场景：手头的项目需要对外提供API服务，需要对请求数据进行签名校验。提交接口的数据会有''空字符值存在，laravel的Illuminate\Foundation\Http\Request接收到参数后，会将空字符强制转换为NULL,导致签名校验通不过。

经过一番努力，找到幕后黑手。
Illuminate/Foundation/Http组件中有定义这个中间件。
vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/ConvertEmptyStringsToNull.php

<?phpnamespace Illuminate\Foundation\Http\Middleware;class ConvertEmptyStringsToNull extends TransformsRequest{ /** * Transform the given value. * * @param string $key * @param mixed $value * @return mixed */ protected function transform($key, $value) { return is_string($value) && $value === '' ? null : $value; }}

解决方法：
既然是中间件作祟，肯定在内核中有注册。找到内核注释该中间件就好。
app/Http/Kernel.php

class Kernel extends HttpKernel{ /** * The application's global HTTP middleware stack. * * These middleware are run during every request to your application. * * @var array */ protected $middleware = [ \App\Http\Middleware\CheckForMaintenanceMode::class, \Illuminate\Foundation\Http\Middleware\ValidatePostSize::class, \App\Http\Middleware\TrimStrings::class, //\Illuminate\Foundation\Http\Middleware\ConvertEmptyStringsToNull::class,//会将''转化为null \App\Http\Middleware\TrustProxies::class, \Illuminate\Session\Middleware\StartSession::class, ];