http - 扩展golang的http包

Question

我需要扩展 http 包来实现在状态中包含错误描述的非标准响应，即: 400 缺少必需的参数 而不是标准状态描述的 400 Bad request。

这是我的实际实现:

package main

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

type GatewayHandler int

func main() {
    var gh GatewayHandler

    http.ListenAndServe(":9000", gh)
}

func (gh GatewayHandler) ServeHTTP(res http.ResponseWriter, req *http.Request) {

    legacyApiUrl := "http://some-url.com" + req.URL.RequestURI()

    client := &http.Client{}
    request, _ := http.NewRequest(req.Method, legacyApiUrl, nil)
    response, _ := client.Do(request)
    res.Header().Set("Status", response.Status)
    for k, v := range response.Header {
        fmt.Println(k, ": ", v)
        i := ""
        for _, j := range v {
            i += j
        }
        res.Header().Set(k, i)
    }

    res.WriteHeader(response.StatusCode)

    if response.Status != "200 OK" {
        fmt.Println(response.Status)
    }

    result, _ := ioutil.ReadAll(response.Body)
    output := string(result)
    fmt.Println(output)

    io.WriteString(res, output)
}

一般来说，我需要从使用它的其他 URL 转发该状态，并且我需要保持它的兼容性。

非常感谢您。

约瑟夫

Answer 1

您可以使用http.Hijacker 接口(interface)https://golang.org/pkg/net/http/#Hijacker “劫持”(接管)服务器与客户端的 TCP 连接并向其写入自定义响应。这是示例的修改 https://golang.org/pkg/net/http/#example_Hijacker向客户端返回“400 Required parameter is missing”而不是标准的“400 Bad request”响应:

package main

import "net/http"

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        hj, ok := w.(http.Hijacker)
        if !ok {
            http.Error(w, "webserver doesn't support hijacking", http.StatusInternalServerError)
            return
        }
        conn, bufrw, err := hj.Hijack()
        if err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }
        // Don't forget to close the connection:
        defer conn.Close()
        // non-standard HTTP status text and an HTTP header are written;
        // end of the Headers part of the messages is marked by extra \r\n
        bufrw.WriteString("HTTP/1.1 400 Required parameter is missing\r\nContent-Type: text/html; charset=utf-8\r\n\r\n")
        // write the body of the HTTP response message
        bufrw.WriteString("400 Required parameter is missing\n")
        bufrw.Flush()
    })
    http.ListenAndServe(":9000", nil)
}

运行此程序并发送 curl 请求会产生所需的响应:

$ curl -i http://localhost:9000/
HTTP/1.1 400 Required parameter is missing
Content-Type: text/html; charset=utf-8

400 Required parameter is missing

扩展它以传播来自旧 API 服务器的其他响应应该很简单。

编辑
根据 HTTP 消息标准 (https://www.rfc-editor.org/rfc/rfc7230#section-3)，在示例程序中使用 \r\n\r\n 终止 HTTP 响应的 Headers 部分；为清楚起见，分开的 WriteString 调用 HTTP 响应的 header 和正文。