Théorie générale
Monter une application MVC configurée et prête à être lancée requière de
plus en plus de code au fur et à mesure de l'ajout de fonctionnalités : monter une base
de données, configurer la vue et ses aides, les layouts, enregistrer des plugins, des aides
d'action et bien plus encore...
Aussi, vous réutiliserez souvent le même code dans vos tests, dans une tâche cron ou
encore un service. Il est certes possible d'inclure le script de bootstrap dans de tels cas,
mais souvent des variables seront dépendantes de l'environnement. Par exemple, vous n'aurez
pas besoin de MVC dans une tâche cron, ou alors vous aurez juste besoin
de l'accès à la base de données dans un script de service.
Zend_Application a pour but de simplifier ces processus et de
promouvoir la réutilisabilité de code en encapsulant les étages de définition du bootstrap
en concepts orientés objet (OO).
Zend_Application se décompose en 3 parties :Zend_Application charge l'environnement
PHP, à savoir les include_paths et les autoloads, et instancie
la classe de bootstrap demandée.
Zend_Application_Bootstrap regroupe les interfaces pour les
classes de bootstrap. Zend_Application_Bootstrap_Bootstrap
propose des fonctionnalités de base concernant l'amorçage (le bootstrap), à savoir
des algorithmes de vérification des dépendances et la possibilité de charger des
ressources à la demande.
Zend_Application_Resource est une interface pour les
ressources de bootstrap qui peuvent être chargées à la demande depuis les instances
de bootstrap.
Les développeurs créent une classe de bootstrap pour leur application en étendant
Zend_Application_Bootstrap_Bootstrap ou en implémentant (au minimum)
Zend_Application_Bootstrap_Bootstrapper. Le point d'entrée
(public/index.php) chargera Zend_Application
en l'instanciant et en lui passant :
L'environnement courantDes options de bootstrapping
Les options de bootstrap incluent le chemin vers le fichier contenant la classe de
bootstrap, et optionnellement :
Des include_paths supplémentairesDes espaces de nom d'autoload à enregistrerDes paramètres php.ini à initialiserLe nom de la classe pour le bootstrap (sinon "Bootstrap" sera utilisée)Des paires préfixe / chemin pour les ressources à utiliserN'importe quelle ressource à utiliser (nom de classe ou nom court)Des chemins additionnels vers un fichier de configuration à chargerDes options de configuration supplémentaires
Les options peuvent être un tableau, un objet Zend_Config, ou
le chemin vers un fichier de configuration.
BootstrappingZend_Application's second area of responsibility is
executing the application bootstrap. Bootstraps minimally need to
implement Zend_Application_Bootstrap_Bootstrapper,
which defines the following API:
This API allows the bootstrap to accept the environment and
configuration from the application object, report the resources its
responsible for bootstrapping, and then bootstrap and run the
application.
You can implement this interface on your own, extend
Zend_Application_Bootstrap_BootstrapAbstract, or use
Zend_Application_Bootstrap_Bootstrap.
Besides this functionality, there are a number of other areas of
concern you should familiarize yourself with.
Resource Methods
The Zend_Application_Bootstrap_BootstrapAbstract
implementation provides a simple convention for defining class
resource methods. Any protected method beginning with a name
prefixed with _init will be considered a resource
method.
To bootstrap a single resource method, use the
bootstrap() method, and pass it the name of the
resource. The name will be the method name minus the
_init prefix.
To bootstrap several resource methods, pass an array of names.
Too bootstrap all resource methods, pass nothing.
Take the following bootstrap class:
To bootstrap just the _initFoo() method, do the
following:
bootstrap('foo');
]]>
To bootstrap the _initFoo() and
_initBar() methods, do the following:
bootstrap(array('foo', 'bar'));
]]>
To bootstrap all resource methods, call bootstrap()
with no arguments:
bootstrap();
]]>Bootstraps that use resource plugins
To make your bootstraps more re-usable, we have provided the
ability to push your resources into resource plugin classes.
This allows you to mix and match resources simply via
configuration. We will cover how
to create resources later; in
this section we will show you how to utilize them only.
If your bootstrap should be capable of using resource plugins,
you will need to implement an additional interface,
Zend_Application_Bootstrap_ResourceBootstrapper.
This interface defines an API for locating, registering, and
loading resource plugins:
Resource plugins basically provide the ability to create
resource intializers that can be re-used between applications.
This allows you to keep your actual bootstrap relatively clean,
and to introduce new resources without needing to touch your
bootstrap itself.
Zend_Application_Bootstrap_BootstrapAbstract (and
Zend_Application_Bootstrap_Bootstrap by extension)
implement this interface as well, allowing you to utilize
resource plugins.
To utilize resource plugins, you must specify them in the
options passed to the application object and/or bootstrap. These
options may come from a configuration file, or be passed in
manually. Options will be of key to options pairs, with the key
representing the resource name. The resource name will be the
segment following the class prefix. For example, the resources
shipped with Zend Framework have the class prefix
"Zend_Application_Resource_"; anything following this would
be the name of the resource. As an example,
array(
'FrontController' => array(
'controllerDirectory' => APPLICATION_PATH . '/controllers',
),
),
));
]]>
This indicates that the "FrontController" resource should be
used, with the options specified.
If you begin writing your own resource plugins, or utilize
third-party resource plugins, you will need to tell your
bootstrap where to look for them. Internally, the bootstrap
utilizes Zend_Loader_PluginLoader, so you will only
need to indicate the common class prefix an path pairs.
As an example, let's assume you have custom resource plugins in
APPLICATION_PATH/resources/ and that they share the
common class prefix of My_Resource. You would then
pass that information to the application object as follows:
array(
'My_Resource' => APPLICATION_PATH . '/resources/',
),
'resources' => array(
'FrontController' => array(
'controllerDirectory' => APPLICATION_PATH . '/controllers',
),
),
));
]]>
You would now be able to use resources from that directory.
Just like resource methods, you use the bootstrap()
method to execute resource plugins. Just like with resource
methods, you can specify either a single resource plugin,
multiple plugins (via an array), or all plugins. Additionally,
you can mix and match to execute resource methods as well.
bootstrap('FrontController');
// Execute several:
$bootstrap->bootstrap(array('FrontController', 'Foo'));
// Execute all resource methods and plugins:
$bootstrap->bootstrap();
]]>Resource Registry
Many, if not all, of your resource methods or plugins will
initialize objects, and in many cases, these objects will be
needed elsewhere in your application. How can you access them?
Zend_Application_Bootstrap_BootstrapAbstract
provides a local registry for these objects. To store your
objects in them, you simply return them from your resources.
For maximum flexibility, this registry is referred to as a
"container" internally; its only requirements are that it is an
object. Resources are then registered as properties named after
the resource name. By default, an instance of
Zend_Registry is used, but you may also specify any
other object you wish. The methods setContainer()
and getContainer() may be used to manipulate the
container itself. getResource($resource) can be
used to fetch a given resource from the container, and
hasResource($resource) to check if the resource has
actually been registered.
As an example, consider a basic view resource:
You can then check for it and/or fetch it as follows:
hasResource('view')) {
$view = $bootstrap->getResource('view');
}
// Via the container:
$container = $bootstrap->getContainer();
if (isset($container->view)) {
$view = $container->view;
}
]]>
Please note that the registry and also the container is not global. This
means that you need access to the bootstrap in order to fetch
resources. Zend_Application_Bootstrap_Bootstrap
provides some convenience for this: during its
run() execution, it registers itself as the front
controller parameter "bootstrap", which allows you to fetch it
from the router, dispatcher, plugins, and action controllers.
As an example, if you wanted access to the view resource from
above within your action controller, you could do the following:
getInvokeArg('bootstrap');
$view = $bootstrap->getResource('view');
// ...
}
}
]]>Dependency Tracking
In addition to executing resource methods and plugins, it's
necessary to ensure that these are executed once and once
only; these are meant to bootstrap an application, and
executing multiple times can lead to resource overhead.
At the same time, some resources may depend on other
resources being executed. To solve these two issues,
Zend_Application_Bootstrap_BootstrapAbstract
provides a simple, effective mechanism for dependency
tracking.
As noted previously, all resources -- whether methods or plugins
-- are bootstrapped by calling bootstrap($resource),
where $resource is the name of a resource, an array
of resources, or, left empty, indicates all resources should be
run.
If a resource depends on another resource, it should call
bootstrap() within its code to ensure that resource
has been executed. Subsequent calls to it will then be ignored.
In a resource method, such a call would look like this:
bootstrap('FrontController');
// Retrieve the front controller from the bootstrap registry
$front = $this->getResource('FrontController');
$request = new Zend_Controller_Request_Http();
$request->setBaseUrl('/foo');
$front->setRequest($request);
// Ensure the request is stored in the bootstrap registry
return $request;
}
}
]]>Resource Plugins
As noted
previously, a good way to create re-usable bootstrap resources and to
offload much of your coding to discrete classes is to utilize resource
plugins. While Zend Framework ships with a number of standard
resource plugins, the intention is that developers should write
their own to encapsulate their own initialization needs.
Resources plugins need only implement
Zend_Application_Resource_Resource, or, more simply
still, extend
Zend_Application_Resource_ResourceAbstract. The basic
interface is simply this:
The interface defines simply that a resource plugin should accept options
to the constructor, have mechanisms for setting and retrieving
options, have mechanisms for setting and retrieving the bootstrap
object, and an initialization method.
As an example, let's assume you have a common view intialization you
use in your applications. You have a common doctype, CSS and
JavaScript, and you want to be able to pass in a base document title
via configuration. Such a resource plugin might look like this:
getView();
}
public function getView()
{
if (null === $this->_view) {
$options = $this->getOptions();
$title = '';
if (array_key_exists('title', $options)) {
$title = $options['title'];
unset($options['title']);
}
$view = new Zend_View($options);
$view->doctype('XHTML1_STRICT');
$view->headTitle($title);
$view->headLink()->appendStylesheet('/css/site.css');
$view->headScript()->appendfile('/js/analytics.js');
$viewRenderer =
Zend_Controller_Action_HelperBroker::getStaticHelper(
'ViewRenderer'
);
$viewRenderer->setView($view);
$this->_view = $view;
}
return $this->_view;
}
}
]]>
As long as you register the prefix path for this resource plugin,
you can then use it in your application. Even better, because it
uses the plugin loader, you are effectively overriding the shipped
"View" resource plugin, ensuring that your own is used instead.