스프링 MVC 5일차_MVC 프레임워크 만들기_1

# MVC 프레임워크 만들기_1

## 프론트 컨트롤러 패턴 

• 프론트 컨트롤러 도입 전 : 공통 로직 없이, 각각의 요청에 마다 각각 생성하여 처리.
• 프론트 컨트롤러 도입 후 : 프론트 컨트롤러에 공통 로직을 두고, 요청에 따른 응답 처리.

프론트 컨트롤러 특징.

• 프론트 컨트롤러 서블릿 하나로 클라이언트의 요청을 받음
• 프론트 컨트롤러가 요청에 맞는 컨트롤러를 찾아서 호출 (입구가 하나)
• 공통 처리 가능
• 프론트 컨트롤러를 제외한 나머지 컨트롤러는 서블릿을 사용하지 않아도 됨 (프론트 컨트롤러에서 직접 호출)

스프링 웹 MVC와 프론트 컨트롤러

• 스프링 웹 MVC의 핵심도 FrontController
• 스프링 웹 MVC의 DispatcherServlet 이 FrontController 패턴으로 구현되어 있음

## 프론트 컨트롤러 도입_V1

• 프론트 컨트롤러를 단계적으로 도입.
• 기존 코드를 최대한 유지하면서, 프론트 컨트롤러를 도입.

ControllerV1 (인터페이스)

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;
}

• 서블릿과 비슷한 모양의 컨트롤러 인터페이스 도입.
• 각 컨트롤러들은 해당 인터페이스를 구현.
• 프론트 컨트롤러는 해당 인터페이스를 호출해서 구현과 관계없이 로직의 일관성을 가져갈 수 있다. 
• V1은 기존 로직을 최대한 유지하는게 핵심.

MemberFormControllerV1

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";
        RequestDispatcher dispatcher = request.getRequestDispatcher(viewPath);
        dispatcher.forward(request, response);
    }
}

MemberSaveControllerV1

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;

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);

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

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

MemberListControllerV1

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);
    }
}

FrontControllerServletV1

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

• urlPatterns = "/front-controller/v1/*" : /front-controller/v1 를 포함한 하위 모든 요청은 해당 서블릿에서 받아들임. 

controllerMap

• key : 매핑 URL
• value : 호출될 컨트롤러

정리.

• 클라이언트가 HTTP 요청 > 프론트 컨트롤러에서 요청을 받고, 매핑정보 조회 > 조회한 컨트롤러 호출 > JSP forward > HTML 응답.

## View 분리_V2

• 모든 컨트롤러에서 뷰로 이동하는 부분에 중복 존재.

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

• 해당 부분을 분리하기 위해 뷰를 처리하는 객체 생성.

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;

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);
    }
}

ControllerV2.

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 {

    MyView process(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException;
}

MemberFormControllerV2.

package hello.servlet.web.frontController.v2;

import hello.servlet.web.frontController.MyView;

import javax.servlet.RequestDispatcher;
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");
    }
}

MemberSaveControllerV2.

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

import hello.servlet.domain.member.Member;
import hello.servlet.domain.member.MemberRepository;
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 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);

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

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

MemberListControllerV2.

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

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

FrontControllerServletV2.

package hello.servlet.web.frontController.v2;

import hello.servlet.web.frontController.MyView;
import hello.servlet.web.frontController.v2.ControllerV2;
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 {

    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);
    }
}

• 프론트 컨트롤러의 도입으로 MyView 객체의 render() 를 호출하는 부분을 모두 일관되게 처리.
• 각각의 컨트롤러는 MyView 객체를 생성만 해서 반환하면 된다.

## Model 추가_V3

• 요청 파라미터 정보는 자바의 Map으로 대신 넘기도록 하여 지금 구조에서 컨트롤러가 서블릿 기술을 몰라도 동작하도록 함.
• request 객체를 Model로 사용하는 대신 별도의 Model 객체를 만들어서 반환.
• 이름 중복 제거, 컨트롤러는 뷰의 논리 이름을 반환하고, 실제 물리 위치의 이름은 프론트 컨트롤러에서 처리하도록 단순화.

ModelView.

package hello.servlet.web.frontController;

import java.util.HashMap;
import java.util.Map;

public class ModelView {

    private String viewName;
    private Map<String, Object> model = new HashMap<>();

    public ModelView(String viewName) {
        this.viewName = viewName;
    }

    public String getViewName() {
        return viewName;
    }

    public void setViewName(String viewName) {
        this.viewName = viewName;
    }

    public Map<String, Object> getModel() {
        return model;
    }

    public void setModel(Map<String, Object> model) {
        this.model = model;
    }
}

 ControllerV3.

package hello.servlet.web.frontController.v3;

import hello.servlet.web.frontController.ModelView;

import java.util.Map;

public interface ControllerV3 {

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

MemberFormControllerV3.

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");
    }
}

MemberSaveControllerV3.

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

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

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;
    }
}

MemberListControllerV3.

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

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

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

뷰 리졸버

• MyView view = viewResolver(viewName) 컨트롤러가 반환한 논리 뷰 이름을 실제 물리 뷰 경로로 변경.
• 실제 물리 경로가 있는 MyView 객체를 반환. (논리 뷰 이름 : members / 물리 뷰 경로 : /WEB-INF/views/members.jsp)