Question

I am validating some input from a Restlet URL in a utility method (that way if the behavior I take changes, I only change it one place, yay). The legalName essentially validates the value as being alphaNumeric, but I may allow other characters soon.

I try to keep my Exceptions to make sense – what Exception would be the best in this scenario?

public static String getProperty(Request request, String key) {
    String value = request.getAttributes().get(key).toString();
    // unless something is specifically text, it is a property
    if(legalName(value)) return value;
    throw new IllegalArgumentException(value);

}

My thoughts are:

• IllegalArgumentException – the key directly leads to an invalid result
• IllegalStateException – we’re trying to use a non-conforming value
• No exception – return an empty string and log the fact that a breach was made
• No exception – remove any undesireable characters, return the sanitized string, and log the fact

Surely I’m not the first person to have to validate input before 🙂

Answer 1

Exceptions like this should be thrown when the property is stored, not retrieved. Check Restlet validation for that.

If you prefer to stick to your solution:

• rename the method to validateName(..) and let it throw the exception. If it doesn’t – return the value.
• javax.validation.ValidationException looks the better option, but you can use any of the two IllegalXException you mentioned. Just make sure they have a more detailed message.