Salesforce Apex Rest

@RestResource(urlMapping='/people/v1/*')
global with sharing class PeopleController {

    @HttpGet
    global static void getOnePerson() {


        RestRequest requestContext = RestContext.request;
        RestResponse responseContext = RestContext.response;
        
        // Here we make sure that our response will always be as JSON format.
        responseContext.addHeader('Content-Type', 'application/json');

        try {
            Map<String, String> reqParamsMap = requestContext.params;
            Integer totalParameterExpected = 1;
            if (reqParamsMap.size() != totalParameterExpected) {
                throw new CustomException('We didn\'t receive 1 parameters!');
            }

            if (
                !reqParamsMap.containsKey('personId')
            ) {
                throw new CustomException(
                    'We didn\'t receive all the expected parameters!' + JSON.serialize(reqParamsMap)
                );
            }

            string pPersonId = reqParamsMap.get('personId');

            PersonService personService = new PersonService();
            
            Person objPerson = personService.getOnePersonByPersonId(pPersonId);
            
            List<PeopleDTO> listOfPeopleDTO = new List<PeopleDTO>();
            listOfPeopleDTO.add(objPerson.getDTO());
            
            objResponse.statuscode = 200;
            objResponse.responseBody = Blob.valueOf(JSON.serialize(listOfPeopleDTO));
        } catch (CustomException ex) {
            new HTTPResponseCodeException(400, 'FS-FPC-FE', ex.getMessage())
                .setSFResponseError(objResponse);
        } catch (Exception ex) {
            new HTTPResponseCodeException(
                    500,
                    'FS-FPC-EX',
                    'Error unexpected! [' +
                    ex.getMessage() +
                    '] StackTrace[' +
                    ex.getStackTraceString() +
                    ']'
                )
                .setSFResponseError(objResponse);
        }
    }

}