nullpointer exception on filedownload

[lordpixel]

Hi all
hi have a button rendered in a datatable that download a file.
Now the button is always present but the download may fail because the file is passe by a web service and i know that there is not file only when i call web service and not when i render the button.
Now when i click the button and the StreamedContent is null the page "explodes" ^^ and i get a bad nullpointer exception. Even if i use try catch statements...
There is something to return different from a null when there is no file?

Thanks

[dacian275]

You could have boolean value fileIsNull in your code that checks whether the file is null. Then, you could use the rendered or disabled attribute for button so that users can't download when the file is null.

[lordpixel]

I've fixed testing null before return . If the file is null i create a streamcontent from a fixed pdf file containing an alert....