Gin的FileFromFS无限重定向问题
目录
Gin的FileFromFS无限重定向问题
问题
在用Gin+React构建SPA应用时，想把React的构建产物直接通过//go:embed嵌入到go应用。结果出现了无限重定向的问题：
[GIN-debug] GET / --> main.d (3 handlers)
[GIN-debug] [WARNING] You trusted all proxies, this is NOT safe. We recommend you to set a value.
Please check https://pkg.go.dev/github.com/gin-gonic/gin#readme-don-t-trust-all-proxies for details.
[GIN-debug] Listening and serving HTTP on :8080
[GIN] 2025/08/19 - 16:44:29 | 301 | 0s | ::1 | GET "/"
[GIN] 2025/08/19 - 16:44:31 | 301 | 0s | ::1 | GET "/"
[GIN] 2025/08/19 - 16:44:31 | 301 | 0s | ::1 | GET "/"
[GIN] 2025/08/19 - 16:44:31 | 301 | 0s | ::1 | GET "/"
[GIN] 2025/08/19 - 16:44:31 | 301 | 0s | ::1 | GET "/"这个问题直接卡了我两天，以为是自己哪写错了，把各个AI问了个遍都改不对，怎么都没想到是gin框架的问题。要是一开始就去翻下issue就好了，有点过度依赖AI和信任流行库了。
解析
在使用gin.context.FileFromFS是，会将URL路径替换为文件路径。而标准库的serveFile在处理路径时如果有/index.html后缀会重定向会/路由。如果是从/路由获取index.html，就会导致无限循环重定向。
如下是一个复现问题的最小示例：
package main
import (
"embed"
"io/fs"
"net/http"
"github.com/gin-gonic/gin"
)
func main() {
run()
}
func run() {
r := gin.Default()
r.GET("/", d)
r.Run(":8080")
}
//go:embed all:web
var embedFS embed.FS
// transfer embed.FS to http.FileSystem
func getHttpFS(targetPath string) http.FileSystem {
fsys, err := fs.Sub(embedFS, targetPath)
if err != nil {
return nil
}
return http.FS(fsys)
}
func d(c *gin.Context) {
c.FileFromFS("index.html", getHttpFS("web"))
}阅读源码进行调试，可以看到urlpath的变化：
/ -> index.html
// github.com/gin-gonic/gin@v1.10.1 // context.go // #L1078-L087 // FileFromFS writes the specified file from http.FileSystem into the body stream in an efficient way. func (c *Context) FileFromFS(filepath string, fs http.FileSystem) { defer func(old string) { c.Request.URL.Path = old }(c.Request.URL.Path) c.Request.URL.Path = filepath // "/" -> "index.html" http.FileServer(fs).ServeHTTP(c.Writer, c.Request) }index.html -> /index.html
// go1.23.0 // http // fs.go // #L980-L987 func (f *fileHandler) ServeHTTP(w ResponseWriter, r *Request) { upath := r.URL.Path if !strings.HasPrefix(upath, "/") { upath = "/" + upath r.URL.Path = upath // "index.html" -> "/index.html" } serveFile(w, r, f.root, path.Clean(upath), true) }/index.html -> /
// go1.23.0
// http
// fs.go
// #L673-L683
// name is '/'-separated, not filepath.Separator.
func serveFile(w ResponseWriter, r *Request, fs FileSystem, name string, redirect bool) {
const indexPage = "/index.html"
// redirect .../index.html to .../
// can't use Redirect() because that would make the path absolute,
// which would be a problem running under StripPrefix
if strings.HasSuffix(r.URL.Path, indexPage) {
localRedirect(w, r, "./") // "/index.html" -> "/"
return
}解决方法
可以写一个专门的方法获取index.html，直接实现serveFile的逻辑，绕过FileFromFS。
func d(c *gin.Context) {
// c.FileFromFS("index.html", getHttpFS("web"))
indexFromFS(c, "index.html", getHttpFS("web"))
}
func indexFromFS(c *gin.Context, path string, fs http.FileSystem) {
file, err := fs.Open(path)
if err != nil {
log.Printf("file not found: %s, error: %v", path, err)
c.AbortWithStatus(404)
return
}
defer file.Close()
stat, err := file.Stat()
if err != nil {
log.Printf("file stat error: %s, error: %v", path, err)
c.AbortWithStatus(404)
return
}
c.Header("Content-Type", "text/html")
http.ServeContent(c.Writer, c.Request, path, stat.ModTime(), file)
}