for backwards compatibility.
        elif self.argv[1:] == ['--version']:
        # LaxOptionParser already takes care of printing the version.
            pass
        elif self.argv[1:] in (['--help'], ['-h']):
            parser.print_lax_help()
            sys.stdout.write(self.main_help_text() + '\n')
        else:
            self.fetch_command(subcommand).run_from_argv(self.argv)

第一個語句爲詞法分析，但是找遍了LaxOptionParser這個類也沒有找到入口，裏面並無init,只有幾個函數，但是python也沒有正式的構造函數重載的什麼的，後來發現此類繼承自OptionParser這個類，它來自於optparse模塊，在OptionParser模塊裏有一個init()函數，會接受若干個參數，進行初始化，這裏只是傳遞了3個參數，usage傳遞了一個字符串，version爲版本，BaseCommand.option_list爲一個關於命令行的元組，其中調用了make_option這個類init進行一些初始化，主要初始化_short_opts和_long_opts這兩個參數，而且進行了一些檢查。_short_opts爲短命令，_long_opts爲長命令，如-h，--help分別爲短命令和長命令。
parser爲LaxOptionParser的一個實例。 parser.parse_args(self.argv)這個函數會根據上面初始化的內容進行解析命令行參數，以後返回兩個值：options，它是一個對象（，保存有命令行參數值。只要知道命令行參數名，如 file，就能夠訪問其對應的值： options.file 。args，它是一個由 positional arguments 組成的列表。app

def handle_default_options(options):
    """ 
    Include any default options that all commands should accept here
    so that ManagementUtility can handle them before searching for
    user commands.

    """
        if options.settings:
            os.environ['DJANGO_SETTINGS_MODULE'] = options.settings
        if options.pythonpath:
            sys.path.insert(0, options.pythonpath)

handle_default_options將解析出來的options對象當作參數，判斷settings和pythonpath是否存在，而後
設置環境變量和python模塊的搜索路徑。socket

接下來是得到命令行的命令參數self.argv[1],並判斷這個命令，包括錯誤處理，是否時help，是不是version，根據不一樣的狀況展現不一樣的信息。ide

最重要的是最後一句，即前面的狀況都不是，就進入self.fetch_command(subcommand).run_from_argv(self.argv)

def fetch_command(self, subcommand):
    """
    Tries to fetch the given subcommand, printing a message with the
    appropriate command called from the command line (usually
    "django-admin.py" or "manage.py") if it can't be found.
    """
    # Get commands outside of try block to prevent swallowing exceptions
    commands = get_commands()
    try:
        app_name = commands[subcommand]
    except KeyError:
        sys.stderr.write("Unknown command: %r\nType '%s help' for usage.\n" %
            (subcommand, self.prog_name))
        sys.exit(1)
    if isinstance(app_name, BaseCommand):
        # If the command is already loaded, use it directly.
        klass = app_name
    else:
        klass = load_command_class(app_name, subcommand)
    return klass

得到django/core/management/commands目錄下與INSTALLED_APPS/management/commands目錄下的子命令對應的模塊前綴

def load_command_class(app_name, name):
    """
    Given a command name and an application name, returns the Command
    class instance. All errors raised by the import process
    (ImportError, AttributeError) are allowed to propagate.
    """
    module = import_module('%s.management.commands.%s' % (app_name, name))
    return module.Command()

返回Command類的實例。進入management/commands下進入每一個文件會發現，每一個都有Command類對應相應的命令。

self.fetch_command(subcommand).run_from_argv(self.argv)找到咱們輸入的命令參數，而且使用run_from_argv執行。

進入runserver這個命令下看一下，Command這個類繼承了BaseCommand這個類，BaseCommand在Base.py中，裏面有run_from_arv這個方法，在其餘的命令裏
有的重寫了這個方法，不過runserver沒有。

def run_from_argv(self, argv):
    """
    Set up any environment changes requested (e.g., Python path
    and Django settings), then run this command. If the
    command raises a ``CommandError``, intercept it and print it sensibly
    to stderr. If the ``--traceback`` option is present or the raised
    ``Exception`` is not ``CommandError``, raise it.
    """
    #設置環境變量，而後運行這個命令
    #如python  manage.py  runserver,  manage.py就是argv[0],runserver是argv[1]
    #create_parser直接調用OptionParser(prog=prog_name,usage=self.usage(subcommand),version=self.get_version(),option_list=self.option_list)
    #將manage.py 和runserver加入參數列表
    #接下來用parser.parse_args進行解析，argv[2]以後爲默認參數，ip地址還有端口號，咱們也能夠顯示的傳進去，默認是127.0.0.1，端口號8000.
    #下面又到了handle_default_options函數。
    #接下來是執行execute函數，還有異常捕獲。
    parser = self.create_parser(argv[0], argv[1])
    options, args = parser.parse_args(argv[2:])
    handle_default_options(options)
    try:
        self.execute(*args, **options.__dict__)
    except Exception as e:
        if options.traceback or not isinstance(e, CommandError):
            raise

        # self.stderr is not guaranteed to be set here
        stderr = getattr(self, 'stderr', OutputWrapper(sys.stderr, self.style.ERROR))
        stderr.write('%s: %s' % (e.__class__.__name__, e))
        sys.exit(1)

下面進入execute函數，前邊是一些設置和錯誤檢查，最主要的是 output = self.handle(*args, **options），能夠發現handle在BaseCommand裏是空的，每一個命令對其進行了重寫。
runserver也是。看看runserver的handle：

def handle(self, addrport='', *args, **options):
    #導入設置模塊
    from django.conf import settings
    #DEBUG和ALLOWED_HOSTS的設置
    if not settings.DEBUG and not settings.ALLOWED_HOSTS:
        raise CommandError('You must set settings.ALLOWED_HOSTS if DEBUG is False.')
    #ipv6的設置
    self.use_ipv6 = options.get('use_ipv6')
    if self.use_ipv6 and not socket.has_ipv6:
        raise CommandError('Your Python does not support IPv6.')
    if args:
        raise CommandError('Usage is runserver %s' % self.args)
    self._raw_ipv6 = False
    if not addrport:
        self.addr = ''
        self.port = DEFAULT_PORT
    else:
        #若是設置了ip地址和端口號，用正則匹配出來
        m = re.match(naiveip_re, addrport)
        if m is None:
            raise CommandError('"%s" is not a valid port number '
                               'or address:port pair.' % addrport)
        self.addr, _ipv4, _ipv6, _fqdn, self.port = m.groups()
        if not self.port.isdigit():
            raise CommandError("%r is not a valid port number." % self.port)
        if self.addr:
            if _ipv6:
                self.addr = self.addr[1:-1]
                self.use_ipv6 = True
                self._raw_ipv6 = True
            elif self.use_ipv6 and not _fqdn:
                raise CommandError('"%s" is not a valid IPv6 address.' % self.addr)
    if not self.addr:
        #若是沒有設置ip地址使用127.0.0.1代替
        self.addr = '::1' if self.use_ipv6 else '127.0.0.1'
        self._raw_ipv6 = bool(self.use_ipv6)
     #運行命令
    self.run(*args, **options)

runserver裏的run方法主要時調用了inner_run(*args, **options）這個方法。

def inner_run(self, *args, **options):
     #省略了部分代碼
        #很熟悉吧，這就是咱們開始運行時，終端上輸出的信息啊。   
        self.stdout.write((
            "%(started_at)s\n"
            "Django version %(version)s, using settings %(settings)r\n"
            "Starting development server at http://%(addr)s:%(port)s/\n"
            "Quit the server with %(quit_command)s.\n"
        ) % {
            "started_at": now,
            "version": self.get_version(),
            "settings": settings.SETTINGS_MODULE,
            "addr": '[%s]' % self.addr if self._raw_ipv6 else self.addr,
            "port": self.port,
            "quit_command": quit_command,
        })
        #加載編碼設置
        translation.activate(settings.LANGUAGE_CODE)

        try:
            handler = self.get_handler(*args, **options)
            run(self.addr, int(self.port), handler,
                ipv6=self.use_ipv6, threading=threading)

          #省略部分代碼



    def get_handler(self, *args, **options):
        """
        Returns the default WSGI handler for the runner.
        """
        return get_internal_wsgi_application()

get_internal__wsgi_application()和run(self.addr, int(self.port), handler,ipv6=self.use_ipv6, threading=threading)都在django.core.servers.basehttp中：

def get_internal_wsgi_application():

    from django.conf import settings
    #在settings模塊中並無找到WSGI_APPLICATION這個環境變量，所以app_path位空
    app_path = getattr(settings, 'WSGI_APPLICATION')
    if app_path is None:
        return get_wsgi_application()

在django/core下wsig.py中的文件以下：就幾句話

import django
from django.core.handlers.wsgi import WSGIHandler


def get_wsgi_application():

    #setup是加載log和settings.INSTALLED_APPS
    django.setup()
    #返回WSGIHhadler類的一個實例
    return WSGIHandler()


class WSGIHandler(base.BaseHandler):
    #初始化一個線程鎖
    initLock = Lock()
    #WSGIRequest爲http.HttpRequest的一個子類，
    #WSGIRequest實現了wsgi規範 
    request_class = WSGIRequest

下面進入run方法：run(self.addr, int(self.port), handler,ipv6=self.use_ipv6, threading=threading)，標準的wsgi實現：

def run(addr, port, wsgi_handler, ipv6=False, threading=False):
    server_address = (addr, port)
    if threading:
        httpd_cls = type(str('WSGIServer'), (socketserver.ThreadingMixIn, WSGIServer), {}) 
    else:
        httpd_cls = WSGIServer
    httpd = httpd_cls(server_address, WSGIRequestHandler, ipv6=ipv6)
    httpd.set_app(wsgi_handler)
    httpd.serve_forever()

httpd_cls(server_address, WSGIRequestHandler, ipv6=ipv6)爲實例化一個WSGIServer類，最終的實例化方法在父類SocketServer中的TCPServer和BaseServer中。包括初始化線程，初始化網絡句柄，像下面的__is_shut_down和__shutdown_request都是在其中初始化的

#處理一個http請求直到關閉
   def serve_forever(self, poll_interval=0.5):
        #__is_shut_down爲一個初始化的threading.Event()的句柄，用於線程間通訊
        #.clear()將標識設置爲false
        self.__is_shut_down.clear()
        try:
            while not self.__shutdown_request:
                #下面的函數就是一個封裝好了的select函數，後面的四個爲傳遞給select函數的參數，分別表示輸入對象列表，輸出對象列表，錯誤對象列表以及超時時間。
                #返回值爲三個列表，表明可寫，可讀，錯誤的事件的對象列表。
                r, w, e = _eintr_retry(select.select, [self], [], [], 
                                       poll_interval)
                #判斷self事件是否在可讀對象列表中，在就進入進行處理
                if self in r:
                    #處理鏈接請求
                    self._handle_request_noblock()
        finally:
            self.__shutdown_request = False
            #將標識設置爲true
            self.__is_shut_down.set()

   #對select函數的封裝        
   def _eintr_retry(func, *args):
    """restart a system call interrupted by EINTR"""
      while True:
        try:
            return func(*args)
        except (OSError, select.error) as e:
            if e.args[0] != errno.EINTR:
                raise


    def _handle_request_noblock(self):

        try:
            #返回請求句柄，客戶端地址，get_request()中調用了self.socket.accept()來實現客戶端的鏈接
            request, client_address = self.get_request()
        except socket.error:
            return
        if self.verify_request(request, client_address):
            try:
                #真正的處理鏈接請求的地方，調用了self.finish_request(request, client_address)
                self.process_request(request, client_address)
            except:
                self.handle_error(request, client_address)
                self.shutdown_request(request)


   def finish_request(self, request, client_address):
        """Finish one request by instantiating RequestHandlerClass."""
        此處的RequestHandlerClass爲初始化的時候傳進來的WSGIRequestHandler，實現了回調。
        self.RequestHandlerClass(request, client_address, self)

在WSGIRequestHandler中實現下面的初始化函數：

def __init__(self, *args, **kwargs):
    from django.conf import settings
    self.admin_static_prefix = urljoin(settings.STATIC_URL, 'admin/')
    # We set self.path to avoid crashes in log_message() on unsupported
    # requests (like "OPTIONS").
    self.path = ''
    self.style = color_style()
    #調用父類的WSGIRequestHandler進行初始化，它的父類是simple_server.py裏的WSGIRequestHandler,它裏面沒有__init__,繼續找它的父類
    #如此重複，在最終的基類中能夠找到__init__方法，位於SocketServer.py中的 BaseRequestHandler類。
    super(WSGIRequestHandler, self).__init__(*args, **kwargs)


    def __init__(self, request, client_address, server):
        self.request = request
        self.client_address = client_address
        self.server = server
        #setup函數
        self.setup()
        try:
            self.handle()
        finally:
            self.finish()

        def setup(self):
            pass

        def handle(self):
            pass

        def finish(self):
            pass

能夠看到裏面的方法並無實現，只是給出了定義，實現都在子類中。

再回到WSGIRequestHandler類中，在simple_server.py中實現了handle函數，實現對請求的處理

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
        #傳入的參數，讀，寫，錯誤，環境變量。在其父類SimpleHandler中進行了初始化，而且打開了多線程和多進程選項
        handler = ServerHandler(
            self.rfile, self.wfile, self.get_stderr(), self.get_environ()
        )
        handler.request_handler = self      # backpointer for logging
        在SimpleHandler的父類BaseHandler中含實現了run方法。此處get_app()是上面的run方法中咱們傳進去的wsgi_handler,httpd.set_app(wsgi_handler)
        handler.run(self.server.get_app())      


    def run(self, application):

        try:
            #設置環境變量
            self.setup_environ()
            #執行WSGIHandler(self.environ,self.start_response)
            #由於類中實現了__call__方法，調用類的實例就至關於調用了__call__方法
            self.result = application(self.environ, self.start_response)
            self.finish_response()
        except:
            try:
                self.handle_error()
            except:
                # If we get an error handling an error, just give up already!
                self.close()
                raise   # ...and let the actual server figure it out.




 def __call__(self, environ, start_response):
    # Set up middleware if needed. We couldn't do this earlier, because
    # settings weren't available.
    if self._request_middleware is None:
        with self.initLock:
            try:
                # Check that middleware is still uninitialised.
                if self._request_middleware is None:
                #嘗試加載中間件
                    self.load_middleware()
            except:
                # Unload whatever middleware we got
                self._request_middleware = None
                raise
    #設置腳本路徑
    set_script_prefix(base.get_script_name(environ))
    signals.request_started.send(sender=self.__class__)
    try:
        request = self.request_class(environ)
    except UnicodeDecodeError:
        logger.warning('Bad Request (UnicodeDecodeError)',
            exc_info=sys.exc_info(),
            extra={
                'status_code': 400,
            }
        )
        response = http.HttpResponseBadRequest()
    else:
        response = self.get_response(request)

    response._handler_class = self.__class__

    status = '%s %s' % (response.status_code, response.reason_phrase)
    response_headers = [(str(k), str(v)) for k, v in response.items()]
    for c in response.cookies.values():
        response_headers.append((str('Set-Cookie'), str(c.output(header=''))))
    start_response(force_str(status), response_headers)
    return response

以上爲我閱讀django源碼的一些心得，大致瞭解了django的一點原理