Hi Goudham,
Let me put my points for your requirement. You have a UI5 application which display details about materials. There you have a tab which lists all the documents attached to that material. User clicks on any attachment and that attachment is displayed to the user.
If I am correct with the above requirement, I do not see downloading all the attachments in one shot. First of all you need a call of query and list all the available attachments. Now when the user clicks on any particular attachment, download only that attachment with the help of GET_STREAM.
Let me know if I was wrong in understanding your scenario.
Regards,
Ekansh