스프링 16일차

인프런 김영한 님의 강의를 참고했습니다.

스프링 MVC 1편 - 백엔드 웹 개발 핵심 기술 - 인프런 | 강의

 

저번에 만들었던 서블릿에 컨트롤러를 추가해보자.

 

현재 만들어둔 컨트롤러는 공통된 부분이 많고 하는 일도 비슷하다.

그럴 때는 FrontController를 생성해준다.

이 FrontController가 요청을 받고 그 요청에 맞는 컨트롤러를 호출해주는 역할을 한다.

 

우선 프론트 컨트롤러 자체를 도입해보자.

우선 다형성을 이용해 컨트롤러 인터페이스를 만들어보자.

package hello.servlet.web.frontcontroller.version1;

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;
}

이렇게 만들고 각 컨트롤러들이 이 인터페이스를 구현하게 해주면 요청에 따른 컨트롤러는 모두 준비가 된다.

 

이제 FrontController를 만들어준다.

package hello.servlet.web.frontcontroller.version1;

import hello.servlet.web.frontcontroller.version1.controller.StudentFormControllerV1;
import hello.servlet.web.frontcontroller.version1.controller.StudentListControllerV1;
import hello.servlet.web.frontcontroller.version1.controller.StudentSaveControllerV1;
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> controllerMap = new HashMap<>();
    
    public FrontControllerServletV1(){
        controllerMap.put("/front-controller/v1/students/new-form", new StudentFormControllerV1());
        controllerMap.put("/front-controller/v1/students/save", new StudentSaveControllerV1());
        controllerMap.put("/front-controller/v1/students", new StudentListControllerV1());
    }

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ControllerV1 controller = controllerMap.get(req.getRequestURI());
        if(controller == null){
            resp.setStatus(HttpServletResponse.SC_NOT_FOUND);
            return;
        }
        
        controller.process(req, resp);
    }
}

이렇게 Map에 컨트롤러들을 담아준 후 URI를 확인하여 거기에 맞는 컨트롤러로 보내준다.

 

이제 계속 리팩토링을 진행해보자.

모든 컨트롤러에서 중복되는 부분이 있다.

이 부분을 모아주어야 깔끔하고, 후에 수정하기도 쉽다.

이런 상태에서 중간에 MyView를 추가하여 dispatcher.forward()를 맡길 예정이다.

package hello.servlet.web.frontcontroller;

import jakarta.servlet.RequestDispatcher;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.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 requestDispatcher = request.getRequestDispatcher(viewPath);
        requestDispatcher.forward(request, response);
    }
}

이렇게 생성자로 viewPath를 입력받아서 render를 이용하여 jsp로 넘겨준다.

 

나머지 코드들은 저 부분을 빼서 다시 작성한다고 생각하면 된다.

package hello.servlet.web.frontcontroller.version2;

import hello.servlet.web.frontcontroller.MyView;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;

public interface ControllerV2 {

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

package hello.servlet.web.frontcontroller.version2.controller;

import hello.servlet.web.frontcontroller.MyView;
import hello.servlet.web.frontcontroller.version2.ControllerV2;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;

public class StudentFormControllerV2 implements ControllerV2 {

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

package hello.servlet.web.frontcontroller.version2.controller;

import hello.servlet.domain.student.Student;
import hello.servlet.domain.student.StudentRepository;
import hello.servlet.web.frontcontroller.MyView;
import hello.servlet.web.frontcontroller.version2.ControllerV2;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;

public class StudentSaveControllerV2 implements ControllerV2 {

    private StudentRepository studentRepository = StudentRepository.getInstance();

    @Override
    public MyView process(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String studentName = request.getParameter("studentName");
        int year = Integer.parseInt(request.getParameter("year"));

        Student student = new Student(studentName, year);
        studentRepository.save(student);

        request.setAttribute("student", student);

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

package hello.servlet.web.frontcontroller.version2.controller;

import hello.servlet.domain.student.Student;
import hello.servlet.domain.student.StudentRepository;
import hello.servlet.web.frontcontroller.MyView;
import hello.servlet.web.frontcontroller.version2.ControllerV2;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

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

public class StudentListControllerV2 implements ControllerV2 {

    private StudentRepository studentRepository = StudentRepository.getInstance();

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

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

그러고 FrontController는 이렇게 작성을 해준다.

package hello.servlet.web.frontcontroller.version2;

import hello.servlet.web.frontcontroller.MyView;
import hello.servlet.web.frontcontroller.version2.controller.StudentFormControllerV2;
import hello.servlet.web.frontcontroller.version2.controller.StudentListControllerV2;
import hello.servlet.web.frontcontroller.version2.controller.StudentSaveControllerV2;
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 = "frontControllerServletV2", urlPatterns = "/front-controller/v2/*")
public class FrontControllerServletV2 extends HttpServlet {

    private Map<String, ControllerV2> controllerMap = new HashMap<>();

    public FrontControllerServletV2(){
        controllerMap.put("/front-controller/v1/students/new-form", new StudentFormControllerV2());
        controllerMap.put("/front-controller/v1/students/save", new StudentSaveControllerV2());
        controllerMap.put("/front-controller/v1/students", new StudentListControllerV2());
    }

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ControllerV2 controller = controllerMap.get(req.getRequestURI());
        if(controller == null){
            resp.setStatus(HttpServletResponse.SC_NOT_FOUND);
            return;
        }

        MyView view = controller.process(req, resp);
        view.render(req, resp);
    }
}

request와 response에 데이터를 받고 view로 경로를 받은 후에 실행해주는 것이다.

 

다음 리펙토링이다.

컨트롤러에서는 request와 response가 꼭 필요하지 않다.

어차피 데이터를 넘길거면 담아서 넘기는 게 아니라 그냥 넘기면 되기 때문이다.

그렇기 때문에 컨트롤러에서 서블릿 기술을 제외해보자.

 

스프링처럼 Model을 만들어 데이터를 넘기도록 한다.

이렇게 Controller에서 Model에 데이터만 담아서 가져오는 것이다.

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, Map<String, Object> model) {
        this.viewName = viewName;
    }
}

이렇게 Map으로 key, value로 데이터들을 저장하도록 만든다.

그러고 경로를 저장하기 위해서 viewName을 사용한다.

 

이제 ModelView를 리턴하도록 코드들을 바꾸어보자.

package hello.servlet.web.frontcontroller.version3;

import hello.servlet.web.frontcontroller.ModelView;

import java.util.Map;

public class StudentFormControllerV3 implements ControllerV3{

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

이렇게 Model에 jsp의 경로와 데이터들을 넣어준다.

package hello.servlet.web.frontcontroller.version3;

import hello.servlet.domain.student.Student;
import hello.servlet.domain.student.StudentRepository;
import hello.servlet.web.frontcontroller.ModelView;

import java.util.Map;

public class StudentSaveControllerV3 implements ControllerV3{
    
    private StudentRepository studentRepository = StudentRepository.getInstance();

    @Override
    public ModelView process(Map<String, String> paramMap) {
        String studentName = paramMap.get("studentName");
        int year = Integer.parseInt(paramMap.get("year"));
        
        Student student = new Student(studentName, year);
        studentRepository.save(student);
        
        ModelView modelView = new ModelView("save-result");
        modelView.getModel().put("student", student);
        return modelView;
    }
}

package hello.servlet.web.frontcontroller.version3;

import hello.servlet.domain.student.Student;
import hello.servlet.domain.student.StudentRepository;
import hello.servlet.web.frontcontroller.ModelView;

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

public class StudentListControllerV3 implements ControllerV3{

    private StudentRepository studentRepository = StudentRepository.getInstance();

    @Override
    public ModelView process(Map<String, String> paramMap) {
        List<Student> students = studentRepository.findAll();

        ModelView modelView = new ModelView("students");
        modelView.getModel().put("students", students);
        
        return modelView;
    }
}

 

이제 이렇게 작동할 FrontController를 작성한다.

package hello.servlet.web.frontcontroller.version2;

import hello.servlet.web.frontcontroller.ModelView;
import hello.servlet.web.frontcontroller.MyView;
import hello.servlet.web.frontcontroller.version2.controller.StudentFormControllerV2;
import hello.servlet.web.frontcontroller.version2.controller.StudentListControllerV2;
import hello.servlet.web.frontcontroller.version2.controller.StudentSaveControllerV2;
import hello.servlet.web.frontcontroller.version3.ControllerV3;
import hello.servlet.web.frontcontroller.version3.StudentFormControllerV3;
import hello.servlet.web.frontcontroller.version3.StudentListControllerV3;
import hello.servlet.web.frontcontroller.version3.StudentSaveControllerV3;
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 = "frontControllerServletV3", urlPatterns = "/front-controller/v3/*")
public class FrontControllerServletV3 extends HttpServlet {

    private Map<String, ControllerV3> controllerMap = new HashMap<>();

    public FrontControllerServletV3(){
        controllerMap.put("/front-controller/v3/students/new-form", new StudentFormControllerV3());
        controllerMap.put("/front-controller/v3/students/save", new StudentSaveControllerV3());
        controllerMap.put("/front-controller/v3/students", new StudentListControllerV3());
    }

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ControllerV3 controller = controllerMap.get(req.getRequestURI());
        if(controller == null){
            resp.setStatus(HttpServletResponse.SC_NOT_FOUND);
            return;
        }

        Map<String, String> paramMap = createParamMap(req);
        ModelView modelView = controller.process(paramMap);

        String viewName = modelView.getViewName();
        MyView view = viewer(viewName);
        view.render(modelView.getModel(), req, resp);
    }

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

    private Map<String, String> createParamMap(HttpServletRequest req) {
        Map<String, String> paramMap = new HashMap<>();
        req.getParameterNames().asIterator()
                .forEachRemaining(paramName -> paramMap.put(paramName, req.getParameter(paramName)));

        return paramMap;
    }
}

여기에 MyView에 파라미터가 3개 들어가는 생성자가 호출 되었으니, 그에 맞게 생성자를 추가해준다.