💎 ClassCastException
Java 프로그램에서 클래스 형변환이 실패한 경우 발생하는 예외인 "java.lang.ClassCastException"의 내용을
보여줍니다. 이 예외는 클래스 형변환 시 타입이 호환되지 않을 때 발생하며,
이 경우 "edu.kh.mung.member.model.dto.Member" 클래스를 "java.lang.String"으로 캐스팅하려고 시도했지만 실패했다는 것을 의미합니다.
SEVERE: 경로 []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.ClassCastException: class edu.kh.mung.member.model.dto.Member cannot be cast to class java.util.List (edu.kh.mung.member.model.dto.Member is in unnamed module of loader org.apache.catalina.loader.ParallelWebappClassLoader @ccb4b1b; java.util.List is in module java.base of loader 'bootstrap')]을(를) 발생시켰습니다.
java.lang.ClassCastException: class edu.kh.mung.member.model.dto.Member cannot be cast to class java.util.List (edu.kh.mung.member.model.dto.Member is in unnamed module of loader org.apache.catalina.loader.ParallelWebappClassLoader @ccb4b1b; java.util.List is in module java.base of loader 'bootstrap')
at edu.kh.mung.Administrator.model.dao.AdministratorDAO.declarationPesitter(AdministratorDAO.java:174)
at edu.kh.mung.Administrator.model.service.AdministratorServiceImpl.declarationPesitter(AdministratorServiceImpl.java:178)
at edu.kh.mung.Administrator.controller.AjaxController.declarationPesitter(AjaxController.java:49)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:555)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:623)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:209)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:481)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:130)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:673)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:390)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:926)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1791)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)
at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.base/java.lang.Thread.run(Thread.java:834)🏆 해결!
오류에도 나와있듯이 반환하는 결과값이 String 타입으로는 받을수없는 여러개의 값이라 List형식으로 받아줘야 되는거였다..
🧨SQL조회 결과가 한줄이라고 SelectOne으로 조회하는게 아니고 컬럼의값이 많으면 무조건 List형식의 SelectList로 조회해야한다!!!!!
