如何使Go HTTP客户端不自动跟踪重定向？

Question

我目前正在Go中编写一些与REST API交互的软件.我正在尝试查询的REST API端点返回HTTP 302重定向以及指向资源URI的HTTP Location标头.

我正在尝试使用Go脚本来获取HTTP Location标头以供以后处理.

以下是我目前正在实现的功能:

package main

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

var BASE_URL = "https://api.stormpath.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(STORMPATH_API_KEY_ID, STORMPATH_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()

}

这对我来说有点像黑客.通过重写http.Client的CheckRedirect功能,我基本上是被迫把HTTP重定向错误一样(他们不是).

我已经看到其他几个地方建议使用HTTP传输而不是HTTP客户端 - 但我不知道如何使这项工作,因为我需要HTTP客户端,因为我需要使用HTTP Basic Auth与此REST通信API.

您是否可以告诉我一种使用基本身份验证发出HTTP请求的方法 - 虽然不遵循重定向 - 但这不涉及抛出错误和错误处理？

谢谢.

Answer 1

现在有一个更简单的解决方案:

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

这样,http包自动知道:"啊,我不应该遵循任何重定向",但不会抛出任何错误.来自源代码中的评论:

作为一种特殊情况,如果CheckRedirect返回ErrUseLastResponse,则返回最近的响应,其主体未闭合,并返回nil错误.

Answer 2

另一种选择,使用客户端本身,没有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:此解决方案适用于<1.7

Answer 3

这是可能的,但解决方案稍微扭转了问题.这是一个写为golang测试的示例.

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
}

您应该能够将上面的代码放入它自己的名为"redirects"的包中,并在获取所需的依赖项之后运行它

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

希望这可以帮助!

Answer 4

要使用不遵循重定向的基本身份验证发出请求，请使用接受 *请求的RoundTrip函数

这段代码

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))
}

输出

{
  "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"
  }
}