Question

I seek the best way to handle error validation in the @service layer in a spring mvc application.

I have a @Controller and a @Service class.

My controller :

public String saveProduct(Product product) {
    myService.saveProduct(product);
    return "view";
}

My service :

public void saveProduct(Product product) {
    // some validation here
    myDao.save(product);
}

Now let’s say that the validation leads to 2 or 3 errors (the color is not appropriate, the supplier can’t deliver the product right now, and so on…) and I have to display all of them at the same time.

How do I transmit those errors to my controller, and then to my jsp ? Using an “Errors” object ? An exception containing all those errors ?

I’ve already looked here : Passing errors back to the view from the service layer but I can’t find a convenient answer. Do I really have to create unchecked exceptions for EACH error ? And what if I have a 20 or 30 errors ?

Answer 1

Finally I created a custom exception to handle the functional errors :

public class ServiceException extends Exception {  
    private List<String> errors = new ArrayList<>();
    (...)
}

I also created a ValidationErrorsHelper class with the following method :

public static void rejectErrors(final BindingResult result, final List<String> errors) {
    if (errors != null) {
        for (final String error : errors) {
            result.reject(error);
        }
    }
}

And in my controller class, I catch the exception :

try {
    this.myService.myFunction(...);
} catch (final ServiceException e) {
    ValidationErrorsHelper.rejectErrors(result, e.getErrors());
}

This is the best way I could find. If there’s any better suggestion I’m all ears !