[0-1Django] Core.Management 模块

Core.Management 模块

Management 模块是 Django 的核心模块之一，它承担了 Django 脚手架命令。

通过学习该模块，可以指导自己如何设计脚手架，以及了解脚手架需要哪些功能。

模块结构

.
├── __init__.py
├── base.py                             # 脚手架基类
├── color.py
├── commands                            # 脚手架命令目录 文件名即为命令名
│   ├── __init__.py
│   ├── check.py
│   ├── compilemessages.py
│   ├── createcachetable.py
│   ├── dbshell.py
│   ├── diffsettings.py
│   ├── dumpdata.py
│   ├── flush.py
│   ├── inspectdb.py
│   ├── loaddata.py
│   ├── makemessages.py
│   ├── makemigrations.py
│   ├── migrate.py
│   ├── optimizemigration.py
│   ├── runserver.py
│   ├── sendtestemail.py
│   ├── shell.py
│   ├── showmigrations.py
│   ├── sqlflush.py
│   ├── sqlmigrate.py
│   ├── sqlsequencereset.py
│   ├── squashmigrations.py
│   ├── startapp.py
│   ├── startproject.py
│   ├── test.py
│   └── testserver.py
├── sql.py
├── templates.py                        # 脚手架模板命令，生成项目模板或app模板
└── utils.py

2 directories, 32 files

脚手架执行流程

源码分析

脚手架基类

base.py 文件定义了 BaseCommand 类，该类是所有脚手架命令的基类。

• 子类实现add_arguments方法，可以自定义命令行参数
• 子类实现handle方法，自定义执行命令的主要逻辑

class BaseCommand:

    ...

    def add_arguments(self, parser):
        """
        Entry point for subclassed commands to add custom arguments.
        """
        // 子类实现，自定义命令行参数

    def handle(self, *args, **options):
        """
        The actual logic of the command. Subclasses must implement this method.
        """
        // 子类实现，自定义执行命令的主要逻辑

Command 命令入口run_from_argv

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)
    # 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) # 调用`execute`方法
    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

AppCommand

默认加入了app_label位置参数，允许多个 app_label 传入，并将其传递给handle_app_config方法。

继承此类来快速实现对 app 的命令。

规定了必须实现handle_app_config

def handle_app_config(self, app_config, **options):
    """
    Perform the command's actions for app_config, an AppConfig instance
    corresponding to an application label given on the command line.
    """
    raise NotImplementedError('subclasses of AppCommand must provide a handle_app_config() method')

LabelCommand

默认加入label位置参数，允许多个 label 传入，并将其传递给handle_label方法。

继承此类来快速实现对 label 的命令。

规定了必须实现handle_label

def handle_label(self, label, **options):
    """
    Perform the command's actions for label, a string representing an
    application label given on the command line.
    """
    raise NotImplementedError('subclasses of LabelCommand must provide a handle_label() method')