Zope 3's Local Component Architecture

This package provides a local and persistent site manager implementation, so that one can register local utilities and adapters. It uses local adapter registries for its adapter and utility registry. The module also provides some facilities to organize the local software and ensures the correct behavior inside the ZODB.

Sites and Local Site Managers

This is an introduction of location-based component architecture.

Creating and Accessing Sites

Sites are used to provide custom component setups for parts of your application or web site. Every folder:

>>> from zope.site import folder
>>> myfolder = folder.rootFolder()

has the potential to become a site:

>>> from zope.component.interfaces import ISite, IPossibleSite
>>> IPossibleSite.providedBy(myfolder)

but is not yet one:

>>> ISite.providedBy(myfolder)

If you would like your custom content component to be able to become a site, you can use the SiteManagerContainer mix-in class:

>>> from zope import site
>>> class MyContentComponent(site.SiteManagerContainer):
...     pass
>>> myContent = MyContentComponent()
>>> IPossibleSite.providedBy(myContent)
>>> ISite.providedBy(myContent)

To convert a possible site to a real site, we have to provide a site manager:

>>> sm = site.LocalSiteManager(myfolder)
>>> myfolder.setSiteManager(sm)
>>> ISite.providedBy(myfolder)
>>> myfolder.getSiteManager() is sm

Note that an event is generated when a local site manager is created:

>>> from zope.component.eventtesting import getEvents
>>> from zope.site.interfaces import INewLocalSite
>>> [event] = getEvents(INewLocalSite)
>>> event.manager is sm

If one tries to set a bogus site manager, a ValueError will be raised:

>>> myfolder2 = folder.Folder()
>>> myfolder2.setSiteManager(object)
Traceback (most recent call last):
ValueError: setSiteManager requires an IComponentLookup

If the possible site has been changed to a site already, a TypeError is raised when one attempts to add a new site manager:

>>> myfolder.setSiteManager(site.LocalSiteManager(myfolder))
Traceback (most recent call last):
TypeError: Already a site

There is also an adapter you can use to get the next site manager from any location:

>>> myfolder['mysubfolder'] = folder.Folder()
>>> import zope.component
>>> zope.component.interfaces.IComponentLookup(myfolder['mysubfolder']) is sm

If the location passed is a site, the site manager of that site is returned:

>>> zope.component.interfaces.IComponentLookup(myfolder) is sm

Using the Site Manager

A site manager contains several site management folders, which are used to logically organize the software. When a site manager is initialized, a default site management folder is created:

>>> sm = myfolder.getSiteManager()
>>> default = sm['default']
>>> default.__class__
<class 'zope.site.site.SiteManagementFolder'>

However, you can tell not to create the default site manager folder on LocalSiteManager creation:

>>> nodefault = site.LocalSiteManager(myfolder, default_folder=False)
>>> 'default' in nodefault

Also, note that when creating LocalSiteManager, its __parent__ is set to site that was passed to constructor and the __name__ is set to ++etc++site.

>>> nodefault.__parent__ is myfolder
>>> nodefault.__name__ == '++etc++site'

You can easily create a new site management folder:

>>> sm['mySMF'] = site.SiteManagementFolder()
>>> sm['mySMF'].__class__
<class 'zope.site.site.SiteManagementFolder'>

Once you have your site management folder -- let's use the default one -- we can register some components. Let's start with a utility:

>>> import zope.interface
>>> class IMyUtility(zope.interface.Interface):
...     pass
>>> import persistent
>>> from zope.container.contained import Contained
>>> @zope.interface.implementer(IMyUtility)
... class MyUtility(persistent.Persistent, Contained):
...     def __init__(self, title):
...         self.title = title
...     def __repr__(self):
...         return "%s('%s')" %(self.__class__.__name__, self.title)

Now we can create an instance of our utility and put it in the site management folder and register it:

>>> myutil = MyUtility('My custom utility')
>>> default['myutil'] = myutil
>>> sm.registerUtility(myutil, IMyUtility, 'u1')

Now we can ask the site manager for the utility:

>>> sm.queryUtility(IMyUtility, 'u1')
MyUtility('My custom utility')

Of course, the local site manager has also access to the global component registrations:

>>> gutil = MyUtility('Global Utility')
>>> from zope.component import getGlobalSiteManager
>>> gsm = getGlobalSiteManager()
>>> gsm.registerUtility(gutil, IMyUtility, 'gutil')
>>> sm.queryUtility(IMyUtility, 'gutil')
MyUtility('Global Utility')

Next let's see whether we can also successfully register an adapter as well. Here the adapter will provide the size of a file:

>>> class IFile(zope.interface.Interface):
...     pass
>>> class ISized(zope.interface.Interface):
...     pass
>>> @zope.interface.implementer(IFile)
... class File(object):
...     pass
>>> @zope.interface.implementer(ISized)
... class FileSize(object):
...     def __init__(self, context):
...         self.context = context

Now that we have the adapter we need to register it:

>>> sm.registerAdapter(FileSize, [IFile])

Finally, we can get the adapter for a file:

>>> file = File()
>>> size = sm.queryAdapter(file, ISized, name='')
>>> size.__class__
<class 'FileSize'>
>>> size.context is file

By the way, once you set a site

>>> from zope.component import hooks
>>> hooks.setSite(myfolder)

you can simply use the zope.component's getSiteManager() method to get the nearest site manager:

>>> from zope.component import getSiteManager
>>> getSiteManager() is sm

This also means that you can simply use zope.component to look up your utility

>>> from zope.component import getUtility
>>> getUtility(IMyUtility, 'gutil')
MyUtility('Global Utility')

or the adapter via the interface's __call__ method:

>>> size = ISized(file)
>>> size.__class__
<class 'FileSize'>
>>> size.context is file

Multiple Sites

Until now we have only dealt with one local and the global site. But things really become interesting, once we have multiple sites. We can override other local configuration.

This behaviour uses the notion of location, therefore we need to configure the zope.location package first:

>>> import zope.configuration.xmlconfig
>>> _  = zope.configuration.xmlconfig.string("""
... <configure xmlns="http://namespaces.zope.org/zope">
...   <include package="zope.component" file="meta.zcml"/>
...   <include package="zope.location" />
... </configure>
... """)

Let's now create a new folder called folder11, add it to myfolder and make it a site:

>>> myfolder11 = folder.Folder()
>>> myfolder['myfolder11'] = myfolder11
>>> myfolder11.setSiteManager(site.LocalSiteManager(myfolder11))
>>> sm11 = myfolder11.getSiteManager()

If we ask the second site manager for its next, we get

>>> sm11.__bases__ == (sm, )

and the first site manager should have the folling sub manager:

>>> sm.subs == (sm11,)

If we now register a second utility with the same name and interface with the new site manager folder,

>>> default11 = sm11['default']
>>> myutil11 = MyUtility('Utility, uno & uno')
>>> default11['myutil'] = myutil11
>>> sm11.registerUtility(myutil11, IMyUtility, 'u1')

then it will will be available in the second site manager

>>> sm11.queryUtility(IMyUtility, 'u1')
MyUtility('Utility, uno & uno')

but not in the first one:

>>> sm.queryUtility(IMyUtility, 'u1')
MyUtility('My custom utility')

It is also interesting to look at the use cases of moving and copying a site. To do that we create a second root folder and make it a site, so that site hierarchy is as follows:

         _____ global site _____
        /                       \
    myfolder1                myfolder2

>>> myfolder2 = folder.rootFolder()
>>> myfolder2.setSiteManager(site.LocalSiteManager(myfolder2))

Before we can move or copy sites, we need to register two event subscribers that manage the wiring of site managers after moving or copying:

>>> from zope import container
>>> gsm.registerHandler(
...    site.changeSiteConfigurationAfterMove,
...    (ISite, container.interfaces.IObjectMovedEvent),
...    )

We only have to register one event listener, since the copy action causes an IObjectAddedEvent to be created, which is just a special type of IObjectMovedEvent.

First, make sure that everything is setup correctly in the first place:

>>> myfolder11.getSiteManager().__bases__ == (myfolder.getSiteManager(), )
>>> myfolder.getSiteManager().subs[0] is myfolder11.getSiteManager()
>>> myfolder2.getSiteManager().subs

Let's now move myfolder11 from myfolder to myfolder2:

>>> myfolder2['myfolder21'] = myfolder11
>>> del myfolder['myfolder11']

Now the next site manager for myfolder11's site manager should have changed:

>>> myfolder21 = myfolder11
>>> myfolder21.getSiteManager().__bases__ == (myfolder2.getSiteManager(), )
>>> myfolder2.getSiteManager().subs[0] is myfolder21.getSiteManager()
>>> myfolder.getSiteManager().subs

Make sure that our interfaces and classes are picklable:

>>> import sys
>>> sys.modules['zope.site.tests'].IMyUtility = IMyUtility
>>> IMyUtility.__module__ = 'zope.site.tests'
>>> sys.modules['zope.site.tests'].MyUtility = MyUtility
>>> MyUtility.__module__ = 'zope.site.tests'
>>> from pickle import dumps, loads
>>> data = dumps(myfolder2['myfolder21'])
>>> myfolder['myfolder11'] = loads(data)
>>> myfolder11 = myfolder['myfolder11']
>>> myfolder11.getSiteManager().__bases__ == (myfolder.getSiteManager(), )
>>> myfolder.getSiteManager().subs[0] is myfolder11.getSiteManager()
>>> myfolder2.getSiteManager().subs[0] is myfolder21.getSiteManager()

Finally, let's check that everything works fine when our folder is moved to the folder that doesn't contain any site manager. Our folder's sitemanager's bases should be set to global site manager.

>>> myfolder11.getSiteManager().__bases__ == (myfolder.getSiteManager(), )
>>> nosm = folder.Folder()
>>> nosm['root'] = myfolder11
>>> myfolder11.getSiteManager().__bases__ == (gsm, )


4.0.0a2 (unreleased)

  • Nothing changed yet.

4.0.0a1 (2013-02-20)

  • Added support for Python 3.3.
  • Replaced deprecated zope.interface.implements usage with equivalent zope.interface.implementer decorator.
  • Dropped support for Python 2.4 and 2.5.
  • Include zcml dependencies in configure.zcml, added tests for zcml.

3.9.2 (2010-09-25)

  • Added not declared, but needed test dependency on zope.testing.

3.9.1 (2010-04-30)

  • Removed use of 'zope.testing.doctest' in favor of stdlib's 'doctest.
  • Removed use of 'zope.testing.doctestunit' in favor of stdlib's 'doctest.

3.9.0 (2009-12-29)

  • Avoid a test dependency on zope.copypastemove by testing the correct persistent behavior of a site manager using the normal pickle module.

3.8.0 (2009-12-15)

  • Removed functional testing setup and dependency on zope.app.testing.

3.7.1 (2009-11-18)

  • Moved the zope.site.hooks functionality to zope.component.hooks as it isn't actually dealing with zope.site's concept of a site.
  • Import ISite and IPossibleSite from zope.component after they were moved there from zope.location.

3.7.0 (2009-09-29)

  • Cleaned up the undeclared dependency on zope.app.publication by moving the two relevant subscriber registrations and their tests to that package.
  • Dropped the dependency on zope.traversing which was only used to access zope.location functionality. Configure zope.location for some tests.
  • Demoted zope.configuration to a testing dependency.

3.6.4 (2009-09-01)

  • Set __parent__ and __name__ in the LocalSiteManager's constructor after calling constructor of its superclasses, so __name__ doesn't get overwritten with empty string by the Components constructor.
  • Don't set __parent__ and __name__ attributes of site manager in SiteManagerContainer's setSiteManager method, as they're already set for LocalSiteManager. Other site manager implementations are not required to have those attributes at all, so we're not adding them anymore.

3.6.3 (2009-07-27)

  • Propagate an ObjectRemovedEvent to the SiteManager upon removal of a SiteManagerContainer.

3.6.2 (2009-07-24)

  • Fixed tests to pass with latest packages.
  • Removed failing test of persistent interfaces, since it did not test anything in this package and used the deprecated zodbcode module.
  • Fix NameError when calling zope.site.testing.siteSetUp(site=True).
  • The getNextUtility and queryNextUtility functions was moved to zope.component. While backward-compatibility imports are provided, it's strongly recommended to update your imports.

3.6.1 (2009-02-28)

  • Import symbols moved from zope.traversing to zope.location from the new location.
  • Don't fail when changing component registry bases while moving ISite object to non-ISite object.
  • Allow specify whether to create 'default' SiteManagementFolder on initializing LocalSiteManager. Use the default_folder argument.
  • Add a containment constraint to the SiteManagementFolder that makes it only available to be contained in ILocalSiteManagers and other ISiteManagementFolders.
  • Change package's mailing list address to zope-dev at zope.org, as zope3-dev at zope.org is now retired.
  • Remove old unused code. Update package description.

3.6.0 (2009-01-31)

  • Use zope.container instead of zope.app.container.

3.5.1 (2009-01-27)

  • Extracted from zope.app.component (trunk, 3.5.1 under development) as part of an effort to clean up dependencies between Zope packages.