HTTP responses with code 3xx and empty 'Locati

问题:

I'm connecting to URLs with Java (HttpURLConnection).

I have noticed that in some cases, the response code is 3xx but the 'Location' header is empty.

How does a client browser know where to redirect after receiving this kind of HTTP response?

Thanks

回答1:

Not all 3xx replies can redirect automatically.

300 provides multiple URLs in the response body, not in the Location header. The client/user has to decide which one to retrieve next.

301, 302, 303, and 307 provide a Location only if the next URL is known. Otherwise, the client/user has to decide what to do next.

304 is not a redirect. It is a response to a conditional GET, where the requested content has not changed since the requested criteria was last satisfied.

305 always provides a Location to the required proxy to connect to.

306 is not used anymore.

回答2:

If you look at the HTTP spec on some of the 3xx status codes, some of them only SHOULD provide a Location header.

How does a client browser know where to redirect after receiving this kind of HTTP response?

It doesn't. It's up to the client to handle what to do in that case.