스프링 MVC 6일차_MVC 프레임워크 만들기_2

# MVC 프레임워크 만들기_2

##  단순하고 실용적인 컨트롤러_V4

• 좋은 프레임워크는 아키텍처도 중요하지만, 그와 더불어 개발자가 단순하고 편리하게 사용할 수 있어야 함. (실용성)
• 주석 생성하는 방법 : /** 입력 후 엔터시 아래와 같이 자동 생성.

/**
 *
 * @param paramMap
 * @param model
 * @return
 */

ControllerV4.

package hello.servlet.web.frontController.v4;

import java.util.Map;

public interface ControllerV4 {
    /**
     * @param paramMap
     * @param model
     * @return
     */
    String process(Map<String, String> paramMap, Map<String, Object> model);
}

MemberFormControllerV4.

package hello.servlet.web.frontController.v4.controller;

import hello.servlet.web.frontController.v4.ControllerV4;
import java.util.Map;

public class MemberFormControllerV4 implements ControllerV4 {

    @Override
    public String process(Map<String, String> paramMap, Map<String, Object> model) {
        return "new-form";
    }
}

MemberSaveControllerV4.

package hello.servlet.web.frontController.v4.controller;

import hello.servlet.domain.member.Member;
import hello.servlet.domain.member.MemberRepository;
import hello.servlet.web.frontController.ModelView;
import hello.servlet.web.frontController.v4.ControllerV4;

import java.util.Map;

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";
    }
}

MemberListControllerV4.

package hello.servlet.web.frontController.v4.controller;

import hello.servlet.domain.member.Member;
import hello.servlet.domain.member.MemberRepository;
import hello.servlet.web.frontController.ModelView;
import hello.servlet.web.frontController.v4.ControllerV4;

import java.util.List;
import java.util.Map;

public class MemberListControllerV4 implements ControllerV4 {

    private MemberRepository memberRepository = MemberRepository.getInstance();

    @Override
    public String process(Map<String, String> paramMap, Map<String, Object> model) {
        List<Member> members = memberRepository.findAll();
        model.put("members", members);
        return "members";
    }
}

FrontControllerServletV4.

package hello.servlet.web.frontController.v4;

import hello.servlet.web.frontController.ModelView;
import hello.servlet.web.frontController.MyView;
import hello.servlet.web.frontController.v4.ControllerV4;
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 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 = "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;
        }

        // paramMap
        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 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;
    }

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

모델 객체 전달

Map model = new HashMap<>(); // 추가

모델 객체를 프론트 컨트롤러에서 생성해서 넘겨준다.

컨트롤러에서 모델 객체에 값을 담으면 여기에 그대로 담기게 된다.

## 유연한 컨트롤러1_V5 (어댑터 패턴 사용)

ControllerV3 방식으로 or ControllerV4 방식 등 다양한 방식으로 개발하고 싶을때.. 

public interface ControllerV3 {

    ModelView process(Map<String, String> paramMap);
}

public interface ControllerV4 {
    /**
     * @param paramMap
     * @param model
     * @return
     */
    String process(Map<String, String> paramMap, Map<String, Object> model);
}

어댑터 패턴

• 어댑터 패턴을 사용, 프론트 컨트롤러가 다양한 방식의 컨트롤러를 처리할 수 있다.
• 핸들러 어댑터 : 핸들러를 처리해주는 어댑터. 여기서 어댑터 역할을 해줘서 다양한 컨트롤러 호출 가능하도록 함.
• 핸들러 : 컨트롤러. (컨트롤러의 이름을 넓은 범위인 핸들러로 변경, 어떤 종류라도 처리 가능하기 때문.)

MyHandlerAdapter.

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;
}

boolean supports(Object handler)

• handler는 컨트롤러를 의미. 어댑터가 해당 컨트롤러를 처리할 수 있는지 판단하는 메서드.

ModelView handle(HttpServletRequest request, HttpServletResponse response, Object handler)

• 어댑터는 실제 컨트롤러를 호출, 그 결과로 ModelView를 반환.
• 실제 컨트롤러가 ModelView를 반환하지 못하면, 어댑터가 ModelView를 직접 생성해서 반환. 

 ControllerV3HandlerAdapter.

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;
    }
}

FrontControllerServletV5.

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.v5.adapter.ControllerV3HandlerAdapter;

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> handelerMappingMap = new HashMap<>();
    private final List<MyHandlerAdapter> handlerAdapters = new ArrayList<>();

    public FrontControllerServletV5() {
        initHandlerMappingMap();    // 핸들러 매핑 초기화
        initHandlerAdapters();      // 어댑터 초기화
    }

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // handler 찾아오기.
        Object handler = getHandler(request);

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

        // handlerAdapt 찾아오기.
        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 void initHandlerMappingMap() {
        handelerMappingMap.put("/front-controller/v5/v3/members/new-form", new MemberFormControllerV3());
        handelerMappingMap.put("/front-controller/v5/v3/members/save", new MemberSaveControllerV3());
        handelerMappingMap.put("/front-controller/v5/v3/members", new MemberListControllerV3());
    }

    private void initHandlerAdapters() {
        handlerAdapters.add(new ControllerV3HandlerAdapter());
    }

    private Object getHandler(HttpServletRequest request) {
        String requestURI = request.getRequestURI();
        return handelerMappingMap.get(requestURI);
    }

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

## 유연한 컨트롤러2_V5

• 기존 FrontControllerServletV5 에 v3만 존재했는데, v4도 추가.

ControllerV4HandlerAdapter.

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);
        HashMap<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;
    }
}

## 정리.

1. V1 : 프론트 컨트롤러 도입. (기존 구조 유지, 프론트 컨트롤러 추가)
2. V2 : View 분류. (단순 반복되는 뷰 로직 분리)
3. V3 : Model 추가. (서블릿 종속성 제거, 뷰 이름 중복 제거)
4. V4 : 단순하고 실용적인 컨트롤러 (V3와 비슷, 구현 입장에서 modelView 직접 생성해서 반환하지 않도록 인터페이스 제공)
5. V5 : 유연한 컨트롤러 (어댑터 도입, 프레임워크를 유연하고 확장성 있게 설계)

• 스프링 MVC 핵심 구조를 파악하는데 필요한 부분 모두 들어있음. (스프링 MVC 프레임워크의 핵심 코드의 축약 버전, 구조 거의 동일)