Front Controller 패턴
- 프론트 컨트롤러 서블릿 하나로 클라이언트의 요청을 받음
- 프론트 컨트롤러가 요청에 맞는 컨트롤러를 찾아서 호출
- 입구를 하나로 하고, 공통 처리 가능
- 프론트 컨트롤러를 제외한 나머지 컨트롤러는 서블릿을 사용하지 않아도 됨
프론트 컨트롤러 도입 전
프론트 컨트롤러 도입 후
프론트 컨트롤러 도입 - v1
프론트 컨트롤러 v1 구조
public interface ControllerV1 {
void process(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException;
}
// ---------------------------------------------------------------------------------
@WebServlet(name = "mvcMemberFormServlet", urlPatterns = "/servlet-mvc/members/new-form")
public class MvcMemberFormServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String viewPath = "/WEB-INF/views/new-form.jsp";
RequestDispatcher dispatcher = request.getRequestDispatcher(viewPath);
// dispatcher.forward(): 다른 서블릿이나 JSP로 이동할 수 있는 기능. 서버 내부에서 다시 호출 발생
dispatcher.forward(request, response);
}
}
// ---------------------------------------------------------------------------------
@WebServlet(name = "mvcMemberListServlet", urlPatterns = "/servlet-mvc/members")
public class MvcMemberListServlet extends HttpServlet {
private MemberRepository memberRepository = MemberRepository.getInstance();
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
List<Member> members = memberRepository.findAll();
request.setAttribute("members", members);
String viewPath = "/WEB-INF/views/members.jsp";
RequestDispatcher dispatcher = request.getRequestDispatcher(viewPath);
dispatcher.forward(request, response);
}
}
// ---------------------------------------------------------------------------------
@WebServlet(name = "mvcMemberSaveServlet", urlPatterns = "/servlet-mvc/members/save")
public class MvcMemberSaveServlet extends HttpServlet {
private MemberRepository memberRepository = MemberRepository.getInstance();
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String username = request.getParameter("username");
int age = Integer.parseInt(request.getParameter("age"));
Member member = new Member(username, age);
memberRepository.save(member);
// Model에 데이터 보관
request.setAttribute("member", member);
String viewPath = "/WEB-INF/views/save-result.jsp";
RequestDispatcher dispatcher = request.getRequestDispatcher(viewPath);
dispatcher.forward(request, response);
}
}
// ---------------------------------------------------------------------------------
@WebServlet(name = "frontControllerServletV1", urlPatterns = "/front-controller/v1/*")
public class FrontControllerServletV1 extends HttpServlet {
private Map<String, ControllerV1> controllerMap = new HashMap<>();
public FrontControllerServletV1() {
controllerMap.put("/front-controller/v1/members/new-form", new MemberFormControllerV1());
controllerMap.put("/front-controller/v1/members/save", new MemberSaveControllerV1());
controllerMap.put("/front-controller/v1/members", new MemberListControllerV1());
}
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("FrontControllerServletV1.service");
// http://localhost:8080/front-controller/v1/members/new-form 에서 /front-controller/v1/members/new-form
String requestURI = request.getRequestURI();
ControllerV1 controller = controllerMap.get(requestURI);
if (controller == null) {
response.setStatus(HttpServletResponse.SC_NOT_FOUND);
return;
}
controller.process(request, response);
}
}
View 분리 - v2
View 분리 MVC 패턴 - v2
public class MyView {
private String viewPath;
public MyView(String viewPath) {
this.viewPath = viewPath;
}
public void render(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
RequestDispatcher dispatcher = request.getRequestDispatcher(viewPath);
dispatcher.forward(request, response);
}
}
// ---------------------------------------------------------------------------
public interface ControllerV2 {
MyView process(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException;
}
// ---------------------------------------------------------------------------
@WebServlet(name = "frontControllerServletV2", urlPatterns = "/front-controller/v2/*")
public class FrontControllerServletV2 extends HttpServlet {
private Map<String, ControllerV2> controllerMap = new HashMap<>();
public FrontControllerServletV2() {
controllerMap.put("/front-controller/v2/members/new-form", new MemberFormControllerV2());
controllerMap.put("/front-controller/v2/members/save", new MemberSaveControllerV2());
controllerMap.put("/front-controller/v2/members", new MemberListControllerV2());
}
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String requestURI = request.getRequestURI();
ControllerV2 controller = controllerMap.get(requestURI);
if (controller == null) {
response.setStatus(HttpServletResponse.SC_NOT_FOUND);
return;
}
MyView view = controller.process(request, response);
view.render(request,response);
}
}
// ---------------------------------------------------------------------------
public class MemberSaveControllerV2 implements ControllerV2 {
private MemberRepository memberRepository = MemberRepository.getInstance();
@Override
public MyView process(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String username = request.getParameter("username");
int age = Integer.parseInt(request.getParameter("age"));
Member member = new Member(username, age);
memberRepository.save(member);
request.setAttribute("member", member);
return new MyView("/WEB-INF/views/save-result.jsp");
}
}
Model 추가 - v3
- 서블릿 종속성 제거: 컨트롤러의 Request, Response 객체 제거. 요청 정보는 자바의 Map으로 대신 넘기도록 함.
-> request 객체를 Model로 사용하는 대신, 별도의 Model 객체를 만들어서 반환
- 뷰 이름 중복 제거: /WEB-INF/views 같은 중복되는 경로 제거. 컨트롤러가 뷰의 논리 이름을 반환하면, 뷰 리졸버가 물리 위치를 만들고 이를 프론트 컨트롤러가 처리.
Model 추가 MVC 패턴 - v3
@Getter @Setter
public class ModelView {
private String viewName;
private Map<String, Object> model = new HashMap<>();
public ModelView(String viewName) {
this.viewName = viewName;
}
}
// --------------------------------------------------------------------
public interface ControllerV3 {
ModelView process(Map<String, String> paramMap);
}
// --------------------------------------------------------------------
public class MyView {
private String viewPath;
public MyView(String viewPath) {
this.viewPath = viewPath;
}
public void render(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
RequestDispatcher dispatcher = request.getRequestDispatcher(viewPath);
dispatcher.forward(request, response);
}
public void render(Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
modelToRequestAttribute(model, request);
RequestDispatcher dispatcher = request.getRequestDispatcher(viewPath);
dispatcher.forward(request, response);
}
private void modelToRequestAttribute(Map<String, Object> model, HttpServletRequest request) {
model.forEach((key, value) -> request.setAttribute(key, value));
}
}
// --------------------------------------------------------------------
public class MemberSaveControllerV3 implements ControllerV3 {
private MemberRepository memberRepository = MemberRepository.getInstance();
@Override
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;
}
}
// --------------------------------------------------------------------
@WebServlet(name = "frontControllerServletV3", urlPatterns = "/front-controller/v3/*")
public class FrontControllerServletV3 extends HttpServlet {
private Map<String, ControllerV3> controllerMap = new HashMap<>();
public FrontControllerServletV3() {
controllerMap.put("/front-controller/v3/members/new-form", new MemberFormControllerV3());
controllerMap.put("/front-controller/v3/members/save", new MemberSaveControllerV3());
controllerMap.put("/front-controller/v3/members", new MemberListControllerV3());
}
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String requestURI = request.getRequestURI();
ControllerV3 controller = controllerMap.get(requestURI);
if (controller == null) {
response.setStatus(HttpServletResponse.SC_NOT_FOUND);
return;
}
Map<String, String> paramMap = createParamMap(request);
ModelView mv = controller.process(paramMap);
String viewName = mv.getViewName();
MyView view = viewResolver(viewName);
view.render(mv.getModel(), request,response);
}
private MyView viewResolver(String viewName) {
return new MyView("/WEB-INF/views/" + viewName + ".jsp");
}
private 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;
}
}
단순하고 실용적인 컨트롤러 - v4
- 항상 ModelView 객체를 생성하고 반환해야 하는 부분이 번거롭다. -> 개발자가 사용하기 불편함.
- 프론트 컨트롤러가 컨트롤러에 빈 Model을 생성해서 전달해줌. 컨트롤러는 Model에 바로 데이터를 추가해주면 됨.
MVC 패턴 - v4
public interface ControllerV4 {
public String process(Map<String, String> paramMap, Map<String, Object> model);
}
// ---------------------------------------------------------------------------------
@WebServlet(name = "frontControllerServletV4", urlPatterns = "/front-controller/v4/*")
public class FrontControllerServletV4 extends HttpServlet {
private Map<String, ControllerV4> controllerMap = new HashMap<>();
public FrontControllerServletV4() {
controllerMap.put("/front-controller/v4/members/new-form", new MemberFormControllerV4());
controllerMap.put("/front-controller/v4/members/save", new MemberSaveControllerV4());
controllerMap.put("/front-controller/v4/members", new MemberListControllerV4());
}
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String requestURI = request.getRequestURI();
ControllerV4 controller = controllerMap.get(requestURI);
if (controller == null) {
response.setStatus(HttpServletResponse.SC_NOT_FOUND);
return;
}
Map<String, String> paramMap = createParamMap(request);
Map<String, Object> model = new HashMap<>();
String viewName = controller.process(paramMap, model);
MyView view = viewResolver(viewName);
view.render(model, request,response);
}
private MyView viewResolver(String viewName) {
return new MyView("/WEB-INF/views/" + viewName + ".jsp");
}
private 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;
}
}
// ---------------------------------------------------------------------------------
public class MemberSaveControllerV4 implements ControllerV4 {
private MemberRepository memberRepository = MemberRepository.getInstance();
@Override
public String process(Map<String, String> paramMap, Map<String, Object> model) {
String username = paramMap.get("username");
int age = Integer.parseInt(paramMap.get("age"));
Member member = new Member(username, age);
memberRepository.save(member);
model.put("member", member);
return "save-result";
}
}
유연한 컨트롤러1 - v5
- 정해진 Controller가 아니라, 다양한 종류의 Controller(ControllerV1 or ControllerV4)를 쓰고 싶은 경우가 있다.
- v4 패턴은 사용할 수 있는 Controller 인터페이스가 정해져 있어서 유연하지 않다.
- 이를 해결하기 위해 어댑터 패턴을 적용해서, 다양한 방식의 컨트롤러를 처리할 수 있도록 한다.
- 컨트롤러의 이름을 핸들러로 변경함. -> 어떠한 종류의 핸들러든 처리할 수 있기 때문에, 의미를 넓히기 위함.
유연한 컨트롤러 MVC 패턴 - v5
public interface MyHandlerAdapter {
boolean supports(Object handler);
ModelView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws ServletException, IOException;
}
// ------------------------------------------------------------------------------------
public class ControllerV3HandlerAdapter implements MyHandlerAdapter {
@Override
public boolean supports(Object handler) {
return (handler instanceof ControllerV3);
}
@Override
public ModelView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws ServletException, IOException {
ControllerV3 controller = (ControllerV3) handler;
Map<String, String> paramMap = createParamMap(request);
ModelView mv = controller.process(paramMap);
return mv;
}
private 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;
}
}
// ------------------------------------------------------------------------------------
@WebServlet(name = "frontControllerV5", urlPatterns = "/front-controller/v5/*")
public class FrontControllerV5 extends HttpServlet {
// 모든 컨트롤러(핸들러) 지원하기 위해 Object로
private final Map<String, Object> handlerMappingMap = new HashMap<>();
private final List<MyHandlerAdapter> handlerAdapters = new ArrayList<>();
public FrontControllerV5() {
initHandlerMappingMap();
initHandlerAdapters();
}
private void initHandlerMappingMap() {
handlerMappingMap.put("/front-controller/v5/v3/members/new-form", new MemberFormControllerV3());
handlerMappingMap.put("/front-controller/v5/v3/members/save", new MemberSaveControllerV3());
handlerMappingMap.put("/front-controller/v5/v3/members", new MemberListControllerV3());
}
private void initHandlerAdapters() {
handlerAdapters.add(new ControllerV3HandlerAdapter());
}
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Object handler = getHandler(request);
if (handler == null) {
response.setStatus(HttpServletResponse.SC_NOT_FOUND);
return;
}
MyHandlerAdapter adapter = getHandlerAdapter(handler);
ModelView mv = adapter.handle(request, response, handler);
String viewName = mv.getViewName();
MyView view = viewResolver(viewName);
view.render(mv.getModel(), request, response);
}
private MyHandlerAdapter getHandlerAdapter(Object handler) {
for (MyHandlerAdapter adapter : handlerAdapters) {
if (adapter.supports(handler)) {
return adapter;
}
}
throw new IllegalArgumentException("handler adapter를 찾을 수 없습니다. hadler = " + handler);
}
private Object getHandler(HttpServletRequest request) {
String requestURI = request.getRequestURI();
return handlerMappingMap.get(requestURI);
}
private MyView viewResolver(String viewName) {
return new MyView("/WEB-INF/views/" + viewName + ".jsp");
}
}
유연한 컨트롤러2 - v5
- v3 외에도, ControllerV4도 추가해보자.
@WebServlet(name = "frontControllerV5", urlPatterns = "/front-controller/v5/*")
public class FrontControllerV5 extends HttpServlet {
// 모든 컨트롤러(핸들러) 지원하기 위해 Object로
private final Map<String, Object> handlerMappingMap = new HashMap<>();
private final List<MyHandlerAdapter> handlerAdapters = new ArrayList<>();
public FrontControllerV5() {
initHandlerMappingMap();
initHandlerAdapters();
}
private void initHandlerMappingMap() {
handlerMappingMap.put("/front-controller/v5/v3/members/new-form", new MemberFormControllerV3());
handlerMappingMap.put("/front-controller/v5/v3/members/save", new MemberSaveControllerV3());
handlerMappingMap.put("/front-controller/v5/v3/members", new MemberListControllerV3());
handlerMappingMap.put("/front-controller/v5/v4/members/new-form", new MemberFormControllerV4());
handlerMappingMap.put("/front-controller/v5/v4/members/save", new MemberSaveControllerV4());
handlerMappingMap.put("/front-controller/v5/v4/members", new MemberListControllerV4());
}
private void initHandlerAdapters() {
handlerAdapters.add(new ControllerV3HandlerAdapter());
handlerAdapters.add(new ControllerV4HandlerAdapter());
}
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Object handler = getHandler(request);
if (handler == null) {
response.setStatus(HttpServletResponse.SC_NOT_FOUND);
return;
}
MyHandlerAdapter adapter = getHandlerAdapter(handler);
ModelView mv = adapter.handle(request, response, handler);
String viewName = mv.getViewName();
MyView view = viewResolver(viewName);
view.render(mv.getModel(), request, response);
}
private MyHandlerAdapter getHandlerAdapter(Object handler) {
for (MyHandlerAdapter adapter : handlerAdapters) {
if (adapter.supports(handler)) {
return adapter;
}
}
throw new IllegalArgumentException("handler adapter를 찾을 수 없습니다. hadler = " + handler);
}
private Object getHandler(HttpServletRequest request) {
String requestURI = request.getRequestURI();
return handlerMappingMap.get(requestURI);
}
private MyView viewResolver(String viewName) {
return new MyView("/WEB-INF/views/" + viewName + ".jsp");
}
}
// --------------------------------------------------------------------------------
public class ControllerV4HandlerAdapter implements MyHandlerAdapter {
@Override
public boolean supports(Object handler) {
return (handler instanceof ControllerV4);
}
@Override
public ModelView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws ServletException, IOException {
ControllerV4 controller = (ControllerV4) handler;
Map<String, String> paramMap = createParamMap(request);
Map<String, Object> model = new HashMap<>();
String viewName = controller.process(paramMap, model);
ModelView mv = new ModelView(viewName);
mv.setModel(model);
return mv;
}
private 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;
}
}
