NullReferenceException: Object reference not set to an instance of an object. AspNetCore._Views_Home__TeacherTable_cshtml+d__0.MoveNext() in _TeacherTable.cshtml, line 12 Stack Query Cookies Headers NullReferenceException: Object reference not set to an instance of an object. AspNetCore._Views_Home__TeacherTable_cshtml+d__0.MoveNext() in _TeacherTable.cshtml @foreach (var teacher in Model.Teachers) System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) Microsoft.AspNetCore.Mvc.Razor.RazorView+d__16.MoveNext() Student.cshtml이라는 View에서는 TeacherStudentViewModel을 데이터를 받아 Teacher 리스트를 모두 출력해주게 되어있는데, Student.cshtml의 FORM으로 전달하는 Controller내의 액션 로직에는 View()만 리턴하여 Teacher 데이터부분이 NULL이라 에러가 뜨는 것 같습니다. 이런 경우에 어떻게 해결하나요? 하나의 View Page에 ViewModel이 필요할 수도 ViewModel이 필요없을 수도 있는 상황에는 어떻게 처리하나요?
ELK 스택 (ElasticSearch, Logstash, Kibana) 으로 데이터 분석
"error" : "ElasticsearchIllegalArgumentException[failed to execute script]; nested: ScriptException[scripts of type [inline], operation [update] and lang [grovy] are disabled]; ", "status" : 400 이라고 에러나는데 왜그런거죠ㅠㅠ?
linear_model.LinearRegression 에서 iteration은 어떻게 정해지는지 궁금합니다. Gradient Descent 류의 방법을 사용하여 Regression한 것 같은데, iteration 수는 어떻게 정해 질까요? sci-kit learn 공식 홈페이지에 따로 설명은 없었습니다.
부모의 좌표를 받아서 해와 달을 스페이스바를 누를때 부모에게로 모이도록 하고싶습니다. public class move : MonoBehaviour { public Transform targetTransform; void Start () { } void Update () { if (Input.GetKey(KeyCode.Space)) { Move(); } } void Move() { Vector3 direction = targetTransform.position; transform.Translate(direction * Time.deltaTime); } 했는데 아무런 움직임이 없어요 ㅠㅠ
Traceback (most recent call last): File "C:/Python_Study/14. Advanced reading and writing file.py", line 43, in emp.name,emp.work_start,emp.work_finish,emp.wage_per_hour,emp.worked_hours(),emp.wage_of_the_day() File "C:/Python_Study/14. Advanced reading and writing file.py", line 23, in wage_of_the_day return self.worked_hours() self.wage_per_hour TypeError: unsupported operand type(s) for : 'NoneType' and 'int' 이런 에러가 납니다. 내용은 영상과 종일하게 넣은거같은데 뭐가 문젠지 잘 모르겠네요 int선언을 안해준 것인지.. ============================================================================= 추가적으로 이것저것 해보다보니 if식에서 if worked_hours>4 로 하면 위와같은 에러가 나는데 if worked_hours >=4 로 하면 에러가 안나네요..
remove(int index) 메소드 구현에 있어서 잘못된 부분이라 생각되는 부분을 올립니다. if (index ==0) ... else {...} 로 구현해야 된다고 생각합니다. 전체 예문은 아래와 같습니다. public T remove(int index) { // delete if (index < 0 || index >= size) return null; if (index == 0) return removeFirst(); else { Node<T> prev = getNode(index-1); return removeAfter(prev); } }
Loading class com.mysql.jdbc.Driver'. This is deprecated. The new driver class is com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary. Thu Jun 14 00:00:33 KST 2018 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification. java.sql.SQLException: The server time zone value '´???¹?±¹ ???ؽ?' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support. at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:127) at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:95) at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:87) at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:61) at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:71) at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:76) at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:862) at com.mysql.cj.jdbc.ConnectionImpl.(ConnectionImpl.java:444) at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:230) at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:226) at java.sql.DriverManager.getConnection(Unknown Source) at java.sql.DriverManager.getConnection(Unknown Source) at util.DatabaseUtil.getConnection(DatabaseUtil.java:14) at user.UserDAO.join(UserDAO.java:14) at org.apache.jsp.userJoinAction_jsp._jspService(userJoinAction_jsp.java:139) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:443) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330) at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1468) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Unknown Source) Caused by: com.mysql.cj.exceptions.InvalidConnectionAttributeException: The server time zone value '´???¹?±¹ ???ؽ?' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) at java.lang.reflect.Constructor.newInstance(Unknown Source) at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:59) at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:83) at com.mysql.cj.util.TimeUtil.getCanonicalTimezone(TimeUtil.java:128) at com.mysql.cj.protocol.a.NativeProtocol.configureTimezone(NativeProtocol.java:2201) at com.mysql.cj.protocol.a.NativeProtocol.initServerSession(NativeProtocol.java:2225) at com.mysql.cj.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:1391) at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:993) at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:852) ... 36 more java.lang.NullPointerException at user.UserDAO.join(UserDAO.java:15) at org.apache.jsp.userJoinAction_jsp._jspService(userJoinAction_jsp.java:139) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:443) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330) at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1468) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Unknown Source)
elif user_input is '0': 에서 0이 왜 스트링 형태로 되는 것인지 이해가 잘 가질 않습니다. 수업시간에 제가 뭘 놓친건지 모르겠네요. 어렴풋이 그냥 0이라고 했을 때 True가 되는 것과 '0'으로 해야 False가 된다는 것 정도만 알겠는데 False가 되어야 하는 것이면 반드시 '0'일 필요는 없지 않나요? 그런데 '1', '2', '3' 같은 다른 스트링형 숫자로하면 작동이 되질 않네요. '0'일 때에는 잘 작동하거든요. 기초적인 질문일지는 모르겠지만 이해가 가질 않아서 누군가 속시원히 답해주시면 좋겠습니다 ㅠㅠ
