[springboot/에러해결]nullpointerException, BeanInstantiationException 에러

프로젝트를 실행하고 웹에 접속하고 실행하면 자꾸 아래의 에러가 나타났다. 실행이 중단되는 건 아니였지만 왜 저런 에러가 나는지 궁금했다.

2023-02-18 00:40:40.561 ERROR 17756 --- [nio-8080-exec-4] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.bstarbackend.bstar.config.auth.dto.SessionUser]: Constructor threw exception; nested exception is java.lang.NullPointerException: Cannot invoke "com.bstarbackend.bstar.domain.user.Users.getName()" because "users" is null] with root cause

java.lang.NullPointerException: Cannot invoke "com.bstarbackend.bstar.domain.user.Users.getName()" because "users" is null
at com.bstarbackend.bstar.config.auth.dto.SessionUser.<init>(SessionUser.java:17) ~[main/:na]
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:78) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:na]
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:499) ~[na:na]
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:480) ~[na:na]
at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:211) ~[spring-beans-5.3.25.jar:5.3.25]
at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.constructAttribute(ModelAttributeMethodProcessor.java:332) ~[spring-web-5.3.25.jar:5.3.25]
at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.createAttribute(ModelAttributeMethodProcessor.java:220) ~[spring-web-5.3.25.jar:5.3.25]
at org.springframework.web.servlet.mvc.method.annotation.ServletModelAttributeMethodProcessor.createAttribute(ServletModelAttributeMethodProcessor.java:85) ~[spring-webmvc-5.3.25.jar:5.3.25]
at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.resolveArgument(ModelAttributeMethodProcessor.java:147) ~[spring-web-5.3.25.jar:5.3.25]
at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:122) ~[spring-web-5.3.25.jar:5.3.25]
at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:179) ~[spring-web-5.3.25.jar:5.3.25]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:146) ~[spring-web-5.3.25.jar:5.3.25]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117) ~[spring-webmvc-5.3.25.jar:5.3.25]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.3.25.jar:5.3.25]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.25.jar:5.3.25]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.25.jar:5.3.25]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1071) ~[spring-webmvc-5.3.25.jar:5.3.25]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:964) ~[spring-webmvc-5.3.25.jar:5.3.25]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.25.jar:5.3.25]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.25.jar:5.3.25]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:670) ~[tomcat-embed-core-9.0.71.jar:4.0.FR]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.25.jar:5.3.25]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:779) ~[tomcat-embed-core-9.0.71.jar:4.0.FR]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.71.jar:9.0.71]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:337) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:115) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:81) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:346) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:122) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:116) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:346) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:126) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:81) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:346) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:109) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:346) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:149) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:346) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:346) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:223) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:217) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:346) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.oauth2.client.web.OAuth2AuthorizationRequestRedirectFilter.doFilterInternal(OAuth2AuthorizationRequestRedirectFilter.java:178) ~[spring-security-oauth2-client-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.25.jar:5.3.25]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:346) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:103) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:89) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:346) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.header.HeaderWriterFilter.doHeadersAfter(HeaderWriterFilter.java:90) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:75) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.25.jar:5.3.25]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:346) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:112) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:82) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:346) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:55) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.25.jar:5.3.25]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:346) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.session.DisableEncodeUrlFilter.doFilterInternal(DisableEncodeUrlFilter.java:42) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.25.jar:5.3.25]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:346) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:221) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:186) ~[spring-security-web-5.7.7-SNAPSHOT.jar:5.7.7-SNAPSHOT]
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:354) ~[spring-web-5.3.25.jar:5.3.25]
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:267) ~[spring-web-5.3.25.jar:5.3.25]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.25.jar:5.3.25]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.25.jar:5.3.25]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.25.jar:5.3.25]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.25.jar:5.3.25]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.springframework.session.web.http.SessionRepositoryFilter.doFilterInternal(SessionRepositoryFilter.java:142) ~[spring-session-core-2.7.0.jar:2.7.0]
at org.springframework.session.web.http.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:82) ~[spring-session-core-2.7.0.jar:2.7.0]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.25.jar:5.3.25]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.25.jar:5.3.25]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:177) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:360) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:399) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:891) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1784) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.71.jar:9.0.71]
at java.base/java.lang.Thread.run(Thread.java:831) ~[na:na]

에러 양이 많지만, 첫번째 줄과 두번째 줄을 봐보면

2023-02-18 00:40:40.561 ERROR 17756 --- [nio-8080-exec-4] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.bstarbackend.bstar.config.auth.dto.SessionUser]: Constructor threw exception; nested exception is java.lang.NullPointerException: Cannot invoke "com.bstarbackend.bstar.domain.user.Users.getName()" because "users" is null] with root cause

java.lang.NullPointerException: Cannot invoke "com.bstarbackend.bstar.domain.user.Users.getName()" because "users" is null

Users entity class에서 users가 null이라서 getName을 할 수 없어 nullpointerException이 발생했고, 이로 인해 BeanInstantiationException 에러가 발생했다. 

 

그리고 세번째 줄을 보면 

at com.bstarbackend.bstar.config.auth.dto.SessionUser.<init>(SessionUser.java:17) ~[main/:na]

SessionUser에서도 문제가 있다는 걸 발견하고 SessionUser를 살펴봤다.

 

SessionUser는 생성자를 만들때 Users로 가져오는데 뭔가 이때 users가 null이라서 getName()에서 에러가 난 것 같았다.

 

users에 왜 null이 들어가는지 이해할 수 없어서 getName()에 breakpoint를 걸고 디버깅을 진행하며 확인한 결과

users에는 정상적으로 모든 값들이 잘 들어가고 있었다..

 

그래서 어디서 null이 들어갔는지 찾기 위해 SessionUser가 사용된 모든 코드들을 보며 디버깅을 진행했고.. 드디어 문제점을 발견했다!!

내가 예전에 작성했던 indexController에서 에러가 발생한 것이다. index 함수에서 getMapping으로 /main 페이지를 처리하는 과정에서, SessionUser로 선언되었던 user에 null값이 들어가서 이런 에러가 난 것이였다..! 예전에 작성한 코드여서 있는 줄도 몰랐는데.. 이 코드는 리액트와 연동하면서 필요없는 코드라서 그냥 다 지웠다. 

 

그러니까 에러가 없이 잘 동작했다!!!!

 

굳이 이 에러를 해결하지 않아도 됐지만, 도대체 어디서!! null이 들어가 nullpointerException이 일어났는지 너무 궁금했고, 문제가 되는 코드를 찾아 문제를 해결했다!