In html <a href> tag, how to call servlet before opening file dialog for download (save as)?

Question

Hi All,

I am developing a web-app where I want to provide a download link to users - so they can download a zip file from my server. Now, my requirement is that I want to execute some processing logic contained in a servlet before displaying the file dialog to the user for 'zip' files.

So If I write

<a href="abc.zip".......>

then it opens a file dialog asking the user to select the location where this file can be saved

But if I want a servlet's doGet method to do some preprocessing - say like building the zip file , then how can I first call the servlet and then open the file dialog.

Will the following snippet work?

 <a href="MyHandlerServlet;abc.zip".......>

Thanks for your help !!

Answer 1

 <a href="MyHandlerServlet?file=abc.zip">

The servlet would need to respond to the request with the zip file.

Answer 2

I would rather pass the filename as pathinfo instead of request parameter, e.g.

<a href="MyHandlerServlet/abc.zip">

Otherwise a certain widely used webbrowser developed by a team in Redmond (cough) would use MyHandlerServlet as filename during Save As. When passing the filename as pathinfo, you can obtain the requested file in the servlet by:

String filename = request.getPathInfo();

You only need to map the servlet on /MyHandlerServlet/* instead of /MyHandlerServlet. Also see this basic servlet example.