django源码阅读

2

最近再看django-bootstrap-toolkit,一直困惑于静态文件的路径问题。所以只能从源码入手了。
从manage.py开始。
manage.py 比较简单就几句话。

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


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

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

首先看os.environ.setdefault(),environ为类_Environ的一个实例,它继承自IterableUserDict,而IterableUserDict继承自UserDict,包括setdefault()这个方法也是UserDict的一个方法,看一下setdefault实现的功能:

  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,这里的self是一个字典,判断key是不是在里面,不在里面就做一个键值绑定。然后返回。

下面进入execute_from_command_line(sys.argv),sys.argv位一个参数执行的列表,像我们执行python manage.py runserver时,manage.py位sys.argv[0],runserver为sys.argv[1],以此类推,如果有更多参数加的话。

进入django的core模块下,找到management模块。在__init__.py下可以找到该函数

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

我们输入的参数便传到了这个函数里,其中ManagementUtility位一个类穿进去的参数列表会进入一个简单的初始化

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

将参数列表赋给argv,然后返回sys.argv[0]的文件名字给prog_name。
实例化完了之后,再看utility.execute()即类ManagementUtility的execute()方法。

        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)

第一个语句为词法分析,可是找遍了LaxOptionParser这个类也没有找到入口,里面并没有init,只有几个函数,可是python也没有正式的构造函数重载的什么的,后来发现此类继承自OptionParser这个类,它来自于optparse模块,在OptionParser模块里有一个init()函数,会接受若干个参数,进行初始化,这里只是传递了3个参数,usage传递了一个字符串,version为版本,BaseCommand.option_list为一个关于命令行的元组,其中调用了make_option这个类init进行一些初始化,主要初始化_short_opts和_long_opts这两个参数,并且进行了一些检查。_short_opts为短命令,_long_opts为长命令,如-h,--help分别为短命令和长命令。
parser为LaxOptionParser的一个实例。 parser.parse_args(self.argv)这个函数会根据上面初始化的内容进行解析命令行参数,之后返回两个值:options,它是一个对象(,保存有命令行参数值。只要知道命令行参数名,如 file,就可以访问其对应的值: options.file 。args,它是一个由 positional arguments 组成的列表。

    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将解析出来的options对象当做参数,判断settings和pythonpath是否存在,然后
设置环境变量和python模块的搜索路径。

接下来是获得命令行的命令参数self.argv[1],并判断这个命令,包括错误处理,是否时help,是否是version,根据不同的情况展示不同的信息。

最重要的是最后一句,即前面的情况都不是,就进入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

获得django/core/management/commands目录下与INSTALLED_APPS/management/commands目录下的子命令对应的模块前缀

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类的实例。进入management/commands下进入每个文件会发现,每个都有Command类对应相应的命令。

self.fetch_command(subcommand).run_from_argv(self.argv)找到我们输入的命令参数,并且使用run_from_argv执行。

进入runserver这个命令下看一下,Command这个类继承了BaseCommand这个类,BaseCommand在Base.py中,里面有run_from_arv这个方法,在其他的命令里
有的重写了这个方法,不过runserver没有。

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.
    """
    #设置环境变量,然后运行这个命令
    #如python  manage.py  runserver,  manage.py就是argv[0],runserver是argv[1]
    #create_parser直接调用OptionParser(prog=prog_name,usage=self.usage(subcommand),version=self.get_version(),option_list=self.option_list)
    #将manage.py 和runserver加入参数列表
    #接下来用parser.parse_args进行解析,argv[2]之后为默认参数,ip地址还有端口号,我们也可以显示的传进去,默认是127.0.0.1,端口号8000.
    #下面又到了handle_default_options函数。
    #接下来是执行execute函数,还有异常捕获。
    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)

下面进入execute函数,前边是一些设置和错误检查,最主要的是 output = self.handle(*args, **options),可以发现handle在BaseCommand里是空的,每个命令对其进行了重写。
runserver也是。看看runserver的handle:

def handle(self, addrport='', *args, **options):
    #导入设置模块
    from django.conf import settings
    #DEBUG和ALLOWED_HOSTS的设置
    if not settings.DEBUG and not settings.ALLOWED_HOSTS:
        raise CommandError('You must set settings.ALLOWED_HOSTS if DEBUG is False.')
    #ipv6的设置
    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:
        #如果设置了ip地址和端口号,用正则匹配出来
        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:
        #如果没有设置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)
     #运行命令
    self.run(*args, **options)

runserver里的run方法主要时调用了inner_run(*args, **options)这个方法。

   def inner_run(self, *args, **options):
     #省略了部分代码
        #很熟悉吧,这就是我们开始运行时,终端上输出的信息啊。   
        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,
        })
        #加载编码设置
        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)

          #省略部分代码



    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模块中并没有找到WSGI_APPLICATION这个环境变量,因此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中的文件如下:就几句话

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


def get_wsgi_application():

    #setup是加载log和settings.INSTALLED_APPS
    django.setup()
    #返回WSGIHhadler类的一个实例
    return WSGIHandler()


class WSGIHandler(base.BaseHandler):
    #初始化一个线程锁
    initLock = Lock()
    #WSGIRequest为http.HttpRequest的一个子类,
    #WSGIRequest实现了wsgi规范 
    request_class = WSGIRequest

下面进入run方法:run(self.addr, int(self.port), handler,ipv6=self.use_ipv6, threading=threading),标准的wsgi实现:

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)为实例化一个WSGIServer类,最终的实例化方法在父类SocketServer中的TCPServer和BaseServer中。包括初始化线程,初始化网络句柄,像下面的__is_shut_down和__shutdown_request都是在其中初始化的

    #处理一个http请求直到关闭
   def serve_forever(self, poll_interval=0.5):
        #__is_shut_down为一个初始化的threading.Event()的句柄,用于线程间通信
        #.clear()将标识设置为false
        self.__is_shut_down.clear()
        try:
            while not self.__shutdown_request:
                #下面的函数就是一个封装好了的select函数,后面的四个为传递给select函数的参数,分别表示输入对象列表,输出对象列表,错误对象列表以及超时时间。
                #返回值为三个列表,代表可写,可读,错误的事件的对象列表。
                r, w, e = _eintr_retry(select.select, [self], [], [], 
                                       poll_interval)
                #判断self事件是否在可读对象列表中,在就进入进行处理
                if self in r:
                    #处理连接请求
                    self._handle_request_noblock()
        finally:
            self.__shutdown_request = False
            #将标识设置为true
            self.__is_shut_down.set()

   #对select函数的封装        
   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:
            #返回请求句柄,客户端地址,get_request()中调用了self.socket.accept()来实现客户端的连接
            request, client_address = self.get_request()
        except socket.error:
            return
        if self.verify_request(request, client_address):
            try:
                #真正的处理连接请求的地方,调用了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."""
        此处的RequestHandlerClass为初始化的时候传进来的WSGIRequestHandler,实现了回调。
        self.RequestHandlerClass(request, client_address, self)    

在WSGIRequestHandler中实现下面的初始化函数:

 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()
    #调用父类的WSGIRequestHandler进行初始化,它的父类是simple_server.py里的WSGIRequestHandler,它里面没有__init__,继续找它的父类
    #如此重复,在最终的基类中可以找到__init__方法,位于SocketServer.py中的 BaseRequestHandler类。
    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函数
        self.setup()
        try:
            self.handle()
        finally:
            self.finish()

        def setup(self):
            pass

        def handle(self):
            pass

        def finish(self):
            pass

可以看到里面的方法并没有实现,只是给出了定义,实现都在子类中。

再回到WSGIRequestHandler类中,在simple_server.py中实现了handle函数,实现对请求的处理

    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
        #传入的参数,读,写,错误,环境变量。在其父类SimpleHandler中进行了初始化,并且打开了多线程和多进程选项
        handler = ServerHandler(
            self.rfile, self.wfile, self.get_stderr(), self.get_environ()
        )
        handler.request_handler = self      # backpointer for logging
        在SimpleHandler的父类BaseHandler中含实现了run方法。此处get_app()是上面的run方法中我们传进去的wsgi_handler,httpd.set_app(wsgi_handler)
        handler.run(self.server.get_app())      


    def run(self, application):

        try:
            #设置环境变量
            self.setup_environ()
            #执行WSGIHandler(self.environ,self.start_response)
            #因为类中实现了__call__方法,调用类的实例就相当于调用了__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:
                #尝试加载中间件
                    self.load_middleware()
            except:
                # Unload whatever middleware we got
                self._request_middleware = None
                raise
    #设置脚本路径
    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

以上为我阅读django源码的一些心得,大体了解了django的一点原理

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