JSON schema pattern validation is failing

Question

I am using below pattern in json schema to validate strings.

"pattern": "^(nfs://)(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?).(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?).(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?).(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?):([0-9]{4})"

But currently it is not validating "nfs://172.1.1:2049" as invalid string.

Why does port number have to be four digits? That seems like an error. It could very well be anywhere from 2-5. As far as [a regular expression tester](https://regex101.com) goes, this should work. — tadman, Nov 14 '17 at 05:07
The issue is with ip address. The pattern is matching even if i give only 3 parts of ip. — Anuradha K, Nov 14 '17 at 05:29
Your problem is that you are trying to match 4 groups of numbers between 0 and 255 but `172.1.1` only contains 3 groups. — CAustin, Nov 14 '17 at 05:55

omijn · Answer 1 · 2017-11-14T07:38:15.830

This doesn't immediately seem like an obvious problem, but the . character needs to be escaped because you're trying to literally match that character.

This regex, with escaped . and forward slashes works:

^(nfs:\/\/)(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?):([0-9]{4})

The problem was that since each capturing group that matches digits can match as few as one digit or as many as three, the regex engine looked at the first 1 (in 172), found that it was valid, then tried matching . (any character) and found the digit 7, which is not what you want.

In nfs://172.1.1:2049, the second capturing group in your regex matched the first 1 in the IP address, the . matched the 7, the third capturing group matched the 2.. and so on.

Try it here: https://regex101.com/r/TNXDiQ/1

JSON schema pattern validation is failing

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