DB2API Masked Transmission of Data in a Web Service Response

import groovy.json.JsonOutput;

def parser = new groovy.json.JsonSlurper();
def jsonResp = parser.parseText(responseBodyTextToClient);

static String mask(String input, int exceptFirst, int exceptLast) {
String regex="(?<=.{" + exceptFirst + "}).(?=.{"+ exceptLast + "})";
    return input.replaceAll(regex, "*");
}

for(Object data in jsonResp.data) { 
  data.NAME = mask(data.NAME,1,2)
  data.SURNAME = mask(data.SURNAME,1,2)
  data.PHONENUMBER= mask(data.PHONENUMBER,1,2)
} 

responseBodyTextToClient=JsonOutput.prettyPrint(JsonOutput.toJson(jsonResp))