requirement to display locally downloaded files in a browser

I have a web app in asp which downloads pretty huge files to the user's local system. I have a requirement to open a viewer and read this files. Now the thing is this cannot be down using HTML5 because the filesystem APIs work on a sandboxed system and the file APIs can only read when the user has selected a file. I know the path of the downloaded files and I want a seamless experience. So I was hoping if there was any platform independent way I could interact with these files? I would prefer a client site code 开发者_如何学运维that could run in the browser but that seems impossible

You should be able to do this with a signed Java Applet.