我如何才能在一个处理程序中使用更多的 http.Request？

Question

I have a basic middlewear it's a Logger function, and when I do body, err := ioutil.ReadAll(r.Body) in each of the next functions http.Request will be empty. But i want that the body contains information. What can I do?

Start:

r.HandleFunc("/login", server.Loger(server.GetTokenHandler()).ServeHTTP).Methods("POST")

So it's middlewear:

func (server Server) Loger(h http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        body, _ := ioutil.ReadAll(r.Body)
        server.Log.Info(r.URL, " Methods: ", r.Method, string(body))
        h.ServeHTTP(w, r) //Calls handler h
    })
}

And now r.Body will be empty:

func (server Server) GetTokenHandler()  http.Handler{
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        body, err := ioutil.ReadAll(r.Body)
        if err != nil{
            http.Error(w, "", 400)
            server.Log.Error(err)
            return
        }
        fmt.Print(string(body))
    })
}

Answer 1

The r.Body can be only read once. There is no way around it.

If multiple middleware need to access the data, you need to save it a byte slice and pass it to subsequent middlewares.

If the handler had a context, you could have passed the body data as a value in the context.

Another solution, which is a hack, is to store the data in a header field of the ReponseWriter. You should not forget to remove it when returning so that it's not sent out. Subsequent middleware may then access the data in the header.

func (server Server) ReadBody(h http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        body, _ := ioutil.ReadAll(r.Body)
        w.Header().Add("body", string(body))
        h.ServeHTTP(w, r) //Calls handler h
        w.Header().Del("body")
    })
}

Subsequent middleware will get the body data with the instruction data := w.Header().Get("body") . Note that a header value is a string, not a byte slice.