regex validation - grails

Question

im pretty new in grails.. im having a little problem right now on validation using matches. What I wanted to happen is that a field can accept combination of alphanumeric and special characters, letters only and numbers only, and if the user inputs special characters only, the system should prompt the user an error. i used matches constraints to validate the data, and im having a hard time how could i set the regex where the field will not accept an input with special characters only. please help me.. thanks a lot for sharing your knowledge.

Answer 1

I think I understand your problem, but correct me if I'm wrong. The input is valid as long as there is at least 1 letter or number, right? In other words, if there isn't a letter or number (only special characters), then the input is invalid?

See if this works:

/^.*[A-Za-z0-9].*$/

Here is my little groovy test:

import java.util.regex.Matcher
import java.util.regex.Pattern

def pattern = ~/^.*[A-Za-z0-9].*$/

assert pattern.matcher("abc").matches()
assert pattern.matcher("ABC").matches()
assert pattern.matcher("abc123").matches()
assert pattern.matcher("123").matches()
assert pattern.matcher("abc!").matches()
assert pattern.matcher("!abc").matches()
assert pattern.matcher("1!bc").matches()
assert pattern.matcher("!.~").matches() == false

Explained:

/             regex start
^             start of string
.*            any character (0 or more times)
[A-Za-z0-9]   at least 1 letter or number
.*            any character (0 or more times)
$             end of string
/             regex end

Answer 2

I don't know if grails supports lookaround, but if it does, this regex will work for you:

/(?=^[\pL\pN!:;]+$)(?!^[!:;]+$)/

explanation:

/                 : regex delimiter
  (?=             : begin positive lookahead
    ^             : start of string
    [\pL\pN!:;]+  : a letter, a digit or a special char one or more times
    $             : end of string
  )               : end of lookahead
  (?!             : begin negative lookahead
    ^             : start of string
    [!:;]+        : a special char one or more times
    $             : end of string
  )               : end of lookahead
/                 : regex delimiter