Django 源码分析（一）：命令分析
Django 源码分析（一）：命令分析
说明：本部分主要介绍 Django 程序在开发中常用的命令是如何控制生成的进行解析；
1. 分析入口
启动命令：
python manage.py runserver 127.0.0.1:8000
项目启动的时候执行的 manage.py 脚本，相关代码如下：
"""Django's command-line utility for administrative tasks."""
import os
import sys
def main():
"""Run administrative tasks."""
# 将配置信息写入环境变量之中;
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'djangoProject1.settings')
try:
# 导入相关的包
from django.core.management import execute_from_command_line
except ImportError as exc:
# 异常的抛出
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?"
) from exc
# 使用 sys.argv 接收参数, 并将信息传递给函数
execute_from_command_line(sys.argv)
if __name__ == '__main__':
main()
上述逻辑将接收到的参数发送给了，传递给了最后的函数进行的处理
def execute_from_command_line(argv=None):
"""Run a ManagementUtility."""
# 将参数传递给类，实例化之后执行 execute() 方法
utility = ManagementUtility(argv)
utility.execute()
2. 参数入口
类的解析
def find_commands(management_dir):
"""
Given a path to a management directory, return a list of all the command
names that are available.
"""
command_dir = os.path.join(management_dir, 'commands')
return [name for _, name, is_pkg in pkgutil.iter_modules([command_dir])
if not is_pkg and not name.startswith('_')]
@functools.lru_cache(maxsize=None)
def get_commands():
"""
Return a dictionary mapping command names to their callback applications.
Look for a management.commands package in django.core, and in each
installed application -- if a commands package exists, register all
commands in that package.
Core commands are always included. If a settings module has been
specified, also include user-defined commands.
The dictionary is in the format {command_name: app_name}. Key-value
pairs from this dictionary can then be used in calls to
load_command_class(app_name, command_name)
If a specific version of a command must be loaded (e.g., with the
startapp command), the instantiated module can be placed in the
dictionary in place of the application name.
The dictionary is cached on the first call and reused on subsequent
calls.
"""
commands = {name: 'django.core' for name in find_commands(__path__[0])}
if not settings.configured: # 检查配置文件, 默认是 True 因此,不会执行下方的 return
return commands
# 进入此处进行循环, 获取每一个 app 中的配置信息;
for app_config in reversed(list(apps.get_app_configs())):
# 使用 os 模块拼接 app 下的 management 下方的 py 文件;
path = os.path.join(app_config.path, 'management')
commands.update({name: app_config.name for name in find_commands(path)})
return commands
class ManagementUtility:
"""
Encapsulate the logic of the django-admin and manage.py utilities.
"""
def __init__(self, argv=None):
self.argv = argv or sys.argv[:]
self.prog_name = os.path.basename(self.argv[0]) # 获取文件的名称 manage.py
if self.prog_name == '__main__.py':
self.prog_name = 'python -m django'
self.settings_exception = None
def main_help_text(self, commands_only=False):
"""Return the script's main help text, as a string."""
if commands_only:
usage = sorted(get_commands())
else:
usage = [
"",
"Type '%s help <subcommand>' for help on a specific subcommand." % self.prog_name,
"",
"Available subcommands:",
]
commands_dict = defaultdict(lambda: [])
for name, app in get_commands().items():
if app == 'django.core':
app = 'django'
else:
app = app.rpartition('.')[-1]
commands_dict[app].append(name)
style = color_style()
for app in sorted(commands_dict):
usage.append("")
usage.append(style.NOTICE("[%s]" % app))
for name in sorted(commands_dict[app]):
usage.append(" %s" % name)
# Output an extra note if settings are not properly configured
if self.settings_exception is not None:
usage.append(style.NOTICE(
"Note that only Django core commands are listed "
"as settings are not properly configured (error: %s)."
% self.settings_exception))
return '\n'.join(usage)
def fetch_command(self, subcommand):
"""
Try to fetch the given subcommand, printing a message with the
appropriate command called from the command line (usually
"django-admin" or "manage.py") if it can't be found.
"""
# Get commands outside of try block to prevent swallowing exceptions
commands = get_commands() # 返回 django.core 的路径,相关代码在该块的顶部
try:
app_name = commands[subcommand] # 执行命令,python manage.py 参数: runserver
except KeyError:
if os.environ.get('DJANGO_SETTINGS_MODULE'): # 获取配置信息
# If `subcommand` is missing due to misconfigured settings, the
# following line will retrigger an ImproperlyConfigured exception
# (get_commands() swallows the original one) so the user is
# informed about it.
settings.INSTALLED_APPS
elif not settings.configured:
sys.stderr.write("No Django settings specified.\n")
possible_matches = get_close_matches(subcommand, commands)
sys.stderr.write('Unknown command: %r' % subcommand)
if possible_matches:
sys.stderr.write('. Did you mean %s?' % possible_matches[0])
sys.stderr.write("\nType '%s help' for usage.\n" % self.prog_name)
sys.exit(1)
# BaseCommand 是 django.core 模块下的一个类
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)
"""
from importlib import import_module # 动态导入模块;
相关函数的代码片段:
def load_command_class(app_name, name):
# 导入相关的命令
module = import_module('%s.management.commands.%s' % (app_name, name))
return module.Command()
"""
return klass
def autocomplete(self):
"""
Output completion suggestions for BASH.
The output of this function is passed to BASH's `COMREPLY` variable and
treated as completion suggestions. `COMREPLY` expects a space
separated string as the result.
The `COMP_WORDS` and `COMP_CWORD` BASH environment variables are used
to get information about the cli input. Please refer to the BASH
man-page for more information about this variables.
Subcommand options are saved as pairs. A pair consists of
the long option string (e.g. '--exclude') and a boolean
value indicating if the option requires arguments. When printing to
stdout, an equal sign is appended to options which require arguments.
Note: If debugging this function, it is recommended to write the debug
output in a separate file. Otherwise the debug output will be treated
and formatted as potential completion suggestions.
"""
# Don't complete if user hasn't sourced bash_completion file.
if 'DJANGO_AUTO_COMPLETE' not in os.environ:
return
cwords = os.environ['COMP_WORDS'].split()[1:]
cword = int(os.environ['COMP_CWORD'])
try:
curr = cwords[cword - 1]
except IndexError:
curr = ''
subcommands = [*get_commands(), 'help']
options = [('--help', False)]
# subcommand
if cword == 1:
print(' '.join(sorted(filter(lambda x: x.startswith(curr), subcommands))))
# subcommand options
# special case: the 'help' subcommand has no options
elif cwords[0] in subcommands and cwords[0] != 'help':
subcommand_cls = self.fetch_command(cwords[0])
# special case: add the names of installed apps to options
if cwords[0] in ('dumpdata', 'sqlmigrate', 'sqlsequencereset', 'test'):
try:
app_configs = apps.get_app_configs()
# Get the last part of the dotted path as the app name.
options.extend((app_config.label, 0) for app_config in app_configs)
except ImportError:
# Fail silently if DJANGO_SETTINGS_MODULE isn't set. The
# user will find out once they execute the command.
pass
parser = subcommand_cls.create_parser('', cwords[0])
options.extend(
(min(s_opt.option_strings), s_opt.nargs != 0)
for s_opt in parser._actions if s_opt.option_strings
)
# filter out previously specified options from available options
prev_opts = {x.split('=')[0] for x in cwords[1:cword - 1]}
options = (opt for opt in options if opt[0] not in prev_opts)
# filter options by current input
options = sorted((k, v) for k, v in options if k.startswith(curr))
for opt_label, require_arg in options:
# append '=' to options which require args
if require_arg:
opt_label += '='
print(opt_label)
# Exit code of the bash completion function is never passed back to
# the user, so it's safe to always exit with 0.
# For more details see #25420.
sys.exit(0)
def execute(self):
"""
Given the command-line arguments, figure out which subcommand is being
run, create a parser appropriate to that command, and run it.
"""
try:
subcommand = self.argv[1] # 获取后面的参数
except IndexError:
subcommand = 'help' # Display help if no arguments were given.
# Preprocess options to extract --settings and --pythonpath.
# These options could affect the commands that are available, so they
# must be processed early.
parser = CommandParser(
prog=self.prog_name,
usage='%(prog)s subcommand [options] [args]',
add_help=False,
allow_abbrev=False,
)
# 添加相关的参数信息
parser.add_argument('--settings')
parser.add_argument('--pythonpath')
parser.add_argument('args', nargs='*') # catch-all
try:
options, args = parser.parse_known_args(self.argv[2:])
handle_default_options(options)
except CommandError:
pass # Ignore any option errors at this point.
try:
settings.INSTALLED_APPS
except ImproperlyConfigured as exc:
self.settings_exception = exc
except ImportError 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.
if subcommand == 'runserver' and '--noreload' not in self.argv:
try:
# 嵌套函数,检查是否出错并且抛出异常, 执行 django.setup
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(dict)
apps.app_configs = {}
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() # 执行该函数，加载app
self.autocomplete()
if subcommand == 'help':
# 终端输出帮助信息
if '--commands' in args:
sys.stdout.write(self.main_help_text(commands_only=True) + '\n')
elif not options.args:
sys.stdout.write(self.main_help_text() + '\n')
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() + '\n') # 输出版本信息
elif self.argv[1:] in (['--help'], ['-h']):
sys.stdout.write(self.main_help_text() + '\n')
else:
# 通过命令查询函数,查询命令,执行命令,run_from_argv 是 BaseCommand 的方法，内部会调用底层的execute 方法
self.fetch_command(subcommand).run_from_argv(self.argv)
ManagementUtility 类中调用的其他类的方法，下方的这个类继承内置的参数处理的模块，点击这里，进行详细阅读；
class CommandParser(ArgumentParser):
"""
Customized ArgumentParser class to improve some error messages and prevent
SystemExit in several occasions, as SystemExit is unacceptable when a
command is called programmatically.
"""
def __init__(self, *, missing_args_message=None, called_from_command_line=None, **kwargs):
""" 多封装两个参数, 并且执行父类的初始化方法; """
self.missing_args_message = missing_args_message
self.called_from_command_line = called_from_command_line
super().__init__(**kwargs)
def parse_args(self, args=None, namespace=None):
# Catch missing argument for a better error message
if (self.missing_args_message and
not (args or any(not arg.startswith('-') for arg in args))):
self.error(self.missing_args_message)
return super().parse_args(args, namespace)
def error(self, message):
if self.called_from_command_line:
super().error(message)
else:
raise CommandError("Error: %s" % message)
执行的 django.setup 函数内容如下
def setup(set_prefix=True):
"""
Configure the settings (this happens as a side effect of accessing the
first setting), configure logging and populate the app registry.
Set the thread-local urlresolvers script prefix if `set_prefix` is True.
"""
from django.apps import apps
from django.conf import settings
from django.urls import set_script_prefix
from django.utils.log import configure_logging
configure_logging(settings.LOGGING_CONFIG, settings.LOGGING)
if set_prefix:
# 设置当前线程脚本的前缀
set_script_prefix(
'/' if settings.FORCE_SCRIPT_NAME is None else settings.FORCE_SCRIPT_NAME
)
"""
from asgiref.local import Local
简单解释：Local 是 threading.locals 的直接替代品，也适用于 asyncio 任务
通过 current_task asyncio 方法，并通过 sync_to_async 和 async_to_sync传递局部变量。
_prefixes = Local()
...
def set_script_prefix(prefix):
if not prefix.endswith('/'):
prefix += '/'
_prefixes.value = prefix
"""
apps.populate(settings.INSTALLED_APPS) # 加载每一个 app 生成 app 的对象;
执行 app 的加载
def populate(self, installed_apps=None):
"""
Load application configurations and models.
Import each application module and then each model module.
It is thread-safe and idempotent, but not reentrant.
"""
if self.ready:
return
# populate() might be called by two threads in parallel on servers
# that create threads before initializing the WSGI callable.
with self._lock:
if self.ready:
return
# An RLock prevents other threads from entering this section. The
# compare and set operation below is atomic.
if self.loading:
# Prevent reentrant calls to avoid running AppConfig.ready()
# methods twice.
raise RuntimeError("populate() isn't reentrant")
self.loading = True
# Phase 1: initialize app configs and import app modules.
for entry in installed_apps:
if isinstance(entry, AppConfig):
app_config = entry
else:
app_config = AppConfig.create(entry)
if app_config.label in self.app_configs:
raise ImproperlyConfigured(
"Application labels aren't unique, "
"duplicates: %s" % app_config.label)
self.app_configs[app_config.label] = app_config
app_config.apps = self
# Check for duplicate app names.
counts = Counter(
app_config.name for app_config in self.app_configs.values())
duplicates = [
name for name, count in counts.most_common() if count > 1]
if duplicates:
raise ImproperlyConfigured(
"Application names aren't unique, "
"duplicates: %s" % ", ".join(duplicates))
self.apps_ready = True
# Phase 2: import models modules.
for app_config in self.app_configs.values():
app_config.import_models()
self.clear_cache()
self.models_ready = True
# Phase 3: run ready() methods of app configs.
for app_config in self.get_app_configs():
app_config.ready()
self.ready = True
self.ready_event.set()
3. 命令对应与执行
上述的过程中最后执行的是
# 通过命令查询函数,查询命令,执行命令,run_from_argv 是 BaseCommand 的方法，内部会调用底层的execute 方法
self.fetch_command(subcommand).run_from_argv(self.argv)
特别注意：这里的self表示的是当前的对象，因此执行不同命令的时候也是不一样的对象；
以下内容基于runserver命令进行的解析，fetch_command 会导入 django.core 模块下的信息，因此对应的命令信息只能在django.core 目录下进行查看；
class BaseCommand:
""" 上述过程调用的 BaseComand 中的方法;"""
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.
"""
self._called_from_command_line = True
parser = self.create_parser(argv[0], argv[1])
options = parser.parse_args(argv[2:])
cmd_options = vars(options) # 返回对象属性值和字典, 备注只返回实例属性的字典
# Move positional args out of options to mimic legacy optparse
args = cmd_options.pop('args', ())
handle_default_options(options)
try:
self.execute(*args, **cmd_options)
except CommandError as e:
if options.traceback:
raise
# SystemCheckError takes care of its own formatting.
if isinstance(e, SystemCheckError):
self.stderr.write(str(e), lambda x: x)
else:
self.stderr.write('%s: %s' % (e.__class__.__name__, e))
sys.exit(e.returncode)
finally:
try:
connections.close_all()
except ImproperlyConfigured:
# Ignore if connections aren't setup at this point (e.g. no
# configured settings).
pass
# 调用执行的execute方法
def execute(self, *args, **options):
"""
Try to execute this command, performing system checks if needed (as
controlled by the ``requires_system_checks`` attribute, except if
force-skipped).
"""
if options['force_color'] and options['no_color']:
raise CommandError("The --no-color and --force-color options can't be used together.")
if options['force_color']:
self.style = color_style(force_color=True) # django 配色方案
elif options['no_color']:
self.style = no_style()
self.stderr.style_func = None
if options.get('stdout'):
self.stdout = OutputWrapper(options['stdout'])
if options.get('stderr'):
self.stderr = OutputWrapper(options['stderr'])
# 进行检查
if self.requires_system_checks and not options['skip_checks']:
if self.requires_system_checks == ALL_CHECKS:
self.check()
else:
self.check(tags=self.requires_system_checks)
# 进行数据库迁移的检查
if self.requires_migrations_checks:
self.check_migrations()
# 执行 handle 方法, 因此 handle 在子类中必须要实现
output = self.handle(*args, **options)
if output:
if self.output_transaction:
connection = connections[options.get('database', DEFAULT_DB_ALIAS)]
output = '%s\n%s\n%s' % (
self.style.SQL_KEYWORD(connection.ops.start_transaction_sql()),
output,
self.style.SQL_KEYWORD(connection.ops.end_transaction_sql()),
)
self.stdout.write(output)
return output
def check(self, app_configs=None, tags=None, display_num_errors=False,
include_deployment_checks=False, fail_level=checks.ERROR,
databases=None):
"""
Use the system check framework to validate entire Django project.
Raise CommandError for any serious message (error or critical errors).
If there are only light messages (like warnings), print them to stderr
and don't raise an exception.
"""
all_issues = checks.run_checks(
app_configs=app_configs,
tags=tags,
include_deployment_checks=include_deployment_checks,
databases=databases,
)
header, body, footer = "", "", ""
visible_issue_count = 0 # excludes silenced warnings
if all_issues:
debugs = [e for e in all_issues if e.level < checks.INFO and not e.is_silenced()]
infos = [e for e in all_issues if checks.INFO <= e.level < checks.WARNING and not e.is_silenced()]
warnings = [e for e in all_issues if checks.WARNING <= e.level < checks.ERROR and not e.is_silenced()]
errors = [e for e in all_issues if checks.ERROR <= e.level < checks.CRITICAL and not e.is_silenced()]
criticals = [e for e in all_issues if checks.CRITICAL <= e.level and not e.is_silenced()]
sorted_issues = [
(criticals, 'CRITICALS'),
(errors, 'ERRORS'),
(warnings, 'WARNINGS'),
(infos, 'INFOS'),
(debugs, 'DEBUGS'),
]
for issues, group_name in sorted_issues:
if issues:
visible_issue_count += len(issues)
formatted = (
self.style.ERROR(str(e))
if e.is_serious()
else self.style.WARNING(str(e))
for e in issues)
formatted = "\n".join(sorted(formatted))
body += '\n%s:\n%s\n' % (group_name, formatted)
if visible_issue_count:
header = "System check identified some issues:\n"
if display_num_errors:
if visible_issue_count:
footer += '\n'
footer += "System check identified %s (%s silenced)." % (
"no issues" if visible_issue_count == 0 else
"1 issue" if visible_issue_count == 1 else
"%s issues" % visible_issue_count,
len(all_issues) - visible_issue_count,
)
if any(e.is_serious(fail_level) and not e.is_silenced() for e in all_issues):
msg = self.style.ERROR("SystemCheckError: %s" % header) + body + footer
raise SystemCheckError(msg)
else:
msg = header + body + footer
if msg:
if visible_issue_count:
self.stderr.write(msg, lambda x: x)
else:
self.stdout.write(msg)
def check_migrations(self):
"""
Print a warning if the set of migrations on disk don't match the
migrations in the database.
"""
from django.db.migrations.executor import MigrationExecutor
try:
executor = MigrationExecutor(connections[DEFAULT_DB_ALIAS])
except ImproperlyConfigured:
# No databases are configured (or the dummy one)
return
plan = executor.migration_plan(executor.loader.graph.leaf_nodes())
if plan:
apps_waiting_migration = sorted({migration.app_label for migration, backwards in plan})
self.stdout.write(
self.style.NOTICE(
"\nYou have %(unapplied_migration_count)s unapplied migration(s). "
"Your project may not work properly until you apply the "
"migrations for app(s): %(apps_waiting_migration)s." % {
"unapplied_migration_count": len(plan),
"apps_waiting_migration": ", ".join(apps_waiting_migration),
}
)
)
self.stdout.write(self.style.NOTICE("Run 'python manage.py migrate' to apply them."))
def handle(self, *args, **options):
"""
The actual logic of the command. Subclasses must implement
this method.
"""
# 抽象方法
raise NotImplementedError('subclasses of BaseCommand must provide a handle() method')
但是动态导入的情况可以是根据不同的情况进行的导入
from importlib import import_module # 动态导入模块;
相关函数的代码片段:
def load_command_class(app_name, name):
# 导入相关的命令
module = import_module('%s.management.commands.%s' % (app_name, name))
return module.Command()
相关的脚本名称，我们分析启动的 runserver.py 文件
import errno
import os
import re
import socket
import sys
from datetime import datetime
from django.conf import settings
from django.core.management.base import BaseCommand, CommandError
from django.core.servers.basehttp import (
WSGIServer, get_internal_wsgi_application, run,
)
from django.utils import autoreload
from django.utils.regex_helper import _lazy_re_compile
naiveip_re = _lazy_re_compile(r"""^(?:
(?P<addr>
(?P<ipv4>\d{1,3}(?:\.\d{1,3}){3}) | # IPv4 address
(?P<ipv6>\[[a-fA-F0-9:]+\]) | # IPv6 address
(?P<fqdn>[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)*) # FQDN
):)?(?P<port>\d+)$""", re.X)
# 继承 BaseCommand
class Command(BaseCommand):
help = "Starts a lightweight Web server for development."
# Validation is called explicitly each time the server is reloaded.
requires_system_checks = []
stealth_options = ('shutdown_message',)
default_addr = '127.0.0.1'
default_addr_ipv6 = '::1'
default_port = '8000'
protocol = 'http'
server_cls = WSGIServer
def add_arguments(self, parser):
parser.add_argument(
'addrport', nargs='?',
help='Optional port number, or ipaddr:port'
)
parser.add_argument(
'--ipv6', '-6', action='store_true', dest='use_ipv6',
help='Tells Django to use an IPv6 address.',
)
parser.add_argument(
'--nothreading', action='store_false', dest='use_threading',
help='Tells Django to NOT use threading.',
)
parser.add_argument(
'--noreload', action='store_false', dest='use_reloader',
help='Tells Django to NOT use the auto-reloader.',
)
# 重写了 execute 方法, 因此会执行当前对象也是此处的,
def execute(self, *args, **options):
if options['no_color']:
# We rely on the environment because it's currently the only
# way to reach WSGIRequestHandler. This seems an acceptable
# compromise considering `runserver` runs indefinitely.
os.environ["DJANGO_COLORS"] = "nocolor"
super().execute(*args, **options) # 执行父类的 execute 放啊
def get_handler(self, *args, **options):
"""Return the default WSGI handler for the runner."""
return get_internal_wsgi_application()
# 实现了 handle 方法
def handle(self, *args, **options):
# 启动函数中会调用实现类中的handle 方法
# 检查 debug 和 允许的地址
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['use_ipv6']
if self.use_ipv6 and not socket.has_ipv6:
raise CommandError('Your Python does not support IPv6.')
self._raw_ipv6 = False
if not options['addrport']:
self.addr = ''
self.port = self.default_port
else:
# 使用正则匹配地址和端口号
m = re.match(naiveip_re, options['addrport'])
if m is None:
raise CommandError('"%s" is not a valid port number '
'or address:port pair.' % options['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:
self.addr = self.default_addr_ipv6 if self.use_ipv6 else self.default_addr
self._raw_ipv6 = self.use_ipv6
self.run(**options) # 调用内置的 run 方法
def run(self, **options):
"""Run the server, using the autoreloader if needed."""
use_reloader = options['use_reloader']
if use_reloader:
# 内部使用 subprocess.run 开启子任务,执行的是 inner_run()
autoreload.run_with_reloader(self.inner_run, **options)
"""
相关代码
def run_with_reloader(main_func, *args, **kwargs):
signal.signal(signal.SIGTERM, lambda *args: sys.exit(0))
try:
if os.environ.get(DJANGO_AUTORELOAD_ENV) == 'true':
reloader = get_reloader()
logger.info('Watching for file changes with %s', reloader.__class__.__name__)
start_django(reloader, main_func, *args, **kwargs)
else:
exit_code = restart_with_reloader()
sys.exit(exit_code)
except KeyboardInterrupt:
pass
def restart_with_reloader():
new_environ = {**os.environ, DJANGO_AUTORELOAD_ENV: 'true'}
args = get_child_arguments()
while True:
p = subprocess.run(args, env=new_environ, close_fds=False)
if p.returncode != 3:
return p.returncode
"""
else:
self.inner_run(None, **options)
def inner_run(self, *args, **options):
# If an exception was silenced in ManagementUtility.execute in order
# to be raised in the child process, raise it now.
autoreload.raise_last_exception() # 存在异常则抛出
threading = options['use_threading']
# 'shutdown_message' is a stealth option.
shutdown_message = options.get('shutdown_message', '') # 获取关闭参数
quit_command = 'CTRL-BREAK' if sys.platform == 'win32' else 'CONTROL-C'
self.stdout.write("Performing system checks...\n\n")
self.check(display_num_errors=True)
# Need to check migrations here, so can't use the
# requires_migrations_check attribute.
self.check_migrations() # 检查数据库的信息
now = datetime.now().strftime('%B %d, %Y - %X')
self.stdout.write(now)
self.stdout.write((
"Django version %(version)s, using settings %(settings)r\n"
"Starting development server at %(protocol)s://%(addr)s:%(port)s/\n"
"Quit the server with %(quit_command)s."
) % {
"version": self.get_version(),
"settings": settings.SETTINGS_MODULE,
"protocol": self.protocol,
"addr": '[%s]' % self.addr if self._raw_ipv6 else self.addr,
"port": self.port,
"quit_command": quit_command,
})
try:
# 返回get_wsgi
handler = self.get_handler(*args, **options)
# 调用run方法
run(self.addr, int(self.port), handler,
ipv6=self.use_ipv6, threading=threading, server_cls=self.server_cls)
except OSError 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 = 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) # 异常退出
调用的 run 方法如下：
class WSGIServer(simple_server.WSGIServer): # 继承了 python 内置的WSGI类; WSGIServer 继承TCPServer
"""BaseHTTPServer that implements the Python WSGI protocol"""
request_queue_size = 10
def __init__(self, *args, ipv6=False, allow_reuse_address=True, **kwargs):
if ipv6:
self.address_family = socket.AF_INET6
self.allow_reuse_address = allow_reuse_address
super().__init__(*args, **kwargs)
def handle_error(self, request, client_address):
if is_broken_pipe_error():
logger.info("- Broken pipe from %s\n", client_address)
else:
super().handle_error(request, client_address)
def run(addr, port, wsgi_handler, ipv6=False, threading=False, server_cls=WSGIServer):
server_address = (addr, port) # 构建请求地址与端口号
if threading:
httpd_cls = type('WSGIServer', (socketserver.ThreadingMixIn, server_cls), {})
else:
httpd_cls = server_cls
httpd = httpd_cls(server_address, WSGIRequestHandler, ipv6=ipv6)
if threading:
# ThreadingMixIn.daemon_threads indicates how threads will behave on an
# abrupt shutdown; like quitting the server by the user or restarting
# by the auto-reloader. True means the server will not wait for thread
# termination before it quits. This will make auto-reloader faster
# and will prevent the need to kill the server manually if a thread
# isn't terminating correctly.
httpd.daemon_threads = True
httpd.set_app(wsgi_handler)
httpd.serve_forever() # 启动监听的服务, 每次会处理一个请求并且当做一个线程;
至此命令分析部分完结，一些其他命令的解析，可以查看commands下的脚本文件进行探索；
4. 总结
通过上述的分析我们可以得出结论：命令的执行主要是执行相对应的脚本文件；
命令首先从 manage.py 开始执行，通过 execute_from_command_line 函数（sys.argv 作为参数），然后调用 ManagementUtility 类进行实例化，该实例调用 execute 方法。
这里主要进行了一些参数的预处理，然后调用 fetch_command(subcommand) 方法，这个先找到所有可用的命令，根据 subcommand 参数获取到一个基类为 BaseCommand 的一个实例，然后这个实例调用 run_from_argv 方法（该方法位于 BaseCommand 中），然后调用 execute 方法，该方法下又调用 handle 方法来实现自己的逻辑。
5. 扩展使用
通过上述的分析，我们可以自定义扩展自己的命令；
# 可扩展部分的源码;
@functools.lru_cache(maxsize=None)
def get_commands():
commands = {name: 'django.core' for name in find_commands(__path__[0])}
if not settings.configured: # 检查配置文件, 默认是 True 因此,不会执行下方的 return
return commands
# 进入此处进行循环, 获取每一个 app 中的配置信息;
for app_config in reversed(list(apps.get_app_configs())):
# 使用 os 模块拼接 app 下的 management 下方的 py 文件;
path = os.path.join(app_config.path, 'management')
# 将拼接的部分进行字典
commands.update({name: app_config.name for name in find_commands(path)})
# 返回命令的字典信息;
return commands
因此扩展命令的时候需要在 app 下创建 management/commands 文件夹（这个是必须的），文件名称你可以随便定义，例如 custom_command.py，那么调用的时候就是 python manage.py custom_command。
在脚本文件中我们需要定义一个类Command, 并继承 BaseCommand（处于 django/core/management/base 下），然后类下实现一个 handle 方法（必须的）（实现你自己的逻辑）
# -*- coding: utf-8 -*-
from django.core.management.base import BaseCommand
class Command(BaseCommand):
""" 继承抽象类, 实现扩展的方法;
"""
def handle(self, *args, **options):
"""
逻辑实现方式;
:param args:
:param options:
:return:
"""
print("开始执行自定义的扩展方法;")
print("django的命令实现了开闭原则, 对修改封闭, 对扩展开放!")
print("自定义的扩展方法执行完成;")
自定义的命令经常用在数据初始化的过程中，例如创建用户，插入原生的数据信息的时候使用；
继续努力，终成大器；
