在 docker 镜像上从后端到前端的 CORS 失败

Question

因此，我在本地运行后端服务器，并在 localhost:8080 的 Docker 容器中运行前端。当我打开前端时，我得到：

Access to fetch at 'http://localhost:3000/myservice' from origin 'http://localhost:8080' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

我在网上有根，看到了各种版本的设置标题。没有一个起作用。我现在的样子是这样的：

func (m MyService) initializeRoutes() {
    m.router.HandleFunc(VERSION+"/stuff", corsHandler(b.getStuff)).Methods("GET")
}

func corsHandler(h http.HandlerFunc) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        log.Print("preflight detected: ", r.Header)
        w.Header().Add("Connection", "keep-alive")
        w.Header().Add("Access-Control-Allow-Origin", "*")
        w.Header().Add("Access-Control-Allow-Methods", "POST, OPTIONS, GET, DELETE, PUT")
        w.Header().Add("Access-Control-Allow-Headers", "content-type")
        w.Header().Add("Access-Control-Max-Age", "86400")

        // continue with my method
        h(w, r)
    }
}

func (m MyService) getStuff(w http.ResponseWriter, r *http.Request) {
    //Do what is required
}

但是无论我设置什么，我从一开始就会遇到相同的错误。有人知道我为什么会遇到这个问题以及如何解决它吗？

Answer 1

创建中间件：

func EnableCORS(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        w.Header().Add("Vary", "Origin")
        w.Header().Add("Vary", "Access-Control-Request-Method")

        if r.Header.Get("Origin") != "" {
            w.Header().Set("Access-Control-Allow-Origin", "*")
            if isPreflight(r) {
                w.Header().Set("Access-Control-Allow-Methods", "OPTIONS, PUT, PATCH, DELETE")
                w.Header().Set("Access-Control-Allow-Headers", "Authorization, Content-Type")

                w.WriteHeader(http.StatusOK)
                return
            }
            break
        }
        next.ServeHTTP(w, r)
    })
}

func isPreflight(r *http.Request) bool {
    return r.Method == http.MethodOptions && r.Header.Get("Access-Control-Request-Method") != ""
}

将中间件包裹在路由器周围：

r := http.NewServeMux()
http.ListenAndServe(":8080", EnableCors(r))

希望有帮助。

编辑2023-06-26：

正如 jub0bs 在评论中推荐的那样，使用 cors 包，其维护方式如下：

• https://github.com/jub0bs/cors
• https://github.com/rs/cors