I am looking for a way to do some string formatting through Grails JSON conversion, similar to custom formatting dates, which I found in this post.

Something like this:

import grails.converters.JSON;

class BootStrap {

     def init = { servletContext ->
         JSON.registerObjectMarshaller(String) {
            return it?.trim()             }
     }
     def destroy = {
     }
}

I know custom formatting can be done on a per domain class basis, but I am looking for a more global solution.