[Web MVC] MVC 프레임워크 만들기

본 리뷰는 인프런 김영한님의 스프링 MVC 리뷰를 한 포스팅입니다.

 

목차

• 프론트 컨트롤러 패턴
• 프론트 컨트롤러 도입 - v1
• View 분리 -v2
• Model 추가 -v3
• 실용적인 컨트롤러 -v4
• 유연한 컨트롤러 -v5

 

1. 프론트 컨트롤러 패턴

프론트 컨트롤러 도입 전

클라이언트가 공통 로직이 필요하면 공통로직을 매번 호출해야하는 단점이 있었다.

프론트 컨트롤러 도입 전

 

프론트 컨트롤러 도입 후

공통의 관심사를 프론트 컨트롤러를 통해서 필요한 로직들을 호출할 수 있도록 만든다.

프론트 컨트롤러 서블릿 하나를 통해서 클라이언트의 요청을 모두 받고, 요청에 맞는 컨트롤러를 호출해준다.

따라서 서블릿 한개를 통해서 공통 처리 기능을 모두 수행하고, 나머지 컨트롤러는 서블릿을 별도로 사용하지 않아도 된다는 장점을 지닌다.

프론트 컨트롤러 도입 후

 

실제로, 스프링 웹 MVC의 핵심도 이러한 프론트 컨트롤러이다.

웹 MVC의 DispatcherServlet이 프론트 컨트롤러 패턴으로 구현되어 있다.

 

2. 프론트 컨트롤러 도입 - v1

v1

1) 클라이언트가 HTTP을 통해서 프론트 컨트롤러에 요청을 한다.

2) 프론트 컨트롤러는 매핑 정보를 통해서 컨트롤러를 조회해서 정보에 맞는 컨트롤러를 호출한다.

3) 컨트롤러에서 JSP forward를 통해서 JSP를 호출한다.

4) JSP를 통해서 HTML응답한다.

 

특징: 컨트롤러를 인터페이스로 만들 것이다!

 

컨트롤러 V1

 

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;

}

회원 등록 컨트롤러

 

package hello.servlet.web.frontcontroller.v1.controller;

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;

public class MemberFormControllerV1 implements ControllerV1 {

    @Override
    public void process(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String viewPath = "/WEB-INF/views/new-form.jsp";
        //서블릿에서 JSP호출
        RequestDispatcher dispatcher = request.getRequestDispatcher(viewPath);
        //다른 서블릿이나 JSP로 이동할 수 있는 기능이다.
        dispatcher.forward(request, response); //서버끼리 내부에서 호출
    }
}

회원 저장 컨트롤러

 

package hello.servlet.web.frontcontroller.v1.controller;

import hello.servlet.domain.member.Member;
import hello.servlet.domain.repository.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;

public class MemberSaveControllerV1 implements ControllerV1 {

    private MemberRepository memberRepository = MemberRepository.getInstance();

    @Override
    public void 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);

        //Model 데이터 보관
        request.setAttribute("member", member);

        String viewPath = "/WEB-INF/views/save-result.jsp";
        RequestDispatcher dispatcher = request.getRequestDispatcher(viewPath);
        dispatcher.forward(request, response);
    }
}

회원 목록 컨트롤러

 

package hello.servlet.web.frontcontroller.v1.controller;

import hello.servlet.domain.member.Member;
import hello.servlet.domain.repository.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);
    }
}

프론트 컨트롤러

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 {

    //매핑정보
    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");

        //다형성을 이용
        String requestURI = request.getRequestURI();
        ControllerV1 controllerV1 = controllerMap.get(requestURI);

        //예외처리
        if(controllerV1 == null){
            response.setStatus(HttpServletResponse.SC_NOT_FOUND);
            return;
        }

        controllerV1.process(request, response);

    }
}

 

 

3. View 분리 - v2

 String viewPath = "/WEB-INF/views/new-form.jsp";
RequestDispatcher dispatcher = request.getRequestDispatcher(viewPath);
dispatcher.forward(request, response);

처럼 반복되고 중복적인 코드가 있기에 깔금하지 않다.

그래서 우리는 별도로 뷰를 처리하는 객체를 만들 예정이다.

v2

 

1) HTTP요청

2) 프론트 컨트롤러에서 매핑정보를 이용하여 컨트롤러를 조회한 후 호출한다.

3) 컨트롤러에서 MyView 객체를 이용하여 반환한다.

4) 프론트 컨트롤러에서 렌더링하여 MyView객체로 전송한 후 MyView에서 JSP로 포워드한다.

5) JSP를 통해서 HTML응답한다.

 

 

 

컨트롤러V2

package hello.servlet.web.frontcontroller.v2;

import hello.servlet.web.frontcontroller.MyView;

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

public interface ControllerV2 {

    //return MyView 객체
    MyView process(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException;

}

 

View객체

package hello.servlet.web.frontcontroller;

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

 

 

회원등록 컨트롤러

package hello.servlet.web.frontcontroller.v2.controller;

import hello.servlet.web.frontcontroller.MyView;
import hello.servlet.web.frontcontroller.v2.ControllerV2;

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

public class MemberFormControllerV2 implements ControllerV2 {

    @Override
    public MyView process(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        return new MyView("/WEB-INF/views/new-form.jsp");
    }
}

 

 

회원저장 컨트롤러

package hello.servlet.web.frontcontroller.v2.controller;

import hello.servlet.domain.member.Member;
import hello.servlet.domain.repository.MemberRepository;
import hello.servlet.web.frontcontroller.MyView;
import hello.servlet.web.frontcontroller.v2.ControllerV2;

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

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);

        //Model 데이터 보관
        request.setAttribute("member", member);

        return new MyView("/WEB-INF/views/save-result.jsp");
    }
}

 

회원목록 컨트롤러

package hello.servlet.web.frontcontroller.v2.controller;

import hello.servlet.domain.member.Member;
import hello.servlet.domain.repository.MemberRepository;
import hello.servlet.web.frontcontroller.MyView;
import hello.servlet.web.frontcontroller.v2.ControllerV2;

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 MemberListControllerV2 implements ControllerV2 {

    private MemberRepository memberRepository = MemberRepository.getInstance();

    @Override
    public MyView process(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        List<Member> members = memberRepository.findAll();
        request.setAttribute("members", members);

        return new MyView("/WEB-INF/views/members.jsp");
    }
}

 

프론트 컨트롤러

package hello.servlet.web.frontcontroller.v2;

import hello.servlet.web.frontcontroller.MyView;
import hello.servlet.web.frontcontroller.v1.ControllerV1;
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 hello.servlet.web.frontcontroller.v2.controller.MemberFormControllerV2;
import hello.servlet.web.frontcontroller.v2.controller.MemberListControllerV2;
import hello.servlet.web.frontcontroller.v2.controller.MemberSaveControllerV2;

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 = "frontControllerServletV2", urlPatterns = "/front-controller/v2/*")
public class FrontControllerServletV2 extends HttpServlet {

    //매핑정보
    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 {

        //다형성을 이용
        String requestURI = request.getRequestURI();
        ControllerV2 controllerV2 = controllerMap.get(requestURI);

        //예외처리
        if(controllerV2 == null){
            response.setStatus(HttpServletResponse.SC_NOT_FOUND);
            return;
        }

        MyView view = controllerV2.process(request, response);
        view.render(request, response);

    }
}

 

ControllerV2의 반환타입이 view객체인 Myview이므로 프론트 컨트롤러는 컨트롤러의 호출 결과로 Myview를 받는다.

그리고 view.render를 호출하면 forward로직을 수행해서 JSP가 실행되고, HTML을 통하여 응답을 받습니다.

 

 

 

4. Model 추가 -v3

HttpServlet의 종속성을 제거하고 뷰 이름 중복을 제거하면서 더욱 심플하고 테스트 코드를 작성하기 쉬운 코드로 변경할 예정입니다.

서블릿 종속성을 제거함으로, HttpServletRequest, HttpServletResponse가 필요없어집니다.

 

뷰 이름 중복을 제거함으로,

 

/WEB-INF/views/new-form.jsp👉 new-form

/WEB-INF/views/save-result.jsp👉 save-result

/WEB-INF/views/members.jsp👉 members

을 통하여 향후 뷰의 폴더 위치와 함께 이동해도 프론트 컨트롤러의 로직만 변경하면 됨으로 유지보수가 수월한 장점을 지니고 있습니다.

 

v3

 

1) 클라이언트가 프론트 컨트롤러에 HTTP요청

2) 프론트 컨트롤러는 매핑정보를 통하여 알맞은 컨트롤러를 호출

3) 컨트롤러는 프론트컨트롤러에게 model과 view가 섞여있는 ModelView 반환

4) 프론트 컨트롤러는 viewResolver(논리 -> 물리)를 통하여 MyView 객체 반환

5) 반환받은 객체 랜더링 호출 (model)

6) Myview객체를 통하여 HTML응답

 

 

ModelView

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;
    }
}

 

MyView

package hello.servlet.web.frontcontroller;

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.Map;

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 static void modelToRequestAttribute(Map<String, Object> model, HttpServletRequest request) {
        model.forEach((key, value) -> request.setAttribute(key, value));
    }
}

 

ControllerV3

package hello.servlet.web.frontcontroller.v3;

import hello.servlet.web.frontcontroller.ModelView;

import java.util.Map;

public interface ControllerV3 {

    //서블릿 종속성 제거
    ModelView process(Map<String, String> paramMap);

}

 

회원 등록 컨트롤러

package hello.servlet.web.frontcontroller.v3.controller;

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

import java.util.Map;

public class MemberFormControllerV3 implements ControllerV3 {

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

 

회원 저장 컨트롤러

package hello.servlet.web.frontcontroller.v3.controller;

import hello.servlet.domain.member.Member;
import hello.servlet.domain.repository.MemberRepository;
import hello.servlet.web.frontcontroller.ModelView;
import hello.servlet.web.frontcontroller.v3.ControllerV3;
import org.springframework.ui.Model;

import java.util.Map;

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;
    }
}

 

회원 목록 컨트롤러

package hello.servlet.web.frontcontroller.v3.controller;

import hello.servlet.domain.member.Member;
import hello.servlet.domain.repository.MemberRepository;
import hello.servlet.web.frontcontroller.ModelView;
import hello.servlet.web.frontcontroller.v3.ControllerV3;

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

public class MemberListControllerV3 implements ControllerV3 {
    private MemberRepository memberRepository = MemberRepository.getInstance();

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

 

프론트 컨트롤러

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.MemberFormControllerV3;
import hello.servlet.web.frontcontroller.v3.controller.MemberListControllerV3;
import hello.servlet.web.frontcontroller.v3.controller.MemberSaveControllerV3;

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 = "frontControllerServletV3", urlPatterns = "/front-controller/v3/*")
public class FrontControllerServletV3 extends HttpServlet {

    //매핑정보
    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 {

        //다형성을 이용
        String requestURI = request.getRequestURI();
        ControllerV3 controllerV3 = controllerMap.get(requestURI);

        //예외처리
        if(controllerV3 == null){
            response.setStatus(HttpServletResponse.SC_NOT_FOUND);
            return;
        }

        //paramMap
        Map<String, String> paramMap = createParamMap(request);
        ModelView mv = controllerV3.process(paramMap);

        MyView myView = viewResolver(mv);
        myView.render(mv.getModel(), request, response);
    }

    private static MyView viewResolver(ModelView mv) {
        return new MyView("/WEB-INF/views/" + mv.getViewName() + ".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;
    }
}

 

5. 실용적인 컨트롤러 -v4

v3를 조금 변경하여 개발자들이 매우 편리하게 개발할 수 있는 v4버전을 개발해보자.

ModelView반환하는 것이 아닌 ViewName을 반환하도록 변경

 

 

ControllerV4

package hello.servlet.web.frontcontroller.v4;

import java.util.Map;

public interface ControllerV4 {
    /**
     * @param paramMap
     * @param model
     * @return viewName
     */

    String process(Map<String, String> paramMap, Map<String, Object> model);

}

 

회원 가입 컨트롤러

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";
    }
}

 

회원 저장 컨트롤러

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

import hello.servlet.domain.member.Member;
import hello.servlet.domain.repository.MemberRepository;
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";
    }
}

 

회원 목록 컨트롤러

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

import hello.servlet.domain.member.Member;
import hello.servlet.domain.repository.MemberRepository;
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";
    }
}

 

프론트 컨트롤러

package hello.servlet.web.frontcontroller.v4;

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 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 {

    //매핑정보
    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 {

        //다형성을 이용
        String requestURI = request.getRequestURI();
        ControllerV4 controllerV4 = controllerMap.get(requestURI);

        //예외처리
        if(controllerV4 == null){
            response.setStatus(HttpServletResponse.SC_NOT_FOUND);
            return;
        }

        //paramMap
        Map<String, String> paramMap = createParamMap(request);
        //model
        Map<String, Object> model = new HashMap<>();
        String viewName = controllerV4.process(paramMap, model);

        MyView myView = viewResolver(viewName);
        myView.render(model, 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;
    }
}

 

   -. 이번 버전은 매우 단순하고 실용적이다.

   -. v3에서 모델을 파라미터로 넘기고 뷰의 놀리이름을 반환한다는 아이디어 적용 완료

   -. 처음부터 한번에 온 것이 아닌 프레임워크가 점진적으로 발전하는 과정 속에서 나온 결과물 !

 

 

6. 유연한 컨트롤러 -v5 to v3

지금까지 만들었던 버전들은 각자의 버전에 맞도록 설정을 해두어야했었는데 이번 버전은 사용자가 직접 버전을 선택하여 프레임워크 개발을 진행할 수 있도록 만든 버전입니다.

이 버전에서는 어뎁터 패턴을 사용해서 프론트 컨트롤러가 다양한 방식의 컨트롤러를 처리할 수 있도록 변경해볼 예정입니다.

 

구조

앞서 v4의 구조를 활용하되, 핸들러 어뎁터와 핸들러를 이용합니다.

핸들러 어댑터: 중간에 어댑터 역할을 하는 어댑터가 추가되었는데 이름이 핸들러 어댑터이다. 여기서 어댑터 역할을 해주는 덕분에 다양한 종류의 컨트롤러를 호출할 수 있다.
핸들러: 컨트롤러의 이름을 더 넓은 범위인 핸들러로 변경했다. 그 이유는 이제 어댑터가 있기 때문에 꼭 컨트롤러의 개념 뿐만 아니라 어떠한 것이든 해당하는 종류의 어댑터만 있으면 다 처리할 수 있기 때문이다.

 

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 {

    //핸들러 지원가능 여부 판단
    boolean supports(Object handler);

    ModelView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws ServletException, IOException;

}

 

 

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.v3.FrontControllerServletV3;
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) {
        // ControllerV3를 구현할 수 있는 instance가 오면 참을 반환, 아니라면 거짓 반환
        return (handler instanceof ControllerV3);
    }

    @Override
    public ModelView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws ServletException, IOException {
        //ControllerV3를 구현할 수 있기때문에 타입케스팅해도된다.
        ControllerV3 controller = (ControllerV3) handler;

        Map<String, String> paramMap = createParamMap(request);
        return controller.process(paramMap);
    }

    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;
    }
}

 

프론트 컨트롤러

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 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 {

    //기존
//    private Map<String, ControllerV4> controllerMap = new HashMap<>();

    //변경 후 (Object타입 이용)
    private final Map<String, Object> handlerMappingMap = new HashMap<>();
    private final List<MyHandlerAdapter> handlerAdapters = new ArrayList<>();

    public FrontControllerServletV5() {
        initHandlerMappingMap();

        initHandlerAdapters();
    }

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

    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());
    }

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //다형성을 이용
        Object handler = getHandler(request);

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

 

6. 유연한 컨트롤러 -v5 to v4

 v4 handlerAdapter

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 {
        //ControllerV4를 구현할 수 있기때문에 타입케스팅해도된다.
        ControllerV4 controller = (ControllerV4) handler;

        Map<String, String> paramMap = createParamMap(request);
        HashMap<String, Object> model = new HashMap<>();

        String viewName = controller.process(paramMap, model);

        ModelView modelView = new ModelView(viewName);
        modelView.setModel(model);

        return modelView;
    }

    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;
    }
}

프론트 컨트롤러 추가 (V4)

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.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 {

    //기존
//    private Map<String, ControllerV4> controllerMap = new HashMap<>();

    //변경 후 (Object타입 이용)
    private final Map<String, Object> handlerMappingMap = new HashMap<>();
    private final List<MyHandlerAdapter> handlerAdapters = new ArrayList<>();

    public FrontControllerServletV5() {
        initHandlerMappingMap();

        initHandlerAdapters();
    }

    private void initHandlerAdapters() {
        handlerAdapters.add(new ControllerV3HandlerAdapter());
        handlerAdapters.add(new ControllerV4HandlerAdapter());
    }

    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());

        //V4 추가
        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());
    }

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //다형성을 이용
        //MemberFormControllerV3
        Object handler = getHandler(request);

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

        //ControllerV3HandlerAdapter
        MyHandlerAdapter adapter = getHandlerAdapter(handler);
        ModelView mv = adapter.handle(request, response, handler);

        String viewName = mv.getViewName();
        MyView myView = viewResolver(viewName);
        myView.render(mv.getModel(), request, response);
    }

    private MyHandlerAdapter getHandlerAdapter(Object handler) {
        //MemberFormControllerV3
        for (MyHandlerAdapter adapter : handlerAdapters) {
            // True -> ControllerV3HandlerAdapter
            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 static MyView viewResolver(String viewName) {
        return new MyView("/WEB-INF/views/" + viewName + ".jsp");
    }
}