Regex and negative lookbehind

Posted by peter on Wednesday, February 19, 2014

In my current project our application is built with Spring and we are using a couple of Spring profiles. Unfortunately we didn’t make them unique so if we deploy it with another application in the same application server we might get a name clash. We decided that we better try to use names that are specific for our application. So I started renaming all of our spring profiles by just adding the prefix apigw. to the name so it will be more unique.

auth-http-basic => apigw.auth-http-basic
auth-x509 => apigw.auth-x509

It was pretty easy to search for all occurrences and just add the prefix, totally 52 files and 92 changes. But what if I have missed any change that should have been done? It must be some way to use a regex to search for the string ‘auth-http-basic’ that is not preceded by ‘apigw.’. After a quick search with Google I found the answer; Negative Lookbehind.

“(?<!a)b matches a “b” that is not preceded by an “a”, using negative lookbehind. It doesn’t match cab, but matches the b (and only the b) in bed or debt.(?<=a)b (positive lookbehind) matches the b (and only the b) in cab, but does not match bed or debt.”

This is how the regex looks for me, (?<!apigw.)(auth-http-basic|auth-x509). Just fire up SublimeText and use Find in folder..

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