김영한 - 스프링 MVC 1편 - 백엔드 웹 개발 핵심 기술 3일차

MVC 프레임워크 만들기

 

프론트 컨트롤러 패턴 

 

프론트 컨트롤러 서블릿 하나로 클라이언트 요청을 받음

프론트 컨트롤러 요청에 맞는 컨트롤러를 찾아서 호출

공통 처리 가능

프론트 컨트롤러를 제외한 나머지 컨트롤러는 서블릿을 사용하지 않아도 됨

 

package hello.servlet.web.frontcontroller.v1;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.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.controller;

import hello.servlet.domain.member.Member;
import hello.servlet.domain.member.MemberRepository;
import hello.servlet.web.frontcontroller.v1.ControllerV1;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

public class MemberListControllerV1 implements ControllerV1 {

    private MemberRepository memberRepository = MemberRepository.getInstance();

    @Override
    public void process(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);

    }
}

 

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.MemberSaveControllerV1;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.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> controllerV1Map = new HashMap<>();

    public FrontControllerServletV1() {
        controllerV1Map.put("/front-controller/v1/members/new-form", new MemberFormControllerV1());
        controllerV1Map.put("/front-controller/v1/members/save", new MemberSaveControllerV1());
        controllerV1Map.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 = controllerV1Map.get(requestURI);
        if(controller == null){
            response.setStatus(HttpServletResponse.SC_NOT_FOUND);
            return;
        }

        controller.process(request, response);
    }
}

 

 

urlPatterns = "/front-controller/v1/*" : /front-controller/v1/ 를 포함한 하위 모든 요청은 이 서블릿에서 받아들인다.

 

service()

requestURI를 조회해서 실제 호출할 컨트롤러를 controllerMap에서 차는다. 

만약 없다면 404상태 코드를 반환한다.

컨트롤러를 찾고 controller.process(request, response);을 호출해서 해당 컨트롤러를 실행한다.

 

어댑터 패턴

 

앞에서 개발한 프론트 컨트롤러는 한가지 방식의 컨트롤러 인터페이스만 사용할 수 있다.

어댑터 패턴을 사용해서 프론트 컨트롤러가 다양한 방식의 컨트롤러를 처리 할 수 있게 변경해 보았다.

 

핸들러 어댑터: 어댑터 역할을 해주는 덕분에 다양한 종류의 컨트롤러를 호출할 수 있다.

 

핸들러: 어댑터가 있기 떄문에 컨트롤러의 개념뿐만 아니라 어떠한 것이든 해당하는 종류의 어댑터만 있으면

다 처리할수 있다.

 

 

package hello.servlet.web.frontcontroller.v5;

import hello.servlet.web.frontcontroller.ModelView;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.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;
}

 

package hello.servlet.web.frontcontroller.v5.adapter;

import hello.servlet.web.frontcontroller.ModelView;
import hello.servlet.web.frontcontroller.v3.ControllerV3;
import hello.servlet.web.frontcontroller.v5.MyHandlerAdapter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

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;
    }
}

 

package hello.servlet.web.frontcontroller.v5.adapter;

import hello.servlet.web.frontcontroller.ModelView;
import hello.servlet.web.frontcontroller.v4.ControllerV4;
import hello.servlet.web.frontcontroller.v5.MyHandlerAdapter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

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;
    }
}

 

package hello.servlet.web.frontcontroller.v5;

import hello.servlet.web.frontcontroller.ModelView;
import hello.servlet.web.frontcontroller.MyView;
import hello.servlet.web.frontcontroller.v3.ControllerV3;
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.v4.controller.MemberFormControllerV4;
import hello.servlet.web.frontcontroller.v4.controller.MemberListControllerV4;
import hello.servlet.web.frontcontroller.v4.controller.MemberSaveControllerV4;
import hello.servlet.web.frontcontroller.v5.adapter.ControllerV3HandlerAdapter;
import hello.servlet.web.frontcontroller.v5.adapter.ControllerV4HandlerAdapter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.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 = "frontControllerServletV5",urlPatterns = "/front-controller/v5/*")
public class FrontControllerServletV5 extends HttpServlet {

    private final Map<String, Object> handlerMappingMap = new HashMap<>();
    private final List<MyHandlerAdapter> handlerAdapters = new ArrayList<>();

    public FrontControllerServletV5() {
        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());

        //V4추가
        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); //MemberFormControllerV3() 반환

        if(handler == null){
            response.setStatus(HttpServletResponse.SC_NOT_FOUND);
            return;
        }

        //ControllerV3HandlerAdapter 반환
        MyHandlerAdapter adapter = getHandlerAdapter(handler);

        ModelView mv = adapter.handle(request, response, handler);

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

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

    private MyHandlerAdapter getHandlerAdapter(Object handler) {
        MyHandlerAdapter a;
        for (MyHandlerAdapter adapter : handlerAdapters) {
            if(adapter.supports(handler)){
                return adapter;
            }
        }
        throw new IllegalArgumentException("handler adpater를 찾을 수 없습니다. handler="+ 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");
    }
}

 

생성자

 

 

매핑정보

 

매핑정보의 값이 ControllerV3, ControllerV4 같은 인터페이스에서 아무 값이나 받을 수있는 Object로 변경되었다.

 

핸들러 매핑

 

 

핸들러 매핑 정보인 handlerMappingMap에서 URL에 매핑된 핸들러 객체를 찾아서 반환한다.

 

핸들러를 처리할 수 있는 어댑터 조회

 

 

handler를 처리할 수 있는 어댑터를 adapter.supports(handler)를 통해서 찾는다.

handler가 ControllerV3 인터페이스를 구현했다면, ControllerV3HandlerAdapter 객체가 반환된다.

 

어댑터 호출

 

 

어댑터의 handle(request,response,handler) 메서드를 통해 실제 어댑터가 호출된다.

어댑터는 handler를 호출하고 그 결과를 어댑터에 맞추어 반환한다.

 

 

출처

https://www.inflearn.com/course/%EC%8A%A4%ED%94%84%EB%A7%81-mvc-1