dta38159 2018-07-16 06:52
浏览 405
已采纳

如何使用proxy.ModifyResponse?

I've implemented the most basic Reverse Proxy to pull a page and then add some content to the body. Unfortunately my attempt to add to the html isn't taking effect. The code below just shows the original page but without the "monkeys" I prepended to the response. What additional calls are needed to get this to work? I eventually want to use this to replace css for custom css.

package main

import (
    "log"
    "net/http"
    "net/http/httputil"
    "net/url"
    "fmt"
    "github.com/PuerkitoBio/goquery"
    "bytes"
)

type Director func(*http.Request)

func (f Director) Then(g Director) Director {
    return func(req *http.Request) {
        f(req)
        g(req)
    }
}

func hostDirector(host string) Director {
    return func(req *http.Request) {
        req.Host = host
    }
}

func UpdateResponse(r *http.Response) error {
    doc, err := goquery.NewDocumentFromReader(r.Body)
    if err != nil{
        //log.New("Research")
        log.Fatal("Bad doc %v", err)
        return err
    }
    html, err := goquery.OuterHtml(doc.First())
    if err != nil{
        log.Fatal("Bad html %v", err)
        return err
    }
    fmt.Printf("Body %v", html)
    r.Write(bytes.NewBufferString("monkeys"+html))

    return nil
}

func main() {
    url, _ := url.Parse("http://cnn.com/")
    proxy := httputil.NewSingleHostReverseProxy(url)

    d := proxy.Director
    // sequence the default director with our host director
    proxy.Director = Director(d).Then(hostDirector(url.Hostname()))
    proxy.ModifyResponse = UpdateResponse
    http.Handle("/", proxy)
    log.Fatal(http.ListenAndServe(":9090", nil))
}
  • 写回答

1条回答 默认 最新

  • dongwu9972 2018-07-16 18:04
    关注

    Your ModifyResponse code is not modifying the response. In your code, you have:

    r.Write(bytes.NewBufferString("monkeys"+html))
    

    It seems that you are writing to the response, but nope. r is of *http.Response which has a Write method:

    func (r *Response) Write(w io.Writer) error
    

    The document says:

    Write writes r to w in the HTTP/1.x server response format, including the status line, headers, body, and optional trailer.

    Since bytes.Buffer also implements a io.Writer, the code compiles, but instead of write to the response from the buffer, it write the response to the buffer, which is absolutely undesired.

    The fact is, http.Response simply don't provide a way to modify its Body. It is clear that Bodey is an io.ReadCloser. What you can do is create a new io.ReadCloser with the body. Remember to change Content-Length field in the Header or it may cause problem.

    func UpdateResponse(r *http.Response) error {
        b, _ := ioutil.ReadAll(r.Body)
        buf := bytes.NewBufferString("Monkey")
        buf.Write(b)
        r.Body = ioutil.NopCloser(buf)
        r.Header["Content-Length"] = []string{fmt.Sprint(buf.Len())}
        return nil
    }
    

    Playground: https://play.golang.org/p/_Tyvo6GVN3x

    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论

报告相同问题?

悬赏问题

  • ¥15 MATLAB代码求涡量
  • ¥100 采用栈和深度优先算法对我的代码进行修改显示路径
  • ¥15 pointnet2包安装
  • ¥20 射频功率问题,解答者有酬谢!
  • ¥80 构建降雨和积水的预测模型
  • ¥15 #Qt Transform setTransform()在鼠标拖动移动视角是一致在原地不动,无法变换视角(细微观察似乎视图有在原地抖动),无法变换视角(细微观察似乎视图有在原地抖动)
  • ¥50 如何利用无人机拍摄的数码照片测量鸟卵的长短径
  • ¥100 github贡献者给与奖励
  • ¥15 使用DS18B20+ESP8266获取温度数据返回-127.00
  • ¥15 odbc代码新增sqlserver数据源