298 lines
10 KiB
Markdown
298 lines
10 KiB
Markdown
[<< previous](12-refactoring.md) | [next >>](14-invoker.md)
|
|
|
|
### Middleware
|
|
|
|
In the last chapter we wrote our RouterClass to implement the middleware interface, and in this chapter I want to explain
|
|
a bit more about what this interface does and why it is used in many applications.
|
|
|
|
The Middlewares are basically a number of wrappers that stand between the client and your application. Each request gets
|
|
passed through all the middlewares, gets handled by our controllers and then the response gets passed back through all
|
|
the middlewars to the client/emitter.
|
|
|
|
So every Middleware can modify the request before it goes on to the next middleware (and finally the handler) and the
|
|
response after it gets created by our handlers.
|
|
|
|
So lets take a look at the middleware and the requesthandler interfaces
|
|
|
|
```php
|
|
interface MiddlewareInterface
|
|
{
|
|
public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface;
|
|
}
|
|
|
|
interface RequestHandlerInterface
|
|
{
|
|
public function handle(ServerRequestInterface $request): ResponseInterface;
|
|
}
|
|
```
|
|
|
|
The RequestHandlerInterface gets only a request and returns a response, the MiddlewareInterface gets a request and a
|
|
requesthandler and returns a response. So the logical thing for the Middleware is to use the handler to produce the
|
|
response.
|
|
|
|
But the middleware could just ignore the handler and produce a response on its own as the interface just requires us
|
|
to produce a response.
|
|
|
|
A simple example for that would be a caching middleware. The basic idea is that we want to cache all request from users
|
|
that are not logged in. This way we can save a lot of processing power in rendering the html and fetching data from the
|
|
database.
|
|
|
|
In this scenario we assume that we have an authentication middleware that checks if a user is logged in and decorates
|
|
the request with an 'isAuthenticated' attribute.
|
|
|
|
If the 'isAuthenticated' attribute is set to false, we check if we have a cached response and return that, if that
|
|
response is not already cached, than we let the handler create the response and store that in the cache for a few
|
|
seconds
|
|
|
|
```php
|
|
interface CacheInterface
|
|
{
|
|
public function get(string $key, callable $resolver, int $ttl): mixed;
|
|
}
|
|
```
|
|
|
|
The first parameter is the identifier for the cache, the second is a callable that produces the value and the last one
|
|
defines the seconds that the cache should keep the item. If the cache doesnt have an item with the given key then it uses
|
|
the callable to produce the value and stores it for the time specified in ttl.
|
|
|
|
so lets write our caching middleware:
|
|
|
|
```php
|
|
final class CachingMiddleware implements MiddlewareInterface
|
|
{
|
|
public function __construct(private CacheInterface $cache){}
|
|
public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
|
|
{
|
|
if ($request->getAttribute('isAuthenticated', false) && $request->getMethod() === 'GET') {
|
|
$key = $request->getUri()->getPath();
|
|
return $this->cache->get($key, fn() => $handler->handle($request), 10);
|
|
}
|
|
return $handler->handle($request);
|
|
}
|
|
}
|
|
```
|
|
|
|
we can also modify the response after it has been created by our application, for example we could implement a gzip
|
|
middleware, or for more simple and silly example a middleware that adds a Dank Meme header to all our response so that the browser
|
|
know that our application is used to serve dank memes:
|
|
|
|
```php
|
|
final class DankMemeMiddleware implements MiddlewareInterface
|
|
{
|
|
public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
|
|
{
|
|
$response = $handler->handle($request);
|
|
return $response->withAddedHeader('Meme', 'Dank');
|
|
}
|
|
}
|
|
```
|
|
|
|
but for our application we are going to just add two external middlewares:
|
|
|
|
* [Trailing-slash](https://github.com/middlewares/trailing-slash) to remove the trailing slash from all routes.
|
|
* [whoops middleware](https://github.com/middlewares/whoops) to wrap our error handler into a nice middleware
|
|
|
|
```bash
|
|
composer require middlewares/trailing-slash
|
|
composer require middlewares/whoops
|
|
```
|
|
|
|
The whoops middleware should be the first middleware to be executed so that we catch any errors that are thrown in the
|
|
application as well as the middleware stack.
|
|
|
|
Our desired request -> response flow looks something like this:
|
|
|
|
Client
|
|
| ^
|
|
v |
|
|
Kernel
|
|
| ^
|
|
v |
|
|
Whoops Middleware
|
|
| ^
|
|
v |
|
|
TrailingSlash
|
|
| ^
|
|
v |
|
|
Routing
|
|
| ^
|
|
v |
|
|
ContainerResolver
|
|
| ^
|
|
v |
|
|
Controller/Action
|
|
|
|
As every middleware expects a RequestHandlerInterface as its second argument we need some extra code that wraps every
|
|
middleware as a RequestHandler and chains them together with the ContainerRouteDecoratedResolver as the last Handler.
|
|
|
|
```php
|
|
interface Pipeline
|
|
{
|
|
public function dispatch(ServerRequestInterface $request): ResponseInterface;
|
|
}
|
|
```
|
|
|
|
And our implementation looks something like this:
|
|
|
|
```php
|
|
<?php declare(strict_types=1);
|
|
|
|
namespace Lubian\NoFramework\Http;
|
|
|
|
use Psr\Container\ContainerInterface;
|
|
use Psr\Http\Message\ResponseInterface;
|
|
use Psr\Http\Message\ServerRequestInterface;
|
|
use Psr\Http\Server\MiddlewareInterface;
|
|
use Psr\Http\Server\RequestHandlerInterface;
|
|
|
|
use function array_reverse;
|
|
use function assert;
|
|
use function is_string;
|
|
|
|
class ContainerPipeline implements Pipeline
|
|
{
|
|
/**
|
|
* @param array<MiddlewareInterface|class-string> $middlewares
|
|
* @param RequestHandlerInterface $tip
|
|
* @param ContainerInterface $container
|
|
*/
|
|
public function __construct(
|
|
private array $middlewares,
|
|
private RequestHandlerInterface $tip,
|
|
private ContainerInterface $container,
|
|
) {
|
|
}
|
|
|
|
public function dispatch(ServerRequestInterface $request): ResponseInterface
|
|
{
|
|
$this->buildStack();
|
|
return $this->tip->handle($request);
|
|
}
|
|
|
|
private function buildStack(): void
|
|
{
|
|
foreach (array_reverse($this->middlewares) as $middleware) {
|
|
$next = $this->tip;
|
|
if ($middleware instanceof MiddlewareInterface) {
|
|
$this->tip = $this->wrapMiddleware($middleware, $next);
|
|
}
|
|
if (is_string($middleware)) {
|
|
$this->tip = $this->wrapResolvedMiddleware($middleware, $next);
|
|
}
|
|
}
|
|
}
|
|
|
|
private function wrapResolvedMiddleware(string $middleware, RequestHandlerInterface $next): RequestHandlerInterface
|
|
{
|
|
return new class ($middleware, $next, $this->container) implements RequestHandlerInterface {
|
|
public function __construct(
|
|
private readonly string $middleware,
|
|
private readonly RequestHandlerInterface $handler,
|
|
private readonly ContainerInterface $container,
|
|
) {
|
|
}
|
|
|
|
public function handle(ServerRequestInterface $request): ResponseInterface
|
|
{
|
|
$middleware = $this->container->get($this->middleware);
|
|
assert($middleware instanceof MiddlewareInterface);
|
|
return $middleware->process($request, $this->handler);
|
|
}
|
|
};
|
|
}
|
|
|
|
private function wrapMiddleware(MiddlewareInterface $middleware, RequestHandlerInterface $next): RequestHandlerInterface
|
|
{
|
|
return new class ($middleware, $next) implements RequestHandlerInterface {
|
|
public function __construct(
|
|
private readonly MiddlewareInterface $middleware,
|
|
private readonly RequestHandlerInterface $handler,
|
|
) {
|
|
}
|
|
|
|
public function handle(ServerRequestInterface $request): ResponseInterface
|
|
{
|
|
return $this->middleware->process($request, $this->handler);
|
|
}
|
|
};
|
|
}
|
|
}
|
|
```
|
|
|
|
Here we define our constructor to require two arguments: an array of middlewares and a requesthandler as the final code
|
|
that should produce our response.
|
|
|
|
In the buildStack() method we wrap every middleware as a RequestHandler with the current tip property as the $next argument
|
|
and store that itself as the current tip.
|
|
|
|
There are of course a lot of more sophisticated ways to build a pipeline/dispatcher that you can check out at the [middlewares github](https://github.com/middlewares/awesome-psr15-middlewares#dispatcher)
|
|
|
|
Lets add a simple factory to our dependencies.php file that creates our middlewarepipeline
|
|
Lets create a simple Factory that loads an Array of Middlewares from the Config folder and uses that to build our pipeline
|
|
|
|
```php
|
|
<?php declare(strict_types=1);
|
|
|
|
namespace Lubian\NoFramework\Factory;
|
|
|
|
use Lubian\NoFramework\Http\ContainerPipeline;
|
|
use Lubian\NoFramework\Http\Pipeline;
|
|
use Lubian\NoFramework\Http\RoutedRequestHandler;
|
|
use Lubian\NoFramework\Settings;
|
|
use Psr\Container\ContainerInterface;
|
|
|
|
class PipelineProvider
|
|
{
|
|
public function __construct(
|
|
private Settings $settings,
|
|
private RoutedRequestHandler $tip,
|
|
private ContainerInterface $container,
|
|
) {
|
|
}
|
|
|
|
public function getPipeline(): Pipeline
|
|
{
|
|
$middlewares = require $this->settings->middlewaresFile;
|
|
return new ContainerPipeline($middlewares, $this->tip, $this->container);
|
|
}
|
|
}
|
|
```
|
|
|
|
And configure the container to use the Factory to create the Pipeline:
|
|
|
|
```php
|
|
...,
|
|
Pipeline::class => fn (PipelineProvider $p) => $p->getPipeline(),
|
|
...
|
|
```
|
|
And of course a new file called middlewares.php in our config folder:
|
|
```php
|
|
<?php declare(strict_types=1);
|
|
|
|
use Lubian\NoFramework\Http\RouteMiddleware;
|
|
use Middlewares\TrailingSlash;
|
|
use Middlewares\Whoops;
|
|
|
|
return [
|
|
Whoops::class,
|
|
TrailingSlash::class,
|
|
RouteMiddleware::class,
|
|
];
|
|
|
|
```
|
|
|
|
And we need to add the pipeline to our Kernel class. I will leave that as an exercise to you, a simple hint that i can
|
|
give you is that the handle()-method of the Kernel should look like this:
|
|
|
|
```php
|
|
public function handle(ServerRequestInterface $request): ResponseInterface
|
|
{
|
|
return $this->pipeline->dispatch($request);
|
|
}
|
|
```
|
|
|
|
Lets try if you can make the kernel work with our created Pipeline implementation. For the future we could improve our
|
|
pipeline a little bit, so that it can accept a class-string of a middleware and resolves that with the help of a
|
|
dependency container, if you want you can do that as well.
|
|
|
|
[<< previous](12-refactoring.md) | [next >>](14-invoker.md)
|