"如何使 Go HTTP 客戶端不自動跟隨重定向？"

Question

我目前正在用 Go 編寫一些與 REST API 交互的軟件。 我嘗試查詢的 REST API 端點返回一個 HTTP 302 重定向以及一個指向資源 URI 的 HTTP Location 標頭。

我正在嘗試使用我的 Go 腳本來獲取 HTTP Location 標頭以供以后處理。

這是我目前為實現此功能所做的工作：

package main

import (
        "errors"
        "fmt"
        "io/ioutil"
        "net/http"
)

var BASE_URL = "https://api.example.com/v1"
var STORMPATH_API_KEY_ID = "xxx"
var STORMPATH_API_KEY_SECRET = "xxx"

func noRedirect(req *http.Request, via []*http.Request) error {
        return errors.New("Don't redirect!")
}

func main() {

        client := &http.Client{
            CheckRedirect: noRedirect
        }
        req, err := http.NewRequest("GET", BASE_URL+"/tenants/current", nil)
        req.SetBasicAuth(EXAMPLE_API_KEY_ID, EXAMPLE_API_KEY_SECRET)

        resp, err := client.Do(req)

        // If we get here, it means one of two things: either this http request
        // actually failed, or we got an http redirect response, and should process it.
        if err != nil {
            if resp.StatusCode == 302 {
                fmt.Println("got redirect")
            } else {
                panic("HTTP request failed.")
            }
        }
        defer resp.Body.Close()

}

Answer 1

現在有一個更簡單的解決方案：

client := &http.Client{
    CheckRedirect: func(req *http.Request, via []*http.Request) error {
        return http.ErrUseLastResponse
    },
}

這樣， http包自動知道：“啊，我不應該遵循任何重定向”，但不會拋出任何錯誤。 從源代碼中的注釋：

作為一種特殊情況，如果 CheckRedirect 返回 ErrUseLastResponse，則返回最新的響應，其主體未關閉，並帶有一個 nil 錯誤。

Answer 2

另一種選擇，使用客戶端本身，沒有 RoundTrip：

// create a custom error to know if a redirect happened
var RedirectAttemptedError = errors.New("redirect")

client := &http.Client{}
// return the error, so client won't attempt redirects
client.CheckRedirect = func(req *http.Request, via []*http.Request) error {
        return RedirectAttemptedError
}
// Work with the client...
resp, err := client.Head(urlToAccess)

// test if we got the custom error
if urlError, ok := err.(*url.Error); ok && urlError.Err == RedirectAttemptedError{
        err = nil   
}

更新：此解決方案適用於 go < 1.7

Answer 3

這是可能的，但解決方案稍微顛倒了問題。 這是一個編寫為 golang 測試的示例。

package redirects

import (
    "github.com/codegangsta/martini-contrib/auth"
    "github.com/go-martini/martini"
    "net/http"
    "net/http/httptest"
    "testing"
)

func TestBasicAuthRedirect(t *testing.T) {
    // Start a test server
    server := setupBasicAuthServer()
    defer server.Close()

    // Set up the HTTP request
    req, err := http.NewRequest("GET", server.URL+"/redirect", nil)
    req.SetBasicAuth("username", "password")
    if err != nil {
        t.Fatal(err)
    }

    transport := http.Transport{}
    resp, err := transport.RoundTrip(req)
    if err != nil {
        t.Fatal(err)
    }
    // Check if you received the status codes you expect. There may
    // status codes other than 200 which are acceptable.
    if resp.StatusCode != 200 && resp.StatusCode != 302 {
        t.Fatal("Failed with status", resp.Status)
    }

    t.Log(resp.Header.Get("Location"))
}


// Create an HTTP server that protects a URL using Basic Auth
func setupBasicAuthServer() *httptest.Server {
    m := martini.Classic()
    m.Use(auth.Basic("username", "password"))
    m.Get("/ping", func() string { return "pong" })
    m.Get("/redirect", func(w http.ResponseWriter, r *http.Request) {
        http.Redirect(w, r, "/ping", 302)
    })
    server := httptest.NewServer(m)
    return server
}

您應該能夠將上述代碼放入它自己的名為“redirects”的包中，並在使用獲取所需的依賴項后運行它

mkdir redirects
cd redirects
# Add the above code to a file with an _test.go suffix
go get github.com/codegangsta/martini-contrib/auth
go get github.com/go-martini/martini
go test -v

希望這可以幫助！

Answer 4

要使用不遵循重定向的基本身份驗證發出請求，請使用接受 *請求的RoundTrip函數

這段代碼

package main

import (
    "fmt"
    "io/ioutil"
    "net/http"
    "os"
)

func main() {
    var DefaultTransport http.RoundTripper = &http.Transport{}

    req, _ := http.NewRequest("GET", "http://httpbin.org/headers", nil)
    req.SetBasicAuth("user", "password")

    resp, _ := DefaultTransport.RoundTrip(req)
    defer resp.Body.Close()
    contents, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        fmt.Printf("%s", err)
        os.Exit(1)
    }
    fmt.Printf("%s\n", string(contents))
}

產出

{
  "headers": {
    "Accept-Encoding": "gzip", 
    "Authorization": "Basic dXNlcjpwYXNzd29yZA==", 
    "Connection": "close", 
    "Host": "httpbin.org", 
    "User-Agent": "Go 1.1 package http", 
    "X-Request-Id": "45b512f1-22e9-4e49-8acb-2f017e0a4e35"
  }
}

Answer 5

作為評分最高的答案的補充，

可以控制顆粒大小

func myCheckRedirect(req *http.Request, via []*http.Request, times int) error {
    err := fmt.Errorf("redirect policy: stopped after %d times", times)
    if len(via) >= times {
        return err
    }
    return nil
}

...

    client := &http.Client{
        CheckRedirect: func(req *http.Request, via []*http.Request) error {
            return myCheckRedirect(req, via, 1)
        },
    }

參考： https ://golangbyexample.com/http-no-redirect-client-golang/