问题
Does anybody know where an iOS app can see the default headers that NSUrlRequest sets for an HTTP request?
Just creating NSUrlRequest with "http://.." NSURL and then asking: [request allHTTPHeaderFields] returns an empty dictionary. But I know that for example "Accept-Encoding" is set to "gzip". So I want to get all that fields and show them in a HTTP request demo.
I've also tried to swizzle [NSMutableURLRequest setValue:forHTTPHeaderField:], but it seems that it is not used by underlying API (NSURLRequest or NSURLConnection) to set those default fields I'm hunting for.
I'm making just a simple iOS demo which shows HTTP request and response information, so it doesn't really matters if it will be a public or private API used for that.
回答1:
Your app cannot. It's done all down in CFNetwork - Communicating with HTTP Servers. I believe it just adds missing header values not supplied by NSURLRequest.
The defaults are:
- USER-AGENT "AppName - Eng/1.0 CFNetwork/485.13.9 Darwin/10.7.0"
- ACCEPT "*/*"
- ACCEPT-LANGUAGE "en-us"
- ACCEPT-ENCODING "gzip, deflate"
- CONNECTION "keep-alive"
回答2:
hmm... maybe you might want to try within
- (NSURLRequest *)connection:(NSURLConnection *)connection willSendRequest:(NSURLRequest *)request redirectResponse:(NSURLResponse *)redirectResponse
method in your custom nsurlconnection class. although the documentation mentions something about redirects, this is certainly worth looking into.
回答3:
That may be an overkill, but based on Matt Gallagher's blog post I've created even more simpler local HTTP listener and sent a separate [mutableCopy]ed request to it to be able to read and output all HTTP headers that this request has.
Better solution must be to setup a local HTTP request catcher, it must look nicer I think, but for the scope of simple demo just to show all sent/received headers this solution is OK.
来源：https://stackoverflow.com/questions/5695914/nsurlrequest-where-an-app-can-find-the-default-headers-for-http-request