Instantiate request handlers on demand (#12)

* feat: instantiate request handlers on demand (#11)
dogado-group · Nov 29, 2021 · 9eee240 · 9eee240
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## v3.1.0 - 2021-11-XX
+
+- add ability to register request handlers as callable to instantiate them on demand to reduce memory load
+
 ## v3.0.0 - 2021-10-04
 
 - require `dogado/json-api-common:^3.0`

diff --git a/docs/01-json-api-server.md b/docs/01-json-api-server.md
@@ -4,13 +4,13 @@
 
 `Dogado\JsonApi\Server\JsonApiServer`:
 
-| Method                                                      | Return Type            | Description                                                    |
-|-------------------------------------------------------------|------------------------|----------------------------------------------------------------|
-| addHandler(string $type, RequestHandlerInterface $handler)  | void                   | Adds a request handler                                         |
-| createRequestBody(?string $requestBody)                     | DocumentInterface/null | Creates a document from the given string                       |
-| handleRequest(RequestInterface $request)                    | ResponseInterface      | Handles a request to generate a response                       |
-| createResponseBody(ResponseInterface $response)             | string                 | Creates the (http) response body for a given json api response |
-| handleException(\Throwable $throwable, bool $debug = false) | ResponseInterface      | Creates a response for an exception                            |
+| Method                                                              | Return Type            | Description
+|---------------------------------------------------------------------|------------------------|----------------------------------------------------------------
+| addHandler(string $type, RequestHandlerInterface\|callable $handler) | void                   | Adds a request handler. Can be a callable to instantiate request handlers on demand to reduce memory load.
+| createRequestBody(?string $requestBody)                             | DocumentInterface/null | Creates a document from the given string
+| handleRequest(RequestInterface $request)                            | ResponseInterface      | Handles a request to generate a response
+| createResponseBody(ResponseInterface $response)                     | string                 | Creates the (http) response body for a given json api response
+| handleException(\Throwable $throwable, bool $debug = false)         | ResponseInterface      | Creates a response for an exception
 
 ## Table of contents
 
@@ -45,8 +45,8 @@ use Dogado\JsonApi\Model\Request\Request;
 // create the server
 $jsonApi = new JsonApiServer(new Deserializer(), new Serializer());
 
-// add your request handlers to the registry of the json api server
-$jsonApi->addHandler('customResources', new YourCustomRequestHandler());
+// Add your request handlers to the registry of the json api server. You can either pass an instance or a callable.
+$jsonApi->addHandler('customResources', fn () => new YourCustomRequestHandler());
 
 // create the json api request
 $request = new Request(

diff --git a/src/JsonApiServer.php b/src/JsonApiServer.php
@@ -21,6 +21,7 @@
 use Dogado\JsonApi\Serializer\Serializer;
 use Dogado\JsonApi\Server\Decorator\ResponseDecorator;
 use Dogado\JsonApi\Server\RequestHandler\RequestHandlerInterface;
+use RuntimeException;
 use Throwable;
 
 class JsonApiServer
@@ -31,8 +32,11 @@ class JsonApiServer
     protected DocumentSerializerInterface $serializer;
     protected ResponseDecorator $responseDecorator;
 
+    /** @var RequestHandlerInterface[]|callable[] */
+    private array $handlers = [];
+
     /** @var RequestHandlerInterface[] */
-    protected array $handlers = [];
+    private array $handlerInstances = [];
 
     public function __construct(
         ?DocumentDeserializerInterface $deserializer = null,
@@ -44,22 +48,38 @@ public function __construct(
         $this->responseDecorator = $responseDecorator ?? new ResponseDecorator();
     }
 
-    public function addHandler(string $type, RequestHandlerInterface $handler): self
+    public function addHandler(string $type, RequestHandlerInterface|callable $handler): self
     {
         $this->handlers[$type] = $handler;
         return $this;
     }
 
     /**
      * @throws UnsupportedTypeException
+     * @throws RuntimeException
      */
     private function getHandler(string $type): RequestHandlerInterface
     {
+        if (array_key_exists($type, $this->handlerInstances)) {
+            return $this->handlerInstances[$type];
+        }
+
         if (!array_key_exists($type, $this->handlers)) {
             throw new UnsupportedTypeException($type);
         }
 
-        return $this->handlers[$type];
+        $handler = $this->handlers[$type];
+        if (is_callable($handler)) {
+            $handler = $handler();
+
+            if (!$handler instanceof RequestHandlerInterface) {
+                throw new RuntimeException(
+                    'Unable to initialize request handler for type "' . $type . '" by given callable.'
+                );
+            }
+        }
+
+        return ($this->handlerInstances[$type] = $handler);
     }
 
     /**

diff --git a/tests/JsonApiServerTest.php b/tests/JsonApiServerTest.php
@@ -1,4 +1,5 @@
 <?php
+
 namespace Dogado\JsonApi\Server\Tests;
 
 use Dogado\JsonApi\Exception\DocumentSerializerException;
@@ -21,6 +22,7 @@
 use Generator;
 use GuzzleHttp\Psr7\Uri;
 use PHPUnit\Framework\MockObject\MockObject;
+use RuntimeException;
 use Throwable;
 
 class JsonApiServerTest extends TestCase
@@ -34,7 +36,7 @@ class JsonApiServerTest extends TestCase
     /** @var ResponseDecorator|MockObject */
     protected $responseDecorator;
 
-    /** @var RequestHandlerInterface|MockObject */
+    /** @var RequestHandlerInterface|callable|MockObject */
     protected $requestHandler;
 
     protected JsonApiServer $server;
@@ -152,6 +154,29 @@ public function handlerAssociationScenarios(): Generator
         yield ['DELETE', $type, $uri, 'deleteResource'];
     }
 
+    public function testCallableHandlerAssociation(): void
+    {
+        $type = $this->faker()->slug();
+        $uri = sprintf(
+            'http://%s/%s/%s',
+            $this->faker()->domainName(),
+            $type,
+            $this->faker()->numberBetween()
+        );
+
+        $this->server->addHandler($type, fn () => $this->requestHandler);
+
+        $request = new Request('GET', new Uri($uri));
+        $response = $this->createMock(ResponseInterface::class);
+        $this->requestHandler->expects(self::exactly(2))->method('fetchResource')->with($request)
+            ->willReturn($response);
+
+        $this->responseDecorator->expects(self::exactly(2))->method('handle')->with($request, $response);
+        $this->assertEquals($response, $this->server->handleRequest($request));
+        // execute a second time to test caching behaviour
+        $this->assertEquals($response, $this->server->handleRequest($request));
+    }
+
     public function testUnknownType(): void
     {
         $type = $this->faker()->slug();
@@ -166,6 +191,23 @@ public function testUnknownType(): void
         $this->server->handleRequest($request);
     }
 
+    public function testInvalidCallableHandlerInitialization(): void
+    {
+        $type = $this->faker()->slug();
+        $uri = sprintf(
+            'http://%s/%s/%s',
+            $this->faker()->domainName(),
+            $type,
+            $this->faker()->numberBetween()
+        );
+        $request = new Request('GET', new Uri($uri));
+        $this->server->addHandler($type, fn () => $this->faker()->text());
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessageMatches('/Unable to initialize.*by given callable/');
+        $this->server->handleRequest($request);
+    }
+
     public function testInvalidContentType(): void
     {
         $type = $this->faker()->slug();