**Course Title:** Mastering Symfony: Building Enterprise-Level PHP Applications **Section Title:** API Platform and GraphQL **Topic:** Build a fully-featured API using API Platform with pagination, filtering, and GraphQL support.(Lab topic) **Objective:** By the end of this topic, you will be able to design, build, and deploy a fully-featured API using API Platform, with support for pagination, filtering, and GraphQL queries. **Prerequisites:** - Familiarity with Symfony framework and its components - Understanding of REST principles and API development - Experience with Symfony controllers, serializer component, and API authentication **Introduction:** API Platform is a powerful tool for building robust, scalable, and maintainable APIs in Symfony. In this topic, we will explore how to use API Platform to build a fully-featured API with support for pagination, filtering, and GraphQL queries. **Step 1: Setting up API Platform** To start building our API, we need to install API Platform using Composer: ```bash composer require api-platform/core ``` Next, we need to configure API Platform by creating a `config/packages/api_platform.yaml` file: ```yaml api_platform: default_platform: 'api_platform' platforms: api_platform: routes: resource_class: 'ApiPlatform\Core\Resource\ResourceClass' route_prefix: '/api' ``` **Step 2: Defining our API Entities** We need to define our API entities using the `ApiPlatform\Core\Entity\Entity` class: ```php // src/Entity/User.php namespace App\Entity; use ApiPlatform\Core\Annotation\ApiResource; use ApiPlatform\Core\Annotation\Filter; use ApiPlatform\Core\Annotation\Search; use Doctrine\ORM\Mapping as ORM; /** * @ApiResource * @Filter("Range") * @Search("fulltext") */ class User { /** * @ORM\Id * @ORM\GeneratedValue * @ORM\Column(type="integer") */ private $id; /** * @ORM\Column(type="string") */ private $name; /** * @ORM\Column(type="string") */ private $email; // getters and setters } ``` **Step 3: Creating our API Controller** We need to create an API controller that will handle our API requests: ```php // src/Controller/UserController.php namespace App\Controller; use App\Entity\User; use ApiPlatform\Core\Controller\ApiPlatformController; use ApiPlatform\Core\Serializer\SerializerInterface; class UserController extends ApiPlatformController { private $serializer; public function __construct(SerializerInterface $serializer) { $this->serializer = $serializer; } /** * @GET("/users", name="get_users") */ public function getUsers(): Response { $users = $this->getDoctrine()->getRepository(User::class)->findAll(); return $this->json($users, 200); } /** * @GET("/users/{id}", name="get_user") */ public function getUser($id): Response { $user = $this->getDoctrine()->getRepository(User::class)->find($id); return $this->json($user, 200); } /** * @POST("/users", name="create_user") */ public function createUser(User $user): Response { $this->getDoctrine()->getManager()->persist($user); $this->getDoctrine()->getManager()->flush(); return $this->json($user, 201); } /** * @PUT("/users/{id}", name="update_user") */ public function updateUser(User $user): Response { $this->getDoctrine()->getManager()->persist($user); $this->getDoctrine()->getManager()->flush(); return $this->json($user, 200); } /** * @DELETE("/users/{id}", name="delete_user") */ public function deleteUser($id): Response { $user = $this->getDoctrine()->getRepository(User::class)->find($id); if ($user) { $this->getDoctrine()->getManager()->remove($user); $this->getDoctrine()->getManager()->flush(); } return $this->json(['message' => 'User deleted successfully'], 200); } } ``` **Step 4: Adding Pagination, Filtering, and GraphQL Support** To add pagination, filtering, and GraphQL support to our API, we need to use the `ApiPlatform\Core\Serializer\SerializerInterface` to serialize our data. First, we need to add pagination support: ```php // src/Controller/UserController.php use ApiPlatform\Core\Serializer\SerializerInterface; class UserController extends ApiPlatformController { private $serializer; public function __construct(SerializerInterface $serializer) { $this->serializer = $serializer; } /** * @GET("/users", name="get_users") */ public function getUsers(int $page = 1, int $limit = 10): Response { $users = $this->getDoctrine()->getRepository(User::class)->paginate($page, $limit); return $this->json($users, 200); } /** * @GET("/users/{id}", name="get_user") */ public function getUser($id): Response { $user = $this->getDoctrine()->getRepository(User::class)->find($id); return $this->json($user, 200); } /** * @POST("/users", name="create_user") */ public function createUser(User $user): Response { $this->getDoctrine()->getManager()->persist($user); $this->getDoctrine()->getManager()->flush(); return $this->json($user, 201); } /** * @PUT("/users/{id}", name="update_user") */ public function updateUser(User $user): Response { $this->getDoctrine()->getManager()->persist($user); $this->getDoctrine()->getManager()->flush(); return $this->json($user, 200); } /** * @DELETE("/users/{id}", name="delete_user") */ public function deleteUser($id): Response { $user = $this->getDoctrine()->getRepository(User::class)->find($id); if ($user) { $this->getDoctrine()->getManager()->remove($user); $this->getDoctrine()->getManager()->flush(); } return $this->json(['message' => 'User deleted successfully'], 200); } } ``` Next, we need to add filtering support: ```php // src/Controller/UserController.php use ApiPlatform\Core\Serializer\SerializerInterface; class UserController extends ApiPlatformController { private $serializer; public function __construct(SerializerInterface $serializer) { $this->serializer = $serializer; } /** * @GET("/users", name="get_users") */ public function getUsers(int $page = 1, int $limit = 10, string $filter = null): Response { $users = $this->getDoctrine()->getRepository(User::class)->paginate($page, $limit); if ($filter) { $users = $users->filterBy($filter); } return $this->json($users, 200); } /** * @GET("/users/{id}", name="get_user") */ public function getUser($id): Response { $user = $this->getDoctrine()->getRepository(User::class)->find($id); return $this->json($user, 200); } /** * @POST("/users", name="create_user") */ public function createUser(User $user): Response { $this->getDoctrine()->getManager()->persist($user); $this->getDoctrine()->getManager()->flush(); return $this->json($user, 201); } /** * @PUT("/users/{id}", name="update_user") */ public function updateUser(User $user): Response { $this->getDoctrine()->getManager()->persist($user); $this->getDoctrine()->getManager()->flush(); return $this->json($user, 200); } /** * @DELETE("/users/{id}", name="delete_user") */ public function deleteUser($id): Response { $user = $this->getDoctrine()->getRepository(User::class)->find($id); if ($user) { $this->getDoctrine()->getManager()->remove($user); $this->getDoctrine()->getManager()->flush(); } return $this->json(['message' => 'User deleted successfully'], 200); } } ``` Finally, we need to add GraphQL support: ```php // src/Controller/UserController.php use ApiPlatform\Core\Serializer\SerializerInterface; use GraphQL\Type\Definition\Type; use GraphQL\Type\Definition\ObjectType; use GraphQL\Type\Definition\Field; use GraphQL\Type\Definition\InputObjectType; class UserController extends ApiPlatformController { private $serializer; public function __construct(SerializerInterface $serializer) { $this->serializer = $serializer; } /** * @GET("/graphql", name="graphql") */ public function getGraphQL(): Response { $schema = new GraphQLSchema([ 'query' => new ObjectType([ 'name' => 'User', 'fields' => [ new Field('id', Type::int()), new Field('name', Type::string()), new Field('email', Type::string()), ], ]), 'mutation' => new ObjectType([ 'name' => 'User', 'fields' => [ new Field