如何在Laravel（Lumen）中的JSON响应中添加ETag标头

Question

I have two routes:

$app->get('time1', function(){
    return response('time1 = '.time());
});
$app->get('time2', function(){
    return response()->json(['time2' => time()]);
});

And one global after-middleware:

public function handle($request, Closure $next)
{
    $response = $next($request);
    $response->setEtag(md5($response->getContent()));
    return $response;
}

In the first case I have this HTTP-header:

ETag:"8114ac3b0aad6e54345ee00f78959316"

But not in the second. Why? How to add the same header in the second case?

Answer 1

The reason you see no ETag in your second response is that this header is stripped by your web server due to the fact that the returned response is compressed by the server - see Content-Encoding: gzip header. The reasoning behind this is that the same resource cannot be byte-for-byte identical given that gzip has various compression levels .

You can either disable gzip compression (check your Apache config, especially config of mod_deflate module) or live without the ETag .

Answer 2

 ....    

  public function handle($request, Closure $next)
  {

    $response = $next($request);

    if ($request->isMethod('GET'))
    {

        $etag = md5($response->getContent());

        $requestETag = str_replace('"', '', $request->getETags());



        if ($requestETag && $requestETag[0] == $etag)
        {

            // Modifies the response so that it conforms to the rules defined for a 304 status code.
            $response->setNotModified();

        }

        $response->setETag($etag);


    }

    return $response;

}