How to Throw Custom Validation Exception in Laravel Controller

When working with Laravel, you may need to implement custom validation rules and exceptions to enhance the user experience and error handling. In this article, I’ll show you how to throw a custom validation exception in a Laravel controller using a real-world example.

Custom Validation Exception in Laravel

Let’s consider a scenario where you want to validate a user’s input and raise a custom validation exception if the validation fails. In this case, we’ll create a custom validation rule to check whether a user with a specific ‘identifier’ exists in the database. If not, we’ll throw a custom exception.

Here’s a sample code snippet:

public function myFunction(Request $request)
{
    $request->validate([
        'identifier' => 'required'
    ]);
    
    $user = User::whereUsername($request->identifier)->orWhere('email', $request->identifier)->first();

    if (!$user)
        throw ValidationException::withMessages(['identifier' => __('validation.exists', ['attribute' => 'identifier'])]);

    // Perform other actions if validation passes
}

In this code:

1. We start by validating the ‘identifier’ field as required using Laravel’s built-in validation functionality.
2. We then query the database to find a user based on the ‘identifier’ provided in the request. We’re looking for a match either in the ‘username’ or ’email’ columns.
3. If no user is found, we throw a custom validation exception using \Illuminate\Validation\ValidationException::withMessages. We provide an error message key (‘validation.exists’) along with attribute substitution for ‘identifier’  (you can define your own string ). This is a typical way to create custom validation exceptions in Laravel.