regex - Email validation using regular expression in JSF 2 / PrimeFaces

Question

I have an input field taking an email address:

<h:inputText value="#{register.user.email}" required="true" />

How can I validate the entered value as a valid email address using regex in JSF 2 / PrimeFaces?

Answer 1

All regular expression attempts to validate the email format based on Latin characters are broken. They do not support internationalized domain names which were available since May 2010. Yes, you read it right, non-Latin characters are since then allowed in domain names and thus also email addresses.

That are thus extremely a lot of possible characters to validate. Best is to just keep it simple. The following regex just validates the email format based on the occurrence of the @ and . characters.

<f:validateRegex pattern="([^.@]+)(.[^.@]+)*@([^.@]+.)+([^.@]+)" />

Again, this just validates the general email format, not whether the email itself is legit. One can still enter aa@bb.cc as address and pass the validation. No one regex can cover that. If the validity of the email address is that important, combine it with an authentication system. Just send some kind of an activation email with a callback link to the email address in question and let the user login by email address.