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.ADI = mask(data.ADI, 1, 2)
  data.SOYADI = mask(data.SOYADI, 1, 2)
  data.NUMARA = mask(data.NUMARA, 1, 2)
} 

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