acme_api_register:
    pattern: /user
    defaults: { _controller: AcmeApiBundle:User:post, _format: json }
    requirements:
          _method: POST

<?php

namespace AcmeApiBundleController;

use AcmeApiBundleEntityPatient;
use AcmeApiBundleEntityUser;
use SymfonyBundleFrameworkBundleControllerController;
use SymfonyComponentHttpFoundationRequest;
use SymfonyComponentHttpFoundationResponse;
use FOSRestBundleControllerAnnotationsView;

//use FOSRestBundleViewView;

    class UserController extends Controller
    {
        /**
         * @View()
         */
        public function postAction()
        {
            $user = new Patient();

            $user->setName("Daniel");
            $user->setLastName("My lastName");
            $user->setEmail("pleasework@gmail.com");

            return $user;
        }
    }

sensio_framework_extra:
    view: { annotations: false}
    router: { annotations: true }

fos_rest:
    format_listener:
        rules:
            - prefer_extension: false
    routing_loader:
        default_format: json
    view:
        view_response_listener: force

{
    "name": "symfony/framework-standard-edition",
    "license": "MIT",
    "type": "project",
    "description": "The "Symfony Standard Edition" distribution",
    "autoload": {
        "psr-0": { "": "src/" }
    },
    "require": {
        "php": ">=5.3.3",
        "symfony/symfony": "~2.4",
        "doctrine/orm": "~2.2,>=2.2.3",
        "doctrine/doctrine-bundle": "~1.2",
        "twig/extensions": "~1.0",
        "symfony/assetic-bundle": "~2.3",
        "symfony/swiftmailer-bundle": "~2.3",
        "symfony/monolog-bundle": "~2.4",
        "sensio/distribution-bundle": "~2.3",
        "sensio/framework-extra-bundle": "~3.0",
        "sensio/generator-bundle": "~2.3",
        "incenteev/composer-parameter-handler": "~2.0",
        "friendsofsymfony/rest-bundle": "1.1.*",
        "jms/serializer-bundle": "0.13.*"
    },
    "scripts": {
        "post-install-cmd": [
            "Incenteev\ParameterHandler\ScriptHandler::buildParameters",
            "Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::buildBootstrap",
            "Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::clearCache",
            "Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::installAssets",
            "Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::installRequirementsFile"
        ],
        "post-update-cmd": [
            "Incenteev\ParameterHandler\ScriptHandler::buildParameters",
            "Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::buildBootstrap",
            "Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::clearCache",
            "Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::installAssets",
            "Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::installRequirementsFile"
        ]
    },
    "config": {
        "bin-dir": "bin"
    },
    "extra": {
        "symfony-app-dir": "app",
        "symfony-web-dir": "web",
        "symfony-assets-install": "symlink",
        "incenteev-parameters": {
            "file": "app/config/parameters.yml"
        },
        "branch-alias": {
            "dev-master": "2.4-dev"
        }
    }
}

Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8

fos_rest:
    param_fetcher_listener: true
    format_listener:
        rules:
            fallback_format: json
            prefer_extension: false
            priorities: [json, xml]
    view:
        view_response_listener: force
        formats:
            json: true
            xml: true
            jsonp: false
            rss: false
            html: false
        failed_validation: HTTP_BAD_REQUEST

<?php

    namespace AcmeApiBundleController;

    use AcmeApiBundleEntityPatient;
    use AcmeApiBundleEntityUser;
    use SymfonyComponentHttpFoundationRequest;
    use SymfonyComponentHttpFoundationResponse;
    use FOSRestBundleControllerAnnotationsView;
    use FOSRestBundleControllerFOSRestController;


    class UserController extends FOSRestController
    {
        /**
         * @View()
         */
        public function postUserAction()
        {
            $user = new Patient();

            $user->setName("Daniel");
            $user->setLastName("My lastName");
            $user->setEmail("pleasework@gmail.com");

            return $user;
        }
    }

users:
    type:     rest
    resource: AcmeApiBundleControllerUsersController

#...
fos_rest:
    view:
        view_response_listener: force
    format_listener:
        default_priorities: ['json', 'html', '*/*']
        fallback_format: json
        prefer_extension: true
#...