Django搭建及源码分析(二)
上节针对linux最小系统，如何安装Django，以及配置简单的Django环境进行了说明。
本节从由Django生成的manage.py开始，分析Django源码。python版本2.6，Django版本1.6.11。
manage.py代码很简单。
#!/usr/bin/env python import os import sys if __name__ == "__main__": os.environ.setdefault("DJANGO_SETTINGS_MODULE", "MyDjProj.settings") from django.core.management import execute_from_command_line 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为一个类，传进去的参数列表会进入一个简单的初始化。
class ManagementUtility(object): """ Encapsulates the logic of the django-admin.py and manage.py utilities. A ManagementUtility has a number of commands, which can be manipulated by editing the self.commands dictionary. """ 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。
def execute(self): """ Given the command-line arguments, this figures out which subcommand is being run, creates a parser appropriate to that command, and runs it. """ # Preprocess options to extract --settings and --pythonpath. # These options could affect the commands that are available, so they # must be processed early. 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，LaxOptionParser这个类继承自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。
执行handle_default_options在django.core.management.base中（management/__init__.py前有导入，from django.core.management.base import BaseCommand, CommandError, handle_default_options）
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python path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，执行load_command_class
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。
以runserver命令为例，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。
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. """ """ 以下为上该函数中文说明： #设置环境变量，然后运行这个命令 #如pythonmanage.pyrunserver,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)
执行self.execute，该类的execute方法。
def execute(self, *args, **options): """ Try to execute this command, performing model validation if needed (as controlled by the attribute ``self.requires_model_validation``, except if force-skipped). """ self.stdout = OutputWrapper(options.get('stdout', sys.stdout)) self.stderr = OutputWrapper(options.get('stderr', sys.stderr), self.style.ERROR) if self.can_import_settings: from django.conf import settings saved_locale = None if not self.leave_locale_alone: # Only mess with locales if we can assume we have a working # settings file, because django.utils.translation requires settings # (The final saying about whether the i18n machinery is active will be # found in the value of the USE_I18N setting) if not self.can_import_settings: raise CommandError("Incompatible values of 'leave_locale_alone' " "(%s) and 'can_import_settings' (%s) command " "options." % (self.leave_locale_alone, self.can_import_settings)) # Switch to US English, because django-admin.py creates database # content like permissions, and those shouldn't contain any # translations. from django.utils import translation saved_locale = translation.get_language() translation.activate('en-us') try: if self.requires_model_validation and not options.get('skip_validation'): self.validate() output = self.handle(*args, **options) if output: if self.output_transaction: # This needs to be imported here, because it relies on # settings. from django.db import connections, DEFAULT_DB_ALIAS connection = connections[options.get('database', DEFAULT_DB_ALIAS)] if connection.ops.start_transaction_sql(): self.stdout.write(self.style.SQL_KEYWORD(connection.ops.start_transaction_sql())) self.stdout.write(output) if self.output_transaction: self.stdout.write('\n' + self.style.SQL_KEYWORD("COMMIT;")) finally: if saved_locale is not None: translation.activate(saved_locale)
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): from django.conf import settings if not settings.DEBUG and not settings.ALLOWED_HOSTS: raise CommandError('You must set settings.ALLOWED_HOSTS if DEBUG is False.') 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，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 run(self, *args, **options): """ Runs the server, using the autoreloader if needed """ use_reloader = options.get('use_reloader') if use_reloader: autoreload.main(self.inner_run, args, options) else: self.inner_run(*args, **options) def inner_run(self, *args, **options): from django.conf import settings from django.utils import translation threading = options.get('use_threading') shutdown_message = options.get('shutdown_message', '') quit_command = 'CTRL-BREAK' if sys.platform == 'win32' else 'CONTROL-C' self.stdout.write("Validating models...\n\n") self.validate(display_num_errors=True) now = datetime.now().strftime('%B %d, %Y - %X') if six.PY2: now = now.decode(get_system_encoding())
#这里是开始运行时，打印到终端的信息 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, }) # django.core.management.base forces the locale to en-us. We should # set it up correctly for the first request (particularly important # in the "--noreload" case). 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) except socket.error as e: # Use helpful error messages instead of ugly tracebacks. ERRORS = { errno.EACCES: "You don't have permission to access that port.", errno.EADDRINUSE: "That port is already in use.", errno.EADDRNOTAVAIL: "That IP address can't be assigned-to.", } try: error_text = ERRORS[e.errno] except KeyError: error_text = str(e) self.stderr.write("Error: %s" % error_text) # Need to use an OS exit because sys.exit doesn't work in a thread os._exit(1) except KeyboardInterrupt: if shutdown_message: self.stdout.write(shutdown_message) sys.exit(0)
关键是：handler = self.get_handler(*args, **options)和run(self.addr, int(self.port), handler,
get_handle是self.所以是该类的方法。run不是本类中定义的方法，而由runserver.py开头定义from django.core.servers.basehttp import run, get_internal_wsgi_application
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(): """ Loads and returns the WSGI application as configured by the user in ``settings.WSGI_APPLICATION``. With the default ``startproject`` layout, this will be the ``application`` object in ``projectname/wsgi.py``. This function, and the ``WSGI_APPLICATION`` setting itself, are only useful for Django's internal servers (runserver, runfcgi); external WSGI servers should just be configured to point to the correct application object directly. If settings.WSGI_APPLICATION is not set (is ``None``), we just return whatever ``django.core.wsgi.get_wsgi_application`` returns. """ from django.conf import settings app_path = getattr(settings, 'WSGI_APPLICATION') if app_path is None: return get_wsgi_application() return import_by_path( app_path, error_prefix="WSGI application '%s' could not be loaded; " % app_path )
在settings模块中并没有找到WSGI_APPLICATION这个环境变量，因此app_path为空，执行get_wsgi_application，在django/core下wsig.py中。def get_wsgi_application(): """ The public interface to Django's WSGI support. Should return a WSGI callable. Allows us to avoid making django.core.handlers.WSGIHandler public API, in case the internal WSGI implementation changes or moves in the future. """ return WSGIHandler()
返回一个WSGIHandler实例。
class WSGIHandler(base.BaseHandler):
initLock = Lock()
request_class = WSGIRequest #WSGIRequest实现了wsgi规范
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都是在其中初始化的。
SocketServer.py中的BaseServer中serve_forever()的定义。
def serve_forever(self, poll_interval=0.5): """Handle one request at a time until shutdown. Polls for shutdown every poll_interval seconds. Ignores self.timeout. If you need to do periodic tasks, do them in another thread. """ self.__serving = True #__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() while self.__serving: # XXX: Consider using another file descriptor or # connecting to the socket to wake this up instead of # polling. Polling reduces our responsiveness to a # shutdown request and wastes cpu at all other times. #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 = 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 r: #处理连接请求 self._handle_request_noblock() self.__is_shut_down.set()
调用本类中的_handle_request_noblock()
def _handle_request_noblock(self): """Handle one request, without blocking. I assume that select.select has returned that the socket is readable before this function was called, so there should be no risk of blocking in get_request(). """ 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 self.process_request(request, client_address) except: self.handle_error(request, client_address) self.close_request(request)
在self.process_request中执行了self.finish_request(request, client_address)和self.close_request(request)。
def finish_request(self, request, client_address): """Finish one request by instantiating RequestHandlerClass.""" self.RequestHandlerClass(request, client_address, self)
此处的RequestHandlerClass为初始化的时候传进来的WSGIRequestHandler类，实现了回调。回到httpd = httpd_cls(server_address, WSGIRequestHandler, ipv6=ipv6)，看WSGIRequestHandler类的__init__函数。
class WSGIRequestHandler(simple_server.WSGIRequestHandler, object): 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() super(WSGIRequestHandler, self).__init__(*args, **kwargs)
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。
class BaseRequestHandler: def __init__(self, request, client_address, server): self.request = request self.client_address = client_address self.server = server try: self.setup() self.handle() self.finish() finally: sys.exc_traceback = None # Help garbage collection 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，实现都在继承该类的子类中。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())
handlers.py中BaseHandler中run的定义。
def run(self, application): """Invoke the application""" # Note to self: don't move the close()! Asynchronous servers shouldn't # call close() from finish_response(), so if you close() anywhere but # the double-error branch here, you'll break asynchronous servers by # prematurely closing. Async servers must return from 'run()' without # closing if there might still be output to iterate over. 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.
执行WSGIHandler类的__call__方法。
class WSGIHandler(base.BaseHandler): initLock = Lock() request_class = WSGIRequest 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: #尝试加载中间件 try: # Check that middleware is still uninitialised. if self._request_middleware is None: self.load_middleware() except: # Unload whatever middleware we got self._request_middleware = None raise 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