Simple steps to make it work
1. Create an extension with the integration studio
2. Create an action in that extensio that will receive any of your needed parameters for your jasper file and the return is binary data
3. Open the code of the generated extension and search for your action
4. Edit the code in a way it will pass the bytes from your pdf/doc/etc.. to the return of the action
4.1 Remember: not return the bytes, but pass the bytes to the return
5. Upload your extension to your application/enviroment if not already
6. Create and action from a button or from wherever you want
7. Inside the action created just now, call the action from the exension.
8. Use the "Download" action from the left bar and pass the bytes from the return of the extension action to the download action
9. Add the mymetype to the Download action accordingly to your jasper file (pdf/doc/html/etc..)
9.1 Example "application/pdf" To make it a pdf that will be opened in the browser (or downloaded as it happens in some browsers)
10. Publish and test it
Any doubts, I'm available
Hope it helped.