인프런 커뮤니티 질문&답변

학습하는 분들께 도움이 되고, 더 좋은 답변을 드릴 수 있도록 질문전에 다음을 꼭 확인해주세요.

1. 강의 내용과 관련된 질문을 남겨주세요.
2. 인프런의 질문 게시판과 자주 하는 질문(링크)을 먼저 확인해주세요.
(자주 하는 질문 링크: https://bit.ly/3fX6ygx)
3. 질문 잘하기 메뉴얼(링크)을 먼저 읽어주세요.
(질문 잘하기 메뉴얼 링크: https://bit.ly/2UfeqCG)

질문 시에는 위 내용은 삭제하고 다음 내용을 남겨주세요.
=========================================
[질문 템플릿]
1. 강의 내용과 관련된 질문인가요? (예/아니오)
2. 인프런의 질문 게시판과 자주 하는 질문에 없는 내용인가요? (예/아니오)
3. 질문 잘하기 메뉴얼을 읽어보셨나요? (예/아니오)

[질문 내용]

java.lang.NullPointerException: Cannot invoke "hello.servlet.web.frontcontroller.ModelView.getViewName()" because "mv" is null

at hello.servlet.web.frontcontroller.v5.FrontControllerServletV5.service(FrontControllerServletV5.java:57) ~[classes/:na]

at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:614) ~[jakarta.servlet-api-6.0.0.jar:6.0.0]

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:205) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) ~[tomcat-embed-websocket-10.1.16.jar:10.1.16]

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-6.1.1.jar:6.1.1]

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.1.jar:6.1.1]

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-6.1.1.jar:6.1.1]

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.1.jar:6.1.1]

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-6.1.1.jar:6.1.1]

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.1.jar:6.1.1]

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:482) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:340) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:391) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:896) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1744) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-10.1.16.jar:10.1.16]

at java.base/java.lang.Thread.run(Thread.java:833) ~[na:na]

---

package hello.servlet.web.frontcontroller.v5;

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

    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());
        handlerMappingMap.put("/front-controller/v5/v3/members/save", new MemberSaveControllerV3());
        handlerMappingMap.put("/front-controller/v5/v3/members", new MemberListControllerV3());
    }

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

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        Object handler = getHandler(request);

        if (handler == null) {
            response.setStatus(HttpServletResponse.SC_NOT_FOUND);
            return;
        }
        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) {
        MyHandlerAdapter a;
        for (MyHandlerAdapter adapter : handlerAdapters) {
            if(adapter.supports(handler)){
                return adapter;
            }
        }
        throw new IllegalArgumentException("handler adapter를 찾을 수 없습니다. handler = "+handler);
    }

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

---

이런 오류가 발생하는데 어디가 문제인제 잘 모르겠습니다..왜 이런걸까요?ㅠㅠㅠ