프론트 컨트롤러 패턴 특징
프론트 컨트롤러 도입
package hello.servlet.web.frontcontroller.v1;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
public interface ControllerV1 {
void process(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException;
}
package hello.servlet.web.frontcontroller.v1;
import hello.servlet.web.frontcontroller.v1.controller.MemberFormControllerV1;
import hello.servlet.web.frontcontroller.v1.controller.MemberListControllerV1;
import hello.servlet.web.frontcontroller.v1.controller.MemberSaveController;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
@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 MemberSaveController());
controllerMap.put("/front-controller/v1/members", new MemberListControllerV1());
}
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("FrontControllerServletV1.service");
String requestURI = request.getRequestURI();
ControllerV1 controller = controllerMap.get(requestURI);
if (controller == null) {
response.setStatus(HttpServletResponse.SC_NOT_FOUND);
return;
}
controller.process(request, response);
}
}
다형성을 위해 인터페이스를 만들고, 각 컨트롤러는 이 인터페이스를 기능에 맞게 구현하면 된다. 인터페이스를 상속받은 프론트 컨트롤러를 통해 로직의 일관성을 가져간다.
‼️ 구조를 건드릴 땐 구조만 건드려야 함 같은 레벨끼리만 개선하기 (기존 코드 최대 유지) ‼️
View 분리
package hello.servlet.web.frontcontroller;
import jakarta.servlet.RequestDispatcher;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
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);
}
}
화면 렌더링을 위한 뷰 객체, 반환 타입이 뷰인 걸 제외하면 프론트 컨트롤러 V1과 동일
Model 추가
컨트롤러 입장에서 HttpServletRequest, HttpServletResponse는 필요하지 않다.
요청 파라미터 정보는 자바의 Map으로 대신 넘기도록 하면 지금 구조에서는 컨트롤러가 서블릿 기술을 몰라도 동작할 수 있다.
request 객체를 model로 사용하는 대신 별도의 model 객체를 만들어서 반환하면 된다.
컨트롤러에서 지정하는 뷰 이름이 중복
컨트롤러는 뷰의 논리 이름을 반환하고, 실제 물리 위치의 이름은 프론트 컨트롤러에서 처리하도록 단순화
package hello.servlet.web.frontcontroller;
import lombok.Getter;
import lombok.Setter;
import java.util.HashMap;
import java.util.Map;
@Getter
@Setter
public class ModelView {
private String viewName;
private Map<String, Object> model = new HashMap<>();
public ModelView(String viewName) {
this.viewName = viewName;
}
}
서블릿의 종속성을 제거하기 위해 Model을 직접 만들고 View 논리 이름까지 전달하는 객체 생성
package hello.servlet.web.frontcontroller.v3;
import hello.servlet.web.frontcontroller.ModelView;
import hello.servlet.web.frontcontroller.MyView;
import hello.servlet.web.frontcontroller.v3.controller.MemberListControllerV3;
import hello.servlet.web.frontcontroller.v3.controller.MemberSaveControllerV3;
import hello.servlet.web.frontcontroller.v3.controller.MemberFormControllerV3;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
@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 {
System.out.println("FrontControllerServletV3.service");
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) {
MyView view = new MyView("/WEB-INF/views/" + viewName + ".jsp");
return view;
}
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
package hello.servlet.web.frontcontroller.v4;
import hello.servlet.web.frontcontroller.ModelView;
import hello.servlet.web.frontcontroller.MyView;
import hello.servlet.web.frontcontroller.v4.controller.MemberFormControllerV4;
import hello.servlet.web.frontcontroller.v4.controller.MemberListControllerV4;
import hello.servlet.web.frontcontroller.v4.controller.MemberSaveControllerV4;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
@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 {
System.out.println("FrontControllerServletv4.service");
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) {
MyView view = new MyView("/WEB-INF/views/" + viewName + ".jsp");
return view;
}
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;
}
}
Model 객체를 프론트 컨트롤러에서 생성해서 넘겨준다. 컨트롤러에서 모델 객체에 값을 담으면 여기에 그대로 담겨있게 된다.
컨트롤러가 직접 뷰의 논리 이름을 반환하므로 이 값을 사용해서 실제 물리 뷰를 찾을 수 있다.
유연한 컨트롤러
프론트 컨트롤러가 다양한 방식의 컨트롤러를 처리할 수 있도록 변경 (호환을 쉽게)
package hello.servlet.web.frontcontroller.v5;
import hello.servlet.web.frontcontroller.ModelView;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
public interface MyHandlerAdapter {
boolean supports(Object handler);
ModelView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws ServletException, IOException;
}
중간에 어뎁터 역할을 함. 다양한 종류의 컨트롤러 호출 가능
컨트롤러의 이름을 더 넓은 범위인 핸들러로 변경. 어뎁터가 있기 때문에 컨트롤러의 개념뿐 아니라 어떤 것이든 해당하는 종류의 어뎁터만 있으면 다 처리 가능
package hello.servlet.web.frontcontroller.v5;
import hello.servlet.web.frontcontroller.ModelView;
import hello.servlet.web.frontcontroller.MyView;
import hello.servlet.web.frontcontroller.v3.controller.MemberFormControllerV3;
import hello.servlet.web.frontcontroller.v3.controller.MemberListControllerV3;
import hello.servlet.web.frontcontroller.v3.controller.MemberSaveControllerV3;
import hello.servlet.web.frontcontroller.v5.adapter.ControllerV3HandlerAdapter;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
@WebServlet(name="frontControllerV5", urlPatterns = "/front-controller/v5/*")
public class FrontControllerV5 extends HttpServlet {
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());
}
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("FrontControllerServletV5.service");
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. handler = " + handler);
}
private Object getHandler(HttpServletRequest request) {
String requestURI = request.getRequestURI();
return handlerMappingMap.get(requestURI);
}
private MyView viewResolver(String viewName) {
MyView view = new MyView("/WEB-INF/views/" + viewName + ".jsp");
return view;
}
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;
}
}