Django如何启动源码分析

Posted 2021-03-24 zx125

Django如何启动源码分析

启动

我们启动Django是通过python manage.py runsever的命令

解决

这句话就是执行manage.py文件，并在命令行发送一个runsever字符串

解析manage.py

#!/usr/bin/env python
import os
import sys

if __name__ == "__main__":
    #os.environ.setdefault 方法可以修改系统环境变量，但是只能os.environ 只能影响到当前运行程序
    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "zx2.settings")
    try:
        #导入模块，其实这里不单单只是导入execute_from_command_line这个方法，更多的是检查Django的模块，配置是否有问题
        from django.core.management import execute_from_command_line
    except ImportError:
        # The above import may fail for some other reason. Ensure that the
        # issue is really that Django is missing to avoid masking other
        # exceptions on Python 2.
        try:
            #精准判断是不是django模块的问题
            import django
        except ImportError:
            raise ImportError(
                "Couldn't import Django. Are you sure it's installed and "
                "available on your PYTHONPATH environment variable? Did you "
                "forget to activate a virtual environment?"
            )
        raise
    #sys.argv是从外部获取参数，最后执行下面这个方法
    execute_from_command_line(sys.argv)

测试sys.argv

发现两种启动获取的参数不一样，但是第二个参数一样

命令行启动项目
['manage.py', 'runserver']

pycharm 启动项目
['C:/Users/Administrator/Desktop/01python/django/zx1/manage.py', 'runserver', '127.0.0.1:8000']

解析execute_from_command_line(sys.argv)

项目启动入口

def execute_from_command_line(argv=None):
    """
    管理应用程序的简单方法
    A simple method that runs a ManagementUtility.
    """
    utility = ManagementUtility(argv)
    utility.execute()

ManagementUtility初始化代码

class ManagementUtility(object):
    """
    封装django-admin 和 manage.py的公共逻辑代码
    Encapsulates the logic of the django-admin and manage.py utilities.
    """
    def __init__(self, argv=None):
        #把argv给self对象
        self.argv = argv or sys.argv[:]
        #返回path最后的文件名。若path以/或结尾，那么就会返回空值，为zx1
        self.prog_name = os.path.basename(self.argv[0])
        self.settings_exception = None

utility.execute()分析

    def execute(self):
        """
        给定命令行参数，这将确定哪个子命令将要被运行，创建一个适合该命令的解析器，并运行它。
        Given the command-line arguments, this figures out which subcommand is
        being run, creates a parser appropriate to that command, and runs it.
        """
        try:
            #self.argv[1]值为runserver
            subcommand = self.argv[1]
        except IndexError:
            subcommand = 'help'  # Display help if no arguments were given.
        #预处理选项以提取--settings和--pythonpath。
        # Preprocess options to extract --settings and --pythonpath.
        #这些选项可能会影响可用的命令，因此
        # These options could affect the commands that are available, so they
        #必须提前处理。
        # must be processed early.
        #创建一个命令分析器
        parser = CommandParser(None, usage="%(prog)s subcommand [options] [args]", add_help=False)
        parser.add_argument('--settings')
        parser.add_argument('--pythonpath')
        parser.add_argument('args', nargs='*')  # catch-all
        try:
            #self.argv[2:]值为'127.0.0.1:8000'，可以推断出这部分可能和启动服务器有关，并且有默认的ip和端口号
            options, args = parser.parse_known_args(self.argv[2:])
            handle_default_options(options)
        except CommandError:
            pass  # Ignore any option errors at this point.

        try:
        #获取app配置信息
            settings.INSTALLED_APPS
        except ImproperlyConfigured as exc:
            self.settings_exception = exc

        if settings.configured:
            # Start the auto-reloading dev server even if the code is broken.
            # The hardcoded condition is a code smell but we can't rely on a
            # flag on the command class because we haven't located it yet.
            #判断外部输入命令，这部分就是启动的核心代码了
            if subcommand == 'runserver' and '--noreload' not in self.argv:
                try:
                    autoreload.check_errors(django.setup)()
                except Exception:
                    # The exception will be raised later in the child process
                    # started by the autoreloader. Pretend it didn't happen by
                    # loading an empty list of applications.
                    apps.all_models = defaultdict(OrderedDict)
                    apps.app_configs = OrderedDict()
                    apps.apps_ready = apps.models_ready = apps.ready = True

                    # Remove options not compatible with the built-in runserver
                    # (e.g. options for the contrib.staticfiles' runserver).
                    # Changes here require manually testing as described in
                    # #27522.
                    _parser = self.fetch_command('runserver').create_parser('django', 'runserver')
                    _options, _args = _parser.parse_known_args(self.argv[2:])
                    for _arg in _args:
                        self.argv.remove(_arg)

            # In all other cases, django.setup() is required to succeed.
            else:
                django.setup()

        self.autocomplete()

        if subcommand == 'help':
            if '--commands' in args:
                sys.stdout.write(self.main_help_text(commands_only=True) + '
')
            elif len(options.args) < 1:
                sys.stdout.write(self.main_help_text() + '
')
            else:
                self.fetch_command(options.args[0]).print_help(self.prog_name, options.args[0])
        # Special-cases: We want 'django-admin --version' and
        # 'django-admin --help' to work, for backwards compatibility.
        elif subcommand == 'version' or self.argv[1:] == ['--version']:
            sys.stdout.write(django.get_version() + '
')
        elif self.argv[1:] in (['--help'], ['-h']):
            sys.stdout.write(self.main_help_text() + '
')
        else:
            self.fetch_command(subcommand).run_from_argv(self.argv)

后续代码有点看的迷糊了，没有找到socket启动的部分，以后再来