Passing data between middelware

Question

I use zend-expressive and i would like to pass data from one middelware to another. e.g. in config/routes.php I've

[
    'name' => 'v1.item.list',
    'path' => '/item',
    'allowed_methods' => ['GET'],
    'middleware' => [
        Api\V1\Action\ItemListAction::class,
        Application\Middleware\JsonRenderMiddleware::class
    ]
],

in Api\V1\Action\ItemListAction I'm preparin some data from databases and I like to pass $itemsList to another middelware

public function __invoke(ServerRequestInterface $request, ResponseInterface $response, callable $next = null)
{
    $parameters = new ListParameters($request->getQueryParams());
    $itemsList = $this->commandBus->handle(new ItemListCommand($parameters));
    return $next($request, $response);
}

and in Application\Middleware\JsonRenderMiddleware I would like get $itemsList and return in json format:

public function __invoke(ServerRequestInterface $request, ResponseInterface $response, callable $next = null)
{
    return new JsonResponse($itemsList);
}

How is the best way? Only commandBus or is other solution in this framework?

marcosh · Accepted Answer · 2016-07-29T19:47:51.713

3

You could use the attributes of the $request.

In Api\V1\Action\ItemListAction you could do

$request = $request->withAttribute('list', $itemsList);

and then retrieve it in Application\Middleware\JsonRenderMiddleware using

$itemsList = $request->getAttribute('list');

The only drawback of this solution is that you are creating a dependency between the two middlewares, because the second one will break if the $request does not have a list attribute

edited Jul 29 '16 at 19:47

answered Jul 29 '16 at 14:02

marcosh

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it's doesn't work :/ $response->getAttribute('list'); always returns null even when i try get it right after set it in this same middleware. – quentino Jul 29 '16 at 19:28
Maybe I can not properly understand the idea of middleware. I thought that I can use middleware like some service chain to process data in many ways to receive expected data. Like in this case i want to use different middleware to receive e.g. json or html response, but use this same middleware to retrieve data from DB. – quentino Jul 29 '16 at 19:40
there was a mistake, `getAttribute` needs to be called on `$request`, not on `$response` – marcosh Jul 29 '16 at 19:48
of course I tried it on $request but still dosen't work. Even in this: `$newReqest = $request->withAttribute('data', $item); $data = $newReqest->getAttributes(); return $next($newReqest, $response);` $data is null – quentino Jul 30 '16 at 11:47
ok, now it's works. I had file synchronisation issue with vagrant. Thanks. – quentino Jul 30 '16 at 12:03

score 0 · Answer 2 · answered Jul 29 '16 at 20:07

There are several ways to go here.

Usually you would return a Zend\Diactoros\Response\JsonResponse in your action. Normally you want to extend that class and transform that list into something more useful. I wouldn't use the request to pass data like this.

However I see that you are using a command bus. I haven't worked with that yet, but you might want to have a look at https://github.com/prooph/proophessor-do. That's a nice example on how they use CQRS and Event Sourcing with expressive.

Passing data between middelware

2 Answers2