laravel5.4 Fetch 模式设置问题

Question

我想设置数据库查询结果是一个数据而不是对象的形式。官方文档说5.4开始需要监听新的 IlluminateDatabaseEventsStatementPrepared 事件

Event::listen(StatementPrepared::class, function ($event) {
    $event->statement->setFetchMode(\PDO::FETCH_ASSOC);
});

这段代码加载哪里呢？加在EventServiceProvider.php里吗？为什么我这么加没有效果

<?php

namespace App\Providers;

use Illuminate\Support\Facades\Event;
use Illuminate\Foundation\Support\Providers\EventServiceProvider as ServiceProvider;

class EventServiceProvider extends ServiceProvider
{
    /**
     * The event listener mappings for the application.
     *
     * @var array
     */
    protected $listen = [
        'App\Events\Event' => [
            'App\Listeners\EventListener',
        ],
    ];

    /**
     * Register any events for your application.
     *
     * @return void
     */
    public function boot()
    {
        parent::boot();

        //
        Event::listen(StatementPrepared::class, function ($event) {
            $event->statement->setFetchMode(\PDO::FETCH_ASSOC);
        });
    }
}

找到原因了：需要use Illuminate\Database\Events\StatementPrepared