Bootstrapping¶

The FLOW3 Application Context¶

Each request, no matter if it runs from the command line or through HTTP, runs in a specific application context. FLOW3 provides exactly three built-in contexts:

• Development (default) - used for development
• Production - should be used for a live site
• Testing - is used for functional tests

The context FLOW3 runs in is specified through the environment variable FLOW3_CONTEXT. It can be set per command at the command line or be part of the webserver configuration:

# run the FLOW3 CLI commands in production context FLOW3_CONTEXT=Production ./flow3 help

# In your Apache configuration, you usually use: SetEnv FLOW3_CONTEXT Production

Boot Sequence¶

There are basically two types of requests which are handled by a FLOW3 application: command line and HTTP requests:

• command line requests are passed to the flow3.php script which resides in the Scripts folder of the FLOW3 package
• HTTP requests are first taken care of by the index.php script residing in the public Web directory.

Both scripts set certain environment variables and then instantiate and run the TYPO3\FLOW3\Core\Bootstrap class.

The bootstrap’s run() method initializes the bare minimum needed for any kind of operation. When it did that, it determines the actual request handler which takes over the control of the further boot sequence and handling the request.

public function run() {
        Scripts::initializeClassLoader($this);
        Scripts::initializeSignalSlot($this);
        Scripts::initializePackageManagement($this);

        $this->activeRequestHandler = $this->resolveRequestHandler();
        $this->activeRequestHandler->handleRequest();
}

The request handler in charge executes a sequence of steps which need to be taken for initializing FLOW3 for the purpose defined by the specialized request handler. FLOW3’s Bootstrap class provides convenience methods for building such a sequence and the result can be customized by adding further or removing unnecessary steps.

After initialization, the request handler takes the necessary steps to handle the request, does or does not echo a response and finally exits the application. Control is not returned to the bootstrap again, but a request handler should call the bootstrap’s shutdown() method in order to cleanly shut down important parts of the framework.

Run Levels¶

There are two pre-defined levels to which FLOW3 can be initialized:

• compiletime brings FLOW3 into a state which allows for code generation and other low-level tasks which can only be done while FLOW3 is not yet fully ready for serving user requests. Compile time has only limited support for Dependency Injection and lacks support for many other functions such as Aspect-Oriented Programming and Security.
• runtime brings FLOW3 into a state which is fully capable of handling user requests and is optimized for speed. No changes to any of the code caches or configuration related to code is allowed during runtime.

The bootstrap’s methods buildCompiletimeSequence() and buildRuntimeSequence() conveniently build a sequence which brings FLOW3 into either state on invocation.

Request Handlers¶

A request handler is in charge of executing the boot sequence and ultimately answering the request it was designed for. It must implement the \TYPO3\FLOW3\Core\RequestHandlerInterface interface which, among others, contains the following methods:

public function handleRequest();

public function canHandleRequest();

public function getPriority();

On trying to find a suitable request handler, the bootstrap asks each registered request handler if it can handle the current request – canHandleRequest() – and if it can, how eager it is to do so – getPriority(). It then passes control to the request handler which is most capable of responding to the request – handleRequest().

Request handlers must first be registered in order to be considered during the resolving phase. Registration is done in the Package class of the package containing the request handler:

class Package extends BasePackage {

        public function boot(\TYPO3\FLOW3\Core\Bootstrap $bootstrap) {
                $bootstrap->registerRequestHandler(new \Acme\Foo\BarRequestHandler($bootstrap));
        }

}