V3 Modelview와 Map<String, String> 질문

public ModelView process(Map<String, String> paramMap) {
    String username = paramMap.get("username");
    int age = Integer.parseInt(paramMap.get("age"));

    Member member = new Member(username, age);
    memberRepository.save(member);

    ModelView mv = new ModelView("save-result");
    mv.getModel().put("member", member);
    return mv;

public class ModelView {
    private String viewName;
    private Map<String, Object> model = new HashMap<>();

    public ModelView(String viewName) {
        this.viewName = viewName;
    }

    public String getViewName() {
        return viewName;
    }

    public void setViewName(String viewName) {
        this.viewName = viewName;
    }

    public Map<String, Object> getModel() {
        return model;
    }

    public void setModel(Map<String, Object> model) {
        this.model = model;
    }

1.Modelview에서 model이 언제생성된거죠..? getmodel을 해주려면 먼저 선언이 되어있는 model을 가지고 반환해줘야하는데 언제선언이 된거죠?

        Map<String, String> paramMap = createParamMap(request);
        ModelView mv = controller.process(paramMap);

        String viewName = mv.getViewName(); //논리이름 new-form
        MyView view = viewResolver(viewName);

        view.render(mv.getModel(), request, response);
    }

    private static MyView viewResolver(String viewName) {
        return new MyView("/WEB-INF/views/" + viewName + ".jsp");
    }

    private static Map<String, String> createParamMap(HttpServletRequest request) {
        Map<String, String> paramMap = new HashMap<>();
        request.getParameterNames().asIterator()
                .forEachRemaining(paramName ->paramMap.put(paramName, request.getParameter(paramName)));
        return paramMap;
    }
}

2. Map<String, String> createMap에서 .forEachRemaining(paramName ->paramMap.put(paramName, request.getParameter(paramName))); 여기를 보면 request.getParmeter(paramName)로 paramName에대한 Value를 가지고오고있는데 여기서 말하는 Value는 age인데 int로 선언하는게 맞지않나요?

항상 답변감사드립니다