Laravel 6 将新增为指定队列任务设置中间件的功能

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Taylor Otwell 在 Laravel 6 中新增了为指定队列任务设置中间件的能力，以便我们在执行某些队列任务之前先执行一些业务逻辑：

This [pull request] adds an easy way to have job specific middleware for queued jobs. Global job middleware were actually already possible by calling Bus::pipeThrough([]) in a service provider during the application boot process…These middleware provide a convenient location to wrap jobs in some logic before they are executed.

我们可以在 Job 类中定义 middleware() 方法来设置对应的中间件，该方法返回的是中间件对象实例数组，因此可以定义多个中间件：

public function middleware()
{
   return [new SomeMiddleware];
}

class SomeMiddleware
{
  public function handle($command, $next)
  {
    // Do something...
 
    return $next($command);
  }
}

SomeJob::dispatch()->through([new SomeMiddleware]);