[MVC] 프론트 컨트롤러 패턴

V1 구조

public class MemberControllerV1 implements ControllerV1 {
	@Override
    public void process(HttpServletRequest request, HttpServletResponseresponse) throws ServletException, IOException {
		String viewPath = "/WEB-INF/views/new-form.jsp";
		RequestDispatcher dispatcher = request.getRequestDispatcher(viewPath);
		dispatcher.forward(request, response);
	}
}

@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/members", new MemberControllerV1());
 	}
 
 	@Override
 	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 		System.out.println("FrontControllerServletV1.service");
		String requestURI = request.getRequestURI();
 		ControllerV1 controller = controllerMap.get(requestURI);
 		if (controller == null) {
 			response.setStatus(HttpServletResponse.SC_NOT_FOUND);
 			return;
 		}
 		controller.process(request, response);
 	}
}

 

 

V2 구조

• View 분리
• process에서 render로 분리 후 dispatcher에서 render로 실행

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 class MemberFormControllerV2 implements ControllerV2 {
	@Override
	public MyView process(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		return new MyView("/WEB-INF/views/new-form.jsp");
	}
}

public class FrontControllerServletV2 extends HttpServlet {

	@Override
	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 		MyView view = controller.process(request, response);
 		view.render(request, response);
 	}
}

 

 

 

V3 구조

• 서블릿 종속성 제거 : HttpServletRequest, HttpServletResponse
• 뷰 이름 중복 제거 : /WEB-INF/views/new-form.jsp => new-form

public class MyView {
	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));
 	}
}

public class ModelView {
	private String viewName;
	private Map<String, Object> model = new HashMap<>();
	
    public ModelView(String viewName) {
		this.viewName = viewName;
	}
}


public class MemberControllerV3 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;
 	}
}


public class FrontControllerServletV3 extends HttpServlet {
	
 	@Override
 	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Map<String, String> paramMap = createParamMap(request);
 		ModelView mv = controller.process(paramMap);
 		
        String viewName = mv.getViewName();
 		MyView view = viewResolver(viewName);
 		view.render(mv.getModel(), 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");
 	}   
}

 

 

 

V4 구조

• ModelView 반환 => ViewName만 반환
• Model을 MemberController 내부에서 생성 후 반환하는 것이 아닌
• FrontController에서 생성한 Model을 넘겨서 Controller에서 값을 대입해주며 Model을 분리함으로써
• ViewName만을 반환할 수 있게 됌

public class MemberControllerV4 implements ControllerV4 {
	@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";	
	}
}

public class FrontControllerServletV4 extends HttpServlet {
	@Override
	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		Map<String, String> paramMap = createParamMap(request);
		Map<String, Object> model = new HashMap<>(); //추가
	
    	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");
 	}
}

 

 

 

V5 구조

public interface MyHandlerAdapter {
	boolean supports(Object handler);
	ModelView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws ServletException, IOException;
}

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) {
		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;
	}
}

public class FrontControllerServletV5 extends HttpServlet {
	private final Map<String, Object> handlerMappingMap = new HashMap<>();
	private final List<MyHandlerAdapter> handlerAdapters = new ArrayList<>();
	public FrontControllerServletV5() {
 		initHandlerMappingMap();
 		initHandlerAdapters();
 	}
 	
    private void initHandlerMappingMap() {
 		handlerMappingMap.put("/front-controller/v5/v3/members/new-form", new MemberFormControllerV3());
	}
 	private void initHandlerAdapters() {
 		handlerAdapters.add(new ControllerV3HandlerAdapter());
 	}
 
 	@Override
 	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		MyHandlerAdapter adapter = getHandlerAdapter(handler);
		ModelView mv = adapter.handle(request, response, handler);
		
        MyView view = viewResolver(mv.getViewName());
		view.render(mv.getModel(), request, response);
	}
 
	private Object getHandler(HttpServletRequest request) {
		String requestURI = request.getRequestURI();
 		return handlerMappingMap.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");
 	}
}