Go to Http error handling
I am a little confused about how error handling should be out of go. I've read so many posts about this but still can't seem to apply them in my code structure. I am a newbie so please help.
There is a main function that handles two apis: api1 and api2
func main() {
http.HandleFunc("/offers", api1)
http.HandleFunc("/getOffersList", api2)
err := http.ListenAndServe(":8080", nil)
if err != nil {
log.Fatal("ListenAndServe: ", err)
}
}
func api1(w http.ResponseWriter, req *http.Request) {
validateRequestHeader(w, req, "GET")
// code here....
}
func api2(w http.ResponseWriter, req *http.Request) {
validateRequestHeader(w, req, "POST")
//code here....
}
func validateRequestHeader(w http.ResponseWriter, req *http.Request, allowedMethod string) {
// allow cross domain AJAX requests
w.Header().Set("Content-Type", "application/json")
if origin := req.Header.Get("Origin"); origin != "" {
w.Header().Set("Access-Control-Allow-Origin", origin)
w.Header().Set("Access-Control-Allow-Methods", "POST, GET, OPTIONS, PUT, DELETE")
w.Header().Set("Access-Control-Allow-Headers",
"Accept, Content-Type, Content-Length, Accept-Encoding, X-CSRF-Token, Authorization")
}
// Stop here if its Preflighted OPTIONS request
if req.Method == "OPTIONS" {
return
}
if req.Method != allowedMethod {
response := "Only " + allowedMethod + " requests are allowed"
http.Error(w, response, http.StatusMethodNotAllowed)
return
}
}
In api1
and the api2
function validateRequestHeader
is called. If this becomes true, then in api1 / api2 the following code runs, which I don't want. How should this be handled?
if req.Method != allowedMethod {
response := "Only " + allowedMethod + " requests are allowed"
http.Error(w, response, http.StatusMethodNotAllowed)
return
}
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This blogpost has details on how to bind multiple handler functions, which is what it should do. This way you can have a validation handler, a logging handler, an authorization handler, etc. Etc. And just put them together.
Essentially
func validator(next http.Handler) http.Handler {
fn := func(w http.ResponseWriter, req *http.Request) {
if isRequestValid(req) {
// a valid request is passed on to next handler
next.ServeHTTP(w, req)
} else {
// otherwise, respond with an error
http.Error(w, "Bad request - Go away!", 400)
}
}
return http.HandlerFunc(fn)
}
func api1() http.Handler {
fn := func(w http.ResponseWriter, req *http.Request) {
// api 1 code
}
return http.HandlerFunc(fn)
}
func api2() http.Handler {
fn := func(w http.ResponseWriter, req *http.Request) {
// api 2 code
}
return http.HandlerFunc(fn)
}
And then put them together in your function main
.
func main() {
http.Handler("/offers", validate(api1()))
http.Handler("/getOffersList", validate(api2()))
err := http.ListenAndServe(":8080", nil)
if err != nil {
log.Fatal("ListenAndServe: ", err)
}
}
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