Using DownloadHandler with Dialog

Flow
1

by Using the DownloadHandler and a onCompleteListener sometimes I run into thw following Exception.
The download starts within a Dialog. If in the meantime the dialoge was closed the referenced Component is no longer available - I think that is the problem - is there a way to handle it?

2025-09-12 20:56:02,883 ERROR | http-nio-38443-exec-9 | o.a.c.c.C.[Tomcat].[localhost].[/].[springServlet]      | Servlet.service() for servlet [springServlet] in context with path [] threw exception [com.vaadin.flow.server.ServiceException: java.lang.NullPointerException: Cannot invoke "com.vaadin.flow.component.UI.access(com.vaadin.flow.server.Command)" because the return value of "com.vaadin.flow.server.streams.TransferContext.getUI()" is null] with root cause 
java.lang.NullPointerException: Cannot invoke "com.vaadin.flow.component.UI.access(com.vaadin.flow.server.Command)" because the return value of "com.vaadin.flow.server.streams.TransferContext.getUI()" is null
	at com.vaadin.flow.server.streams.TransferProgressAwareHandler$5.onComplete(TransferProgressAwareHandler.java:290)
	at com.vaadin.flow.server.streams.TransferUtil.lambda$transfer$1(TransferUtil.java:120)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at java.base/java.util.Collections$UnmodifiableCollection.forEach(Collections.java:1092)
	at com.vaadin.flow.server.streams.TransferUtil.transfer(TransferUtil.java:120)
	at com.vaadin.flow.server.streams.InputStreamDownloadHandler.handleDownloadRequest(InputStreamDownloadHandler.java:94)
	at com.vaadin.flow.server.streams.DownloadHandler.handleRequest(DownloadHandler.java:104)
	at com.vaadin.flow.server.communication.StreamRequestHandler.callElementResourceHandler(StreamRequestHandler.java:194)
	at com.vaadin.flow.server.communication.StreamRequestHandler.handleRequest(StreamRequestHandler.java:119)
	at com.vaadin.flow.server.VaadinService.handleRequest(VaadinService.java:1853)
	at com.vaadin.flow.server.VaadinServlet.service(VaadinServlet.java:398)
	at com.vaadin.flow.spring.SpringServlet.service(SpringServlet.java:106)
	at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:195)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140)
	at org.springframework.web.filter.CompositeFilter$VirtualFilterChain.doFilter(CompositeFilter.java:108)
	at org.springframework.web.filter.CompositeFilter$VirtualFilterChain.doFilter(CompositeFilter.java:108)
	at org.springframework.security.web.FilterChainProxy.lambda$doFilterInternal$3(FilterChainProxy.java:231)
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:365)
	at org.springframework.security.web.access.intercept.AuthorizationFilter.doFilter(AuthorizationFilter.java:101)
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374)
	at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:125)
	at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:119)
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374)
	at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:100)
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374)
	at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:179)
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374)
	at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63)
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374)
	at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:107)
	at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:93)
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374)
	at org.springframework.security.web.csrf.CsrfFilter.doFilterInternal(CsrfFilter.java:117)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374)
	at org.springframework.security.web.header.HeaderWriterFilter.doHeadersAfter(HeaderWriterFilter.java:90)
	at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:75)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374)
	at org.springframework.security.web.context.SecurityContextHolderFilter.doFilter(SecurityContextHolderFilter.java:82)
	at org.springframework.security.web.context.SecurityContextHolderFilter.doFilter(SecurityContextHolderFilter.java:69)
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374)
	at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:62)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374)
	at org.springframework.security.web.session.DisableEncodeUrlFilter.doFilterInternal(DisableEncodeUrlFilter.java:42)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374)
	at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:233)
	at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:191)
	at org.springframework.web.filter.CompositeFilter$VirtualFilterChain.doFilter(CompositeFilter.java:113)
	at org.springframework.web.filter.ServletRequestPathFilter.doFilter(ServletRequestPathFilter.java:52)
	at org.springframework.web.filter.CompositeFilter$VirtualFilterChain.doFilter(CompositeFilter.java:113)
	at org.springframework.web.filter.CompositeFilter.doFilter(CompositeFilter.java:74)
	at org.springframework.security.config.annotation.web.configuration.WebSecurityConfiguration$CompositeFilterChainProxy.doFilter(WebSecurityConfiguration.java:319)
	at org.springframework.web.filter.CompositeFilter$VirtualFilterChain.doFilter(CompositeFilter.java:113)
	at org.springframework.web.servlet.handler.HandlerMappingIntrospector.lambda$createCacheFilter$3(HandlerMappingIntrospector.java:243)
	at org.springframework.web.filter.CompositeFilter$VirtualFilterChain.doFilter(CompositeFilter.java:113)
	at org.springframework.web.filter.CompositeFilter.doFilter(CompositeFilter.java:74)
	at org.springframework.security.config.annotation.web.configuration.WebMvcSecurityConfiguration$CompositeFilterChainProxy.doFilter(WebMvcSecurityConfiguration.java:240)
	at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:362)
	at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:278)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140)
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140)
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140)
	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:483)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:116)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:344)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:398)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:903)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1740)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1189)
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:658)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:63)
	at java.base/java.lang.Thread.run(Thread.java:833)
2

It should definitely not blow up like this (sounds like a good report for GitHub)

My workaround would be to either don’t close dialog early or use another hook… e.g. started (it applicable in your use-case)

3

I close the dialog with the completed event. However, the user can click outside of the screen and close the dialog and so sometimes it happens that this error occur.
I will report in on GitHub.

4

Just in case it helps as workaround, there is a property to disable this behavior: setCloseOnOutsideClick(boolean)

1 Like
5

I think it is an intented behavior for security, i.e. downloads via non-attached components work. The older API worked the same with StreamResource being unregistered when component was detached. So exception was thrown also with that in similar use case, just different one.

So it looks like I need to make a new version of this file export example: Grid CSV export with Download button in a Dialog. You need have Anchor attached to view in order to not detach it while Dialog is closed by Button click. · GitHub

6

Blocking the start of a download from a detached component makes sense as a security feature, but this is about getting progress updates for a download that started while the component was still attached.

This should be quite easy to fix in the framework by capturing the UI instance when the download starts and then using that instance for any subsequent update.

1 Like
7

I’ve created Download progress listener not notified if owner component has been detached · Issue #22243 · vaadin/flow · GitHub