Go语言中实现绝对路径HTTP重定向的策略与实践

func Redirect(w ResponseWriter, r *Request, urlStr string, code int)

// Redirect replies to the request with a redirect to url, // which may be a path relative to the request path. func Redirect(w ResponseWriter, r *Request, urlStr string, code int) {     if u, err := url.Parse(urlStr); err == nil {         // If url was relative, make absolute by         // combining with request path.         // The browser would probably do this for us,         // but doing it ourselves is more reliable.          // NOTE(rsc): RFC 2616 says that the location         // line must be an absolute URI, like         // "http://www.google.com/redirect/",         // not a path like "/redirect/".         // Unfortunately, we don't know what to         // put in the host name section to get the         // client to connect to us again, so we can't         // know the right absolute URI to send back.         // Because of this problem, no one pays attention         // to the RFC; they all send back just a new path.         // So do we.         oldpath := r.URL.Path         if oldpath == "" { // should not happen, but avoid a crash if it does             oldpath = "/"         }         if u.Scheme == "" { // 关键判断：如果URL没有协议（scheme）             // no leading http://server             if urlStr == "" || urlStr[0] != '/' {                 // make relative path absolute                 olddir, _ := path.Split(oldpath)                 urlStr = olddir + urlStr             }              var query string             if i := strings.Index(urlStr, "?"); i != -1 {                 urlStr, query = urlStr[:i], urlStr[i:]             }              // clean up but preserve trailing slash             trailing := strings.HasSuffix(urlStr, "/")             urlStr = path.Clean(urlStr)             if trailing && !strings.HasSuffix(urlStr, "/") {                 urlStr += "/"             }             urlStr += query         }     }      w.Header().Set("Location", urlStr)     w.WriteHeader(code)      // ... (省略了处理响应体的部分) }

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package main  import (     "fmt"     "log"     "net/http"     "strings" )  func main() {     // 根路径处理函数     http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {         fmt.Fprintf(w, "欢迎访问根路径！当前路径: %sn", r.URL.Path)         fmt.Fprintf(w, "尝试访问 /relative-redirect 或 /absolute-redirect 或 /external-redirectn")     })      // 相对路径重定向示例     http.HandleFunc("/relative-redirect", func(w http.ResponseWriter, r *http.Request) {         // 这里的 "/target" 会被浏览器解释为相对于当前域的根路径         // 例如，如果当前请求是 http://localhost:8080/relative-redirect         // 重定向后会是 http://localhost:8080/target         log.Printf("执行相对路径重定向到 /target")         http.Redirect(w, r, "/target", http.StatusFound) // 302 Found     })      // 绝对路径重定向到同一域内的示例     http.HandleFunc("/absolute-redirect", func(w http.ResponseWriter, r *http.Request) {         // 动态构建包含协议和主机的完整URL         // r.URL.Scheme 在某些情况下可能为空（例如，在代理后），         // 可以使用 r.TLS != nil 来判断是否是HTTPS，或者依赖代理设置X-Forwarded-Proto         scheme := "http"         if r.TLS != nil || r.Header.Get("X-Forwarded-Proto") == "https" {             scheme = "https"         }          targetPath := "/target"         absoluteURL := fmt.Sprintf("%s://%s%s", scheme, r.Host, targetPath)          log.Printf("执行绝对路径重定向到 %s", absoluteURL)         http.Redirect(w, r, absoluteURL, http.StatusFound) // 302 Found     })      // 绝对路径重定向到外部URL的示例     http.HandleFunc("/external-redirect", func(w http.ResponseWriter, r *http.Request) {         externalURL := "https://www.google.com"         log.Printf("执行外部绝对路径重定向到 %s", externalURL)         http.Redirect(w, r, externalURL, http.StatusFound) // 302 Found     })      // 目标路径处理函数     http.HandleFunc("/target", func(w http.ResponseWriter, r *http.Request) {         fmt.Fprintf(w, "您已成功重定向到目标路径！当前路径: %sn", r.URL.Path)     })      fmt.Println("服务器正在监听 :8080...")     log.Fatal(http.ListenAndServe(":8080", nil)) }

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