Question

I am currently working on a GWT application that requires report
printing. The use can select report parameters from a screen, and
upon clicking print we would like to display the file as it is being
generated. Currently we have server side code that is generating HTML
and writing it to a file. When the user clicks print, an RPC is being
made to pass the report parameters to the server and begin the
report. A second RPC is made after the report has started to obtain
the report’s URL. From here, we are creating a Frame and setting the
URL to be the URL retrieved by the second RPC.

The issue I am running into, is that when setUrl gets
called, it only displays as much HTML that was contained in the file
at the time of the call. What would be the best way to refresh just
the frame containing the HTML report? It appears making subsequent
calls to setUrl passing in the same Url each time would do the trick,
but it actually doesn’t seem to contain the additional content that
would’ve been written since the last call. It is also resetting the
vertical scroll bar’s position each time back to the top of the bar
which is something else I would like to prevent.

Is there a better way to go about doing this?

Answer 1

I think it would be better to request HTML in chunks from GWT and render them as they arrive. Doing this with ajax instead of wholesale refreshes will enable better behavior with the scrollbar, eliminate flashing, get around caching problems, and will also let you add some feedback like a progress bar, estimated time remaining, etc.

There’s a lot more infrastructure required for this, but your suggested solution doesn’t seem quite appropriate for the task.