[Java][Spring] 프론트 컨트롤러 패턴 -V1

프론트 컨트롤러 패턴

프론트 컨트롤러 도입 전

프론트 컨트롤러 도입 후

V1 구조

 

FrontController 패턴 특징

• 컨트롤러 서블릿 하나로 클라이언트 요청 처리(프론트 컨트롤러가 요청에 맞는 컨트롤러를 찾아서 호출)
• 입구가 하나 (공통 처리가 가능)
• 나머지 컨트롤러는 서블릿을 사용하지 않아도 된다. (중복 제거)

ControllerV1

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;

}

• servlet과 비슷한 컨트롤러 인터페이스 구현
• 다형성을 활용해 여러 인터페이스를 구현하기 위해서
  • 사용자 입력 기능(form), 저장 기능(save), 조회 기능(list)

MemberFormControllerV1

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

import hello.servlet.web.frontcontroller.v1.ControllerV1;
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 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 jakarta.servlet.RequestDispatcher;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.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 저장
        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 jakarta.servlet.RequestDispatcher;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.util.List;

public class MemberListController 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);
    }
}

FrontControllerServlet

package hello.servlet.web.frontcontroller.v1;

import hello.servlet.web.frontcontroller.v1.controller.MemberFormControllerV1;
import hello.servlet.web.frontcontroller.v1.controller.MemberListController;
import hello.servlet.web.frontcontroller.v1.controller.MemberSaveControllerV1;
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> 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 MemberListController());
    }

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        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 포함한 하위 모든 요청은 이 서블릿에서 받아들인다.

controllerMap

• key: 매핑 URL
• value: 호출될 컨트롤러

service()

• requestURI 를 조회해서 실제 호출할 컨트롤러를 controllerMap 에서 찾는다.
• 만약 없다면 404(SC_NOT_FOUND) 상태 코드를 반환(예외 처리)
• 컨트롤러를 찾고 controller.process(request, response); 을 호출해서 해당 컨트롤러를 실행한다.

JSP
JSP는 이전 MVC에서 사용했던 것을 그대로 사용한다.