Horizon 源码阅读（二）—— Horizon 模块注册机制

@property
def _lazy_urls(self):
"""
延迟加载URL模式。
这种方法避免试图加载URLconf值之前设置模块已经加载的问题。
"""
def url_patterns():
return self._urls()[0]
# LazyURLPattern(url_patterns) 猜测这是一个懒惰方法，load的时候把方法传入，当需要使用的使用才执行方法。
# request 请求进来的时候，回去Openstack.urls.py 进行配置，include('openstack_auth.urls')这个时候会执行url_patterns()
# self.namespace = "horizon"
# self.slug = "horizon"
return LazyURLPattern(url_patterns), self.namespace, self.slug

urlpatterns = patterns(
'',
# 匹配网站根目录的URL，映射到openstack_dashboard.views.splash视图。
url(r'^$', 'openstack_dashboard.views.splash', name='splash'),
# 任何以/auth/开头的URL将会匹配,引入openstack_auth.urls
url(r'^auth/', include('openstack_auth.urls')),
# 任何以/api/开头的URL将会匹配,引入openstack_dashboard.api.rest.urls
url(r'^api/', include('openstack_dashboard.api.rest.urls')),
# 任何访问URL将会匹配,都引用horizon.urls
url(r'', include(horizon.urls)),
)

def _urls(self):
"""
从注册的Dashboards构造Horizon的Urlconf
"""
# 获取horizon.site_urls urlpatterns 值
urlpatterns = self._get_default_urlpatterns()
# 从“settings.INSTALLED_APPS发现模块，包含dashboard.py、panel.py的模块注册，添加到注册表中self._registry，没有的抛出异常。
self._autodiscover()-－－－－－－－－－－－－－－－－－－－标注（1）
# 发现每个Dashboards里的Panels
# 从注册表self._registry 取出注册dashboard，注册每个dashboard中的panel
# self._registry:{: ,
# : ,
# : , # : } #self._registry.values():[ , , , ] for dash in self._registry.values(): dash._autodiscover() －－－－－－－－－－－－－－－－－标注（2） # 加载基于插件的面板配置 self._load_panel_customization() # 允许覆盖模块 if self._conf.get("customization_module", None): customization_module = self._conf["customization_module"] bits = customization_module.split('.') mod_name = bits.pop() package = '.'.join(bits) mod = import_module(package) try: before_import_registry = copy.copy(self._registry) import_module('%s.%s' % (package, mod_name)) except Exception: self._registry = before_import_registry if module_has_submodule(mod, mod_name): raise # 编译动态URL配置。 for dash in self._registry.values(): urlpatterns += patterns('', url(r'^%s/' % dash.slug, include(dash._decorated_urls))) # 返回三个参数，django.conf.urls.include “"" 返回的urlpattern参数值 ([ , \S+?)/$>, , (None:None) ^i18n/>, (settings:settings) ^settings/>, (identity:identity) ^identity/>, (project:project) ^project/>, (admin:admin) ^admin/>, (settings:settings) ^settings/>, (identity:identity) ^identity/>, (project:project) ^project/>, (admin:admin) ^admin/>], 'horizon', 'horizon') """ return urlpatterns, self.namespace, self.slug 

def _autodiscover(self):
"""
从“settings.INSTALLED_APPS发现模块注册的
确保适当的模块引入并注册到horizon中
self = """
# 判断self对象中是否存在_registerable_class 如果没有抛出异常，
# 你必须设置一个“registerable_class”属性以使用自动发现。
# self._registerable_class = 这在Class Site中已经设定了。
if not getattr(self, '_registerable_class', None):
raise ImproperlyConfigured('You must set a '
'"_registerable_class" property '
'in order to use autodiscovery.')
'''
循化settings.INSTALLED_APPS，导入每个APP中的dashboard、panel模块，即每个模块下面的dashboard.py 和 panel.py
settings.INSTALLED_APPS => ['openstack_dashboard.dashboards.project',
'openstack_dashboard.dashboards.admin',
'openstack_dashboard.dashboards.identity',
'openstack_dashboard.dashboards.settings',
'openstack_dashboard',
'django.contrib.contenttypes',
'django.contrib.auth',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'django.contrib.humanize',
'django_pyscss',
'openstack_dashboard.django_pyscss_fix',
'compressor',
'horizon',
'openstack_auth']
'''
for mod_name in ('dashboard', 'panel'):
for app in settings.INSTALLED_APPS:
mod = import_module(app)
try:
'''
注册表 self._registry ＝ ｛｝
定义：class Registry(object):
def __init__(self):
self._registry = {}
......
copy.copy():copy.copy 浅拷贝 只拷贝父对象，不会拷贝对象的内部的子对象。
'''
before_import_registry = copy.copy(self._registry)
"""
import_module() 执行这个模块
例如：app：'openstack_dashboard.dashboards.project'
mod_name:'dashboard'
import_module('%s.%s' % (app, mod_name)) =>  执行openstack_dashboard.dashboards.project.dashboard.py => horizon.register(Project)
"""
import_module('%s.%s' % (app, mod_name))
except Exception:
# 如果APP中没有dashboard抛出异常
self._registry = before_import_registry
if module_has_submodule(mod, mod_name):
raise

def _autodiscover(self):
"""      
从当前的dashboard模块中发现panel并注册
"""
# self._autodiscover_complete:True 自动完成发现否时完成的一个标记
if getattr(self, "_autodiscover_complete", False):
return
# self._autodiscover_complete:False
panels_to_discover = []
panel_groups = []
# all(iterable):如果iterable的所有元素不为0、''、False或者iterable为空，all(iterable)返回True，否则返回False；
# basestring:basestring是str和unicode的超类（父类），也是抽象类，因此不能被调用和实例化，
# 但可以被用来判断一个对象是否为str或者unicode的实例，isinstance(obj, basestring)等价于isinstance(obj, (str, unicode))；
# isinstance: 判断一个对象是否是一个已知的类型
#
#例如： self：#      self.panels:('domains', 'projects', 'users', 'groups', 'roles')
if all([isinstance(i, basestring) for i in self.panels]):
self.panels = [self.panels]
# 现在迭代设置panel
# self.panels: [('domains', 'projects', 'users', 'groups', 'roles')]
for panel_set in self.panels:
# 实例化PanelGroup类。
# panel_set:('domains', 'projects', 'users', 'groups', 'roles')
if not isinstance(panel_set, collections.Iterable) and \
issubclass(panel_set, PanelGroup):# 返回错误，panel_set不是一个class  TypeError('issubclass() arg 1 must be a class',)
panel_group = panel_set(self)
# 检查嵌套的元组,并将其转换成PanelGroups
elif not isinstance(panel_set, PanelGroup):
# 返回一个对象
panel_group = PanelGroup(self, panels=panel_set)
# 存放返回结果
# 例如：panel_group.panels:['domains', 'projects', 'users', 'groups', 'roles']
panels_to_discover.extend(panel_group.panels)
panel_groups.append((panel_group.slug, panel_group))
# self._panel_groups:{'default': }
self._panel_groups = SortedDict(panel_groups)
# 加载panel_groups中的每一个panel
# package:'openstack_dashboard.dashboards.settings'
package = '.'.join(self.__module__.split('.')[:-1])
mod = import_module(package)
for panel in panels_to_discover:
try:
before_import_registry = copy.copy(self._registry)
import_module('.%s.panel' % panel, package)
except Exception:
self._registry = before_import_registry
if module_has_submodule(mod, panel):
raise
# 标记自动注册Panel已经完成
self._autodiscover_complete = True