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Table of Contents
In the preceding pages of this section, there has been little to say about where the various files and classes should be located. This is because this depends on the application, library or framework in which you want to use the container. Looking at how the container is configured and built in the Symfony2 full stack framework will help you see how this all fits together, whether you are using the full stack framework or looking to use the service container in another application.
The full stack framework uses the
HttpKernel component to manage the loading
of the service container configuration from the application and bundles and
also handles the compilation and caching. Even if you are not using
it should give you an idea of one way of organizing configuration in a modular
Before building it, the kernel checks to see if a cached version of the container
HttpKernel has a debug setting and if this is false, the
cached version is used if it exists. If debug is true then the kernel
checks to see if configuration is fresh
and if it is, the cached version of the container is used. If not then the container
is built from the application-level configuration and the bundles's extension
Read Dumping the Configuration for Performance for more details.
Application level config is loaded from the
app/config directory. Multiple
files are loaded which are then merged when the extensions are processed. This
allows for different configuration for different environments e.g. dev, prod.
These files contain parameters and services that are loaded directly into the container as per Setting Up the Container with Configuration Files. They also contain configuration that is processed by extensions as per Managing Configuration with Extensions. These are considered to be bundle configuration since each bundle contains an Extension class.
By convention, each bundle contains an Extension class which is in the bundle's
DependencyInjection directory. These are registered with the
when the kernel is booted. When the
ContainerBuilder is compiled,
the application-level configuration relevant to the bundle's extension is
passed to the Extension which also usually loads its own config file(s), typically from the bundle's
Resources/config directory. The application-level config is usually processed
with a Configuration object also stored
in the bundle's
Compiler passes are
used to allow interaction between different bundles as they cannot affect
each other's configuration in the extension classes. One of the main uses is
to process tagged services, allowing bundles to register services to picked
up by other bundles, such as Monolog loggers, Twig extensions and Data Collectors
for the Web Profiler. Compiler passes are usually placed in the bundle's
After the compilation process has loaded the services from the configuration, extensions and the compiler passes, it is dumped so that the cache can be used next time. The dumped version is then used during subsequent requests as it is more efficient.