HTTP缓存验证

// src/AppBundle/Controller/DefaultController.php
namespace AppBundle\Controller;
 
use Symfony\Component\HttpFoundation\Request;
 
class DefaultController extends Controller
{
    public function homepageAction(Request $request)
    {
        $response = $this->render('static/homepage.html.twig');
        $response->setETag(md5($response->getContent()));
        $response->setPublic(); // make sure the response is public/cacheable
                                // 确保响应是public/cacheable（可缓存的）
        $response->isNotModified($request);
 
        return $response;
    }
}

// src/AppBundle/Controller/ArticleController.php
namespace AppBundle\Controller;
 
// ...
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpFoundation\Request;
use AppBundle\Entity\Article;
 
class ArticleController extends Controller
{
    public function showAction(Article $article, Request $request)
    {
        $author = $article->getAuthor();
 
        $articleDate = new \DateTime($article->getUpdatedAt());
        $authorDate = new \DateTime($author->getUpdatedAt());
 
        $date = $authorDate > $articleDate ? $authorDate : $articleDate;
 
        $response = new Response();
        $response->setLastModified($date);
        // Set response as public. Otherwise it will be private by default.
        // 设置响应为public，Symfony默认将响应设为private
        $response->setPublic();
 
        if ($response->isNotModified($request)) {
            return $response;
        }
 
        // ... do more work to populate the response with the full content
        // ... 做更多处理来将所有的内容都添加到响应中
 
        return $response;
    }
}

// src/AppBundle/Controller/ArticleController.php
namespace AppBundle\Controller;
 
// ...
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpFoundation\Request;
 
class ArticleController extends Controller
{
    public function showAction($articleSlug, Request $request)
    {
        // Get the minimum information to compute
        // the ETag or the Last-Modified value
        // (based on the Request, data is retrieved from
        // a database or a key-value store for instance)
        // 取得“能够计算出Etag或Last-Modified值”的最少信息
        // （基于Request对象，来把数据从数据库[或键值对型数组]中取出）
        $article = ...;
 
        // create a Response with an ETag and/or a Last-Modified header
        // 创建一个响应，令其包含ETag头，或包含Last-Modified头
        $response = new Response();
        $response->setETag($article->computeETag());
        $response->setLastModified($article->getPublishedAt());
 
        // Set response as public. Otherwise it will be private by default.
        // 设置响应为public。Symfony默认将响应设为private
        $response->setPublic();
 
        // Check that the Response is not modified for the given Request
        // 检查响应对于当前Request来说尚未被修改（而直接打出304）
        if ($response->isNotModified($request)) {
            // return the 304 Response immediately 立即返回304
            return $response;
        }
 
        // do more work here - like retrieving more data
        // 做一些事 —— 比如取出更多数据
        $comments = ...;
 
        // or render a template with the $response you've already started
        // 或者用新得到的$response来渲染模板
        return $this->render('article/show.html.twig', array(
            'article' => $article,
            'comments' => $comments
        ), $response);
    }
}