问题
I am optimizing an Express JSON API for consumption by iOS & Android Apps and do not seem to be able to get Express to respond with the correct 304 header when the Apps specify an etag within the If-None-Match header.
I needn't setup Etag generation as Express was already providing those; however when the Apps specify that etag again in a second request; Express' response is still a 200 with the data, as you can see in my tests in Postman:
How can I enable this functionality?
Update: The iOS dev is seeing the correct 304 Not Modified responses from the Express server but I don't understand why I am not seeing them within Postman - Does Postman support such actions?
回答1:
I just stumble across this today, you need to disable Postman default behaviour of sending Cache-Control as none. To do this just go to settings and set that option to false.
来源：https://stackoverflow.com/questions/23997819/304-not-modified-when-if-none-match-is-valid