Request validator examples

Interface

interface RequestValidator
{
    /** [@param](https://github.com/param) scalar|array<array-key, scalar|null>|null $parameters */
    public function validateRequest(
        Request $request,
        mixed $parameters,
    ): void;

    /** [@param](https://github.com/param) scalar|array<array-key, scalar|null>|null $parameters */
    public static function areParametersValid(mixed $parameters): bool;
}

See position in process

Scan for viruses in files

You might want to validate files that are uploaded against virus databases before they are given to the business logic. You might have a separate class VirusFreeFile that extends UploadedFile and is constructed as part of the DTO. So you need to do the virus scan process before you construct the command. Your validator might look like the following:

final readonly class VirusFreeFilesRequestValidator implements RequestValidator
{
    public function __construct(
        private VirusScanner $virusScanner,
    ) {
    }

    /** [@param](https://github.com/param) null $parameters */
    public function validateRequest(
        Request $request,
        mixed $parameters,
    ): void {
        foreach ($request->files as $file) {
            // Throws exception if it finds a virus in the file.
            $this->virusScanner->scanFile($file);
        }
    }
    
    /** [@param](https://github.com/param) null $parameters */
    public static function areParametersValid(mixed $parameters): bool
    {
        return $parameters === null;
    }
}

With such a validator in place, there is no way for a file with a virus to reach the business logic. Using such a validator as one of the default validators means you're safe throughout your application.