Question

I have a regular expression I am trying to use to rewrite an incoming REST url and am getting stuck on one use case when one section of the URL is excluded.

Here is the regex I’m currently using:

^(/[^/]+/(?:books))/([^/]+?)(?:/(?:(?!page).+?))?(?:/page/(\\d+))?$

As example I’m using “$1 – $2 – $3” as parts to use in writing new URL.

Here are the examples that are working correctly…

"/mySite/books/topic1/page/2" results in "/mySite/books - topic1 - 2"
"/mySite/books/topic1/subtopic1/page/2" results in "/mySite/books - topic1 - 2"

All the above work as intended. The problem is when the URL excludes the “topic1” part of the URL then the results are not what I need. Example:

"/mySite/books/page/2" results in "/mySite/books - page - "

What I need is the $2 to be blank, because there is no topic, and the page number still as $3. What I need as output…

"/mySite/books/page/2" results in "/mySite/books -  - 2"

What can I change in my regex to satisfy that scenario without disrupting the existing ones that work correctly? This is being done in Java.

Answer 1

You might try to use regex pattern

^(/[^/]+/books)/(?:(?!page/)([^/]+)/)?page/(\\d+)$