안녕하세요.

Spring으로 간단한 로그인을 짜고 있습니다.

로그인 기능을 만들었고 실행을 했을 때 겉보기에는 문제없이 돌아갑니다.

하지만 자바 콘솔에 오류가 하나 뜨더라구요.

먼저 코드는 이렇게 짰습니다.

@Controller
@RequestMapping("/member/*")
public class MemberController {
    private static final Logger logger = LoggerFactory.getLogger(MemberController.class);
    int i = 0;

    @Inject
    MemberService memberService;

    @RequestMapping("login.do")
    public String login() {
        return "member/login";
    }

    @RequestMapping("loginCheck.do")
    public ModelAndView loginCheck(@ModelAttribute MemberVO vo, Model model, BookMarkVO bookVO, HttpSession session, HttpServletRequest request)
            throws URISyntaxException, ClientProtocolException, IOException {
        boolean result = memberService.loginCheck(vo, session);

        ModelAndView mav = new ModelAndView();
        if (result == true || session.getAttribute("userId") != null) { 
            session.setMaxInactiveInterval(1800);
            mav.setViewName("home");
            mav.addObject("msg", "success");

            System.out.println("로그인성공");

            MemberVO memberInfo = memberService.viewMember(vo);
            System.out.println("memberID: " + memberInfo.getUserId());
        } else {
            mav.setViewName("member/login");
            mav.addObject("msg", "failure");
        }

        return mav;
    }
}

 로그인을 하면 세션을 가져와 30분 동안 유지하고 Sysout으로 현재 로그인 한 멤버의 아이디를 콘솔에 찍도록 했습니다.

로그인 후 다음 화면으로 잘 넘어가고 다른 기능들도 잘 되는데 자바 콘솔창에는 이렇게 뜹니다.

로그인성공
memberID: admin
로그인성공
7월 19, 2021 5:17:35 오후 org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: 경로 [/login]의 컨텍스트 내의 서블릿 [appServlet]을(를) 위한 Servlet.service() 호출이, 근본 원인(root cause)과 함께, 예외 [Request processing failed; nested exception is java.lang.NullPointerException: Cannot invoke "com.example.login.model.member.dto.MemberVO.getUserId()" because "memberInfo" is null]을(를) 발생시켰습니다.
java.lang.NullPointerException: Cannot invoke "com.example.login.model.member.dto.MemberVO.getUserId()" because "memberInfo" is null
    at com.example.login.controller.member.MemberController.loginCheck(MemberController.java:95)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:564)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:114)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:626)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1707)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:832)

 처음엔 잘 들고왔는데 로그인성공이 한 번 더 뜨면서 memberInfo.getUserId()(정확하게는 memberInfo) 이 값이 null이라고 뜨더라구요.

일단 제 생각은 코드가 2번 돌아 2번째에는 member에 대한 dao, service가 돌지 않아 memberInfo가 null이라고 생각이 듭니다.

왜 로그인하고 코드가 2번 도는지 궁금합니다.