ValidatingCommandBus for Broadway

broadway.xml

<?xml version="1.0" encoding="utf-8"?>
<container xmlns="http://symfony.com/schema/dic/services"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">

    <services>
        <!-- ... -->
        <service id="broadway.command_handling.validating_command_bus" class="App\Bundle\Broadway\CommandHandling\ValidatingCommandBus" public="false">
            <argument type="service" id="broadway.command_handling.event_dispatching_command_bus"/>
            <argument type="service" id="validator"/>
        </service>
        <service id="broadway.command_handling.command_bus" alias="broadway.command_handling.validating_command_bus"/>
    </services>
</container>

ValidatingCommandBus.php

<?php

namespace App\Bundle\Broadway\CommandHandling;

use App\Bundle\Exception\ValidationFailedException;
use Broadway\CommandHandling\CommandBusInterface;
use Broadway\CommandHandling\CommandHandlerInterface;
use Symfony\Component\Validator\Validator\ValidatorInterface;

class ValidatingCommandBus implements CommandBusInterface
{
    private $commandBus;
    private $validator;

    public function __construct(CommandBusInterface $commandBus, ValidatorInterface $validator)
    {
        $this->commandBus = $commandBus;
        $this->validator = $validator;
    }

    /**
     * {@inheritDoc}
     */
    public function dispatch($command)
    {
        $constraintViolationList = $this->validator->validate($command);
        if (count($constraintViolationList) > 0) {
            throw new ValidationFailedException($constraintViolationList);
        }

        $this->commandBus->dispatch($command);
    }

    /**
     * {@inheritDoc}
     */
    public function subscribe(CommandHandlerInterface $handler)
    {
        $this->commandBus->subscribe($handler);
    }
}