Document how to handle cancelled file downloads.

Fixes #9014

(cherry picked from commit 65d2baf)

1 files changed, 27 insertions, 2 deletions

diff --git a/documentation/articles/LettingTheUserDownloadAFile.asciidoc b/documentation/articles/LettingTheUserDownloadAFile.asciidoc
index 4b595fc6de..209ef27c38 100644
--- a/documentation/articles/LettingTheUserDownloadAFile.asciidoc
+++ b/documentation/articles/LettingTheUserDownloadAFile.asciidoc
@@ -62,8 +62,7 @@ along with the file to ensure the browser doesn't try to open the file
 even if it's is a file type that the browser knows how to deal with.
 
 [[lazily-determine-the-content-and-the-name-of-the-file-being-server]]
-Lazily determine the content and the name of the file being server
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+==== Lazily determine the content and the name of the file being server
 
 One can lazily determine the content of the file using a
 `StreamResource`. Yet the name of the file that is going to be
@@ -110,3 +109,29 @@ public class OnDemandFileDownloader extends FileDownloader {
   }
 }
 ....
+
+[[lazily-determine-the-content-and-the-name-of-the-file-being-server]]
+==== Cancelled downloads
+
+Since downloadable files may be quite big, and the download process may take time, the user might decide to
+cancel the download process. It this case `IOException` may be thrown by the web server. In this case the exception
+does not mean that something went wrong with the application, but it the. To prevent those exceptions to be logged, you can catch
+and ignore it as here:
+
+```java
+public class IgnoreCancelDownloader extends FileDownloader {
+
+    ...
+
+    @Override
+    public boolean handleConnectorRequest(final VaadinRequest request, final VaadinResponse response, final String path) {
+        try {
+            return super.handleConnectorRequest(request, response, path);
+        } catch (final IOException ignored) {
+            return true;
+        }
+    }
+}
+
+```
+Note that the exception is a sublclass of `IOException`, but the particular class depends of the web container.