英文:
Can I check response when the request is redirected?
问题
我们可以注册CheckRedirect来在请求重定向时检查下一个请求。有没有办法在第一个请求被重定向时获取响应？
英文:
We can register CheckRedirect to check the next request when the request is redirected. Is there a way that I can get the response for the first request when it's redirected?
答案1
得分: 2
目前的实现方式似乎无法默认查看响应（除非你自己实现Do()的功能）。
请参考src/net/http/client.go#L384-L399：
如果应该重定向（shouldRedirect）响应，那么：
- 如果响应体很小，读取响应体以便底层TCP连接可以被重用。
- 如果读取失败，Transport也不会重用它，所以不需要检查错误。
- 如果响应没有ContentLength或者ContentLength小于等于maxBodySlurpSize（2KB），则将响应体拷贝到ioutil.Discard中。
- 关闭响应体。
- 如果响应头中没有"Location"字段，将err设置为"%d response missing Location header"的格式化错误信息。
- 更新base为req.URL。
- 将req添加到via切片中。
- 继续下一次循环。
英文:
The way it is currently implemented, it doesn't seem possible to have a look at the response by default (unless you implement yourself what Do() does).
See src/net/http/client.go#L384-L399:
if shouldRedirect(resp.StatusCode) {// Read the body if small so underlying TCP connection will be re-used.// No need to check for errors: if it fails, Transport won't reuse it anyway.const maxBodySlurpSize = 2 << 10if resp.ContentLength == -1 || resp.ContentLength <= maxBodySlurpSize {io.CopyN(ioutil.Discard, resp.Body, maxBodySlurpSize)}resp.Body.Close()if urlStr = resp.Header.Get("Location"); urlStr == "" {err = fmt.Errorf("%d response missing Location header", resp.StatusCode)break}base = req.URLvia = append(via, req)continue}
答案2
得分: 1
你想对第一个回复做什么？这将会相当无聊。
我认为最明智的做法是禁用自动跟随重定向（始终从CheckRedirect返回非nil错误），并自己处理重定向，在这种情况下，你可以完全访问所有的请求/响应。
英文:
What do you want to do with the first response? It will be pretty boring.
I think the most sensible thing would be to disable automatically following redirects (always return a non-nil error from CheckRedirect) and handle the redirection yourself in which case you have full access to all requests/responses.
答案3
得分: 0
我的解决方法是：
可以通过自定义的RoundTripper来修补任何HTTP请求/响应，包括重定向：
type RedirectChecker struct{}func (RedirectChecker) RoundTrip(req *http.Request) (*http.Response, error) {// 例如，在发送请求之前修补请求req.Header.Set("user-agent", "curl/7.64.1")resp, err := http.DefaultTransport.RoundTrip(req)if err == nil && resp != nil {switch resp.StatusCode {casehttp.StatusMovedPermanently,http.StatusFound,http.StatusTemporaryRedirect,http.StatusPermanentRedirect:// 例如，停止进一步的重定向// 大致相当于http.ErrUseLastResponseresp.StatusCode = http.StatusOK// 例如，读取Set-Cookie头// 不幸的是，cookie jar不能正确处理重定向// 这就是我来到这个问题的原因...fmt.Printf("%+v", resp.Cookies())}}}
httpClient := &http.Client{Transport: RedirectChecker{}}httpClient.Do(...)
英文:
My workaround for this:
Any http request / response could be patched within a custom RoundTripper, including redirects:
type RedirectChecker struct{}func (RedirectChecker) RoundTrip(req *http.Request) (*http.Response, error) {// e.g. patch the request before send itreq.Header.Set("user-agent", "curl/7.64.1")resp, err := http.DefaultTransport.RoundTrip(req)if err == nil && resp != nil {switch resp.StatusCode {casehttp.StatusMovedPermanently,http.StatusFound,http.StatusTemporaryRedirect,http.StatusPermanentRedirect:// e.g. stop further redirections// roughly equivalent to http.ErrUseLastResponseresp.StatusCode = http.StatusOK// e.g. read the Set-Cookie headers// unfortunately cookie jars do not handle redirects in a proper manner// and that's why I came to this question...fmt.Printf("%+v", resp.Cookies())}}}
httpClient := &http.Client{Transport: RedirectChecker{}}httpClient.Do(...)
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