Laravel 4 - 如何将所有字段的所有验证错误消息作为JSON结构返回？

I'm upgrading from Laravel 3 to Laravel 4. My app has some AJAX-only forms that are rendered client-side (i.e. there are no server-side views). Therefore, instead of passing validation errors to views with the I'm upgrading from Laravel 3 to Laravel 4. My a