I’m doing a mockup for a college project, and when I try to show a grid that implements a class called Grupo I recive a big error. I have been trying since several days many solutions and I have not found anything.
This is my Github repo: GitHub - rgarcres/aedo-rgc: TFG de Rubén García Crespo
The problem is when I try to create a group in the view “Crear Grupo”, when I try to enter in MisGruposView (the view were it shows the grid of groups that we have). It only happens when I try to show a Grip, but I have the same with Grid and it works.
Could be easier to help if you’d share the error message that you get.
Sorry I forget to summit it:
Anything in the server-side console or the browser’s JS console?
And also this on the inspector:
Is it what I have just send?
That’s what I referred to as the browser’s JS console. But I suspect the best information in this case is in the server-side console/log.
How can I see that? I’m sorry, I’m a beginner and I am learning all of these now.
That’s from where you launch your application. If you use an IDE, e.g IDEA, Eclipse or VS Code, then there’s a console with server-side messages that is typically at the bottom of the IDE below the code. If you run it from the command line, then the messages are shown in that terminal.
2025-04-07T10:50:45.376+02:00 ERROR 25500 — [io-8080-exec-10] c.v.flow.server.DefaultErrorHandler :
java.lang.NullPointerException: Cannot invoke “Object.getClass()” because “o” is null
at com.example.application.data.Grupo.equals(Grupo.java:44) ~[classes/:na]
at java.base/java.util.Objects.equals(Objects.java:64) ~[na:na]
at com.vaadin.flow.component.grid.AbstractGridSingleSelectionModel.isSelected(AbstractGridSingleSelectionModel.java:97) ~[vaadin-grid-flow-24.7.0.rc1.jar:na]
at com.vaadin.flow.component.grid.AbstractGridSingleSelectionModel.generateData(AbstractGridSingleSelectionModel.java:171) ~[vaadin-grid-flow-24.7.0.rc1.jar:na]
at com.vaadin.flow.data.provider.CompositeDataGenerator.lambda$generateData$0(CompositeDataGenerator.java:47) ~[flow-data-24.7.0.rc2.jar:24.7.0.rc2]
at java.base/java.lang.Iterable.forEach(Iterable.java:75) ~[na:na]
at com.vaadin.flow.data.provider.CompositeDataGenerator.generateData(CompositeDataGenerator.java:47) ~[flow-data-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.data.provider.DataCommunicator.generateJson(DataCommunicator.java:1519) ~[flow-data-24.7.0.rc2.jar:24.7.0.rc2]
at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197) ~[na:na]
at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197) ~[na:na]
at java.base/java.util.stream.IntPipeline$1$1.accept(IntPipeline.java:180) ~[na:na]
at java.base/java.util.stream.Streams$RangeIntSpliterator.forEachRemaining(Streams.java:104) ~[na:na]
at java.base/java.util.Spliterator$OfInt.forEachRemaining(Spliterator.java:712) ~[na:na]
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509) ~[na:na]
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499) ~[na:na]
at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921) ~[na:na]
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:na]
at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:682) ~[na:na]
at com.vaadin.flow.data.provider.DataCommunicator.getJsonItems(DataCommunicator.java:1474) ~[flow-data-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.data.provider.DataCommunicator.collectChangesToSend(DataCommunicator.java:1412) ~[flow-data-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.data.provider.DataCommunicator.performUpdate(DataCommunicator.java:1279) ~[flow-data-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.data.provider.DataCommunicator.flush(DataCommunicator.java:1233) ~[flow-data-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.data.provider.DataCommunicator.lambda$requestFlush$7258256f$1(DataCommunicator.java:1138) ~[flow-data-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.internal.StateTree.lambda$runExecutionsBeforeClientResponse$2(StateTree.java:397) ~[flow-server-24.7.0.rc2.jar:24.7.0.rc2]
at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184) ~[na:na]
at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:179) ~[na:na]
at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1708) ~[na:na]
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509) ~[na:na]
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499) ~[na:na]
at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151) ~[na:na]
at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174) ~[na:na]
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:na]
at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:596) ~[na:na]
at com.vaadin.flow.internal.StateTree.runExecutionsBeforeClientResponse(StateTree.java:392) ~[flow-server-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.server.communication.UidlWriter.encodeChanges(UidlWriter.java:394) ~[flow-server-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.server.communication.UidlWriter.createUidl(UidlWriter.java:170) ~[flow-server-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.server.communication.UidlRequestHandler.createUidl(UidlRequestHandler.java:187) ~[flow-server-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.server.communication.UidlRequestHandler.writeUidl(UidlRequestHandler.java:176) ~[flow-server-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.server.communication.UidlRequestHandler.synchronizedHandleRequest(UidlRequestHandler.java:139) ~[flow-server-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:63) ~[flow-server-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.server.VaadinService.handleRequest(VaadinService.java:1664) ~[flow-server-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.server.VaadinServlet.service(VaadinServlet.java:398) ~[flow-server-24.7.0.rc2.jar:24.7.0.rc2]
at com.vaadin.flow.spring.SpringServlet.service(SpringServlet.java:106) ~[vaadin-spring-24.7.0.rc2.jar:na]
at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) ~[tomcat-embed-core-10.1.36.jar:6.0]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:195) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:633) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:409) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:304) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:268) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.springframework.web.servlet.mvc.ServletForwardingController.handleRequestInternal(ServletForwardingController.java:142) ~[spring-webmvc-6.2.3.jar:6.2.3]
at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:178) ~[spring-webmvc-6.2.3.jar:6.2.3]
at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:51) ~[spring-webmvc-6.2.3.jar:6.2.3]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1088) ~[spring-webmvc-6.2.3.jar:6.2.3]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:978) ~[spring-webmvc-6.2.3.jar:6.2.3]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014) ~[spring-webmvc-6.2.3.jar:6.2.3]
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:914) ~[spring-webmvc-6.2.3.jar:6.2.3]
at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:590) ~[tomcat-embed-core-10.1.36.jar:6.0]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885) ~[spring-webmvc-6.2.3.jar:6.2.3]
at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) ~[tomcat-embed-core-10.1.36.jar:6.0]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:195) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) ~[tomcat-embed-websocket-10.1.36.jar:10.1.36]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-6.2.3.jar:6.2.3]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.2.3.jar:6.2.3]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-6.2.3.jar:6.2.3]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.2.3.jar:6.2.3]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-6.2.3.jar:6.2.3]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.2.3.jar:6.2.3]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:483) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:344) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:397) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:905) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1743) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1190) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:63) ~[tomcat-embed-core-10.1.36.jar:10.1.36]
at java.base/java.lang.Thread.run(Thread.java:1583) ~[na:na]
Well I have found the solution, it was the equals() method on the entity Grupo. Thanks you very much!
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