I am new in adf. I have to consume a web service for download document in ADF. It will return an InputStream object and I don't have sample JSON response. Could any one help me.
Kind of depends on what exactly you want to do in ADF. In general you can create a Java class that interact with your REST service, and then expose that Java class as a data control that you can bind to an ADF UI.
One more thing you can try is using the Web Service Data Control (assuming you are on the latest JDEV) - it can consume REST services - https://tompeez.wordpress.com/2017/07/29/blog-using-external-rest-servies-part-1/