I'm trying to use Golang middleware to run after handling Gorilla Mux routing, in order to change the response of each request.
Code sample see below. Currently it returns 'run before, run test', goal is to return 'run before, run test, run after' using the runsafter middleware.
Is something like this possible with Gorilla Mux?
package main
import (
"fmt"
"github.com/gorilla/mux"
"net/http"
)
func runsbefore(h http.Handler) http.Handler {
fn := func(w http.ResponseWriter, r *http.Request) {
w.Write([]byte("run before, "))
h.ServeHTTP(w, r)
}
return http.HandlerFunc(fn)
}
func runsafter(h http.Handler) http.Handler {
fn := func(w http.ResponseWriter, r *http.Request) {
w.Write([]byte("run after, "))
h.ServeHTTP(w, r)
}
return http.HandlerFunc(fn)
}
func runtest(w http.ResponseWriter, r *http.Request) {
w.Write([]byte("run test, "))
}
func main() {
fmt.Println("Server starting on port 8000")
r := mux.NewRouter()
r.HandleFunc("/", runtest).Methods("GET")
http.ListenAndServe(":8000", runsbefore(r))
// something like: http.ListenAndServe(":8000", runsbefore(r(runsafter)))
}
Use
http.ListenAndServe(":8000", runsAfter(runsbefore(r)))
and fix the error in runsAfter:
func runsafter(h http.Handler) http.Handler {
fn := func(w http.ResponseWriter, r *http.Request) {
h.ServeHTTP(w, r)
w.Write([]byte("run after, "))
}
return http.HandlerFunc(fn)
}
Related
I use a specific middleware for specific set of routes
r.Route("/platform", func(r chi.Router) {
r.Use(authService.AuthMiddleware)
r.Get("/{id}/latest", RequestPlatformVersion)
})
Now how can I access id url param inside this AuthMiddleware middleware
func (s *Service) AuthMiddleware(h http.Handler) http.Handler {
fn := func(w http.ResponseWriter, r *http.Request) {
fmt.Println(chi.URLParam(r, "id"))
id := chi.URLParam(r, "id")
if id > 100 {
http.Error(w, errors.New("Error").Error(), http.StatusUnauthorized)
return
}
}
return http.HandlerFunc(fn)
}
However, the id param prints as an empty string even though the middleware is being ran and a specific route is being called
You put your chi.URLParam before the path param {id} and you forgot to put .ServeHTTP(w, r) at the middleware. If you don't put that thing, your request will not go inside the path inside the route.
this is the working example:
package main
import (
"fmt"
"net/http"
"github.com/go-chi/chi"
)
func AuthMiddleware(h http.Handler) http.Handler {
fn := func(w http.ResponseWriter, r *http.Request) {
fmt.Println(chi.URLParam(r, "id"))
h.ServeHTTP(w, r)
}
return http.HandlerFunc(fn)
}
func main() {
r := chi.NewRouter()
r.Route("/platform/{id}", func(r chi.Router) {
r.Use(AuthMiddleware)
r.Get("/latest", func(rw http.ResponseWriter, r *http.Request) {
fmt.Println("here ", chi.URLParam(r, "id")) // <- here
})
})
http.ListenAndServe(":8080", r)
}
I move the {id} to platform/{id} so the middleware got the id path value, and add h.ServeHTTP(w, r) inside the middleware.
try to access http://localhost:8080/platform/1/latest
the output will be:
1
here 1
UPDATE
It is not good to run the validation after the code, you must fix the way you define the path, and move the .ServeHTTP after the validation.
This is the example:
package main
import (
"errors"
"fmt"
"net/http"
"strconv"
"github.com/go-chi/chi"
)
func AuthMiddleware(h http.Handler) http.Handler {
fn := func(w http.ResponseWriter, r *http.Request) {
fmt.Printf("Middleware First, id: %+v\n", chi.URLParam(r, "id"))
id, _ := strconv.Atoi(chi.URLParam(r, "id"))
if id > 100 {
http.Error(w, errors.New("Error").Error(), http.StatusUnauthorized)
return
}
h.ServeHTTP(w, r)
}
return http.HandlerFunc(fn)
}
func main() {
r := chi.NewRouter()
// This works too ()
// r.Route("/platform/{id}", func(r chi.Router) {
// r.Use(AuthMiddleware)
// r.Get("/latest", func(rw http.ResponseWriter, r *http.Request) {
// fmt.Println("second: ", chi.URLParam(r, "id")) // <- here
// })
// })
// Other Solution (Wrapping Middleware)
r.Route("/platform", func(r chi.Router) {
r.Get("/{id}/latest", AuthMiddleware(http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
fmt.Println("second: ", chi.URLParam(r, "id")) // <- here
})).ServeHTTP)
})
http.ListenAndServe(":8080", r)
}
What’s the equivalent to middleware handlers in Google Cloud Functions?
In standard approach, normally I do:
router.Handle("/receive", middlewares.ErrorHandler(MyReceiveHandler))
And then, in the middleware:
type ErrorHandler func(http.ResponseWriter, *http.Request) error
func (fn ErrorHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
err := fn(w, r)
if err == nil {
return
}
log.Printf("An error accured: %v", err)
clientError, ok := err.(errors.BaseError)
if !ok {
w.WriteHeader(500)
return
}
w.WriteHeader(clientError.GetStatusCode())
w.Write([]byte(clientError.Error()))
}
In AWS Lambda, I can achieve the same thing using, for example:
func main() {
lambda.Start(
middlewares.Authentication(Handler),
)
}
But I could not find a way to do this in GCP Functions.
How would it work?
Can you help me?
Let's say you start with the following server code in your development environment:
package main
import (
"fmt"
"log"
"net/http"
)
func main() {
http.Handle("/", MiddlewareFinalMsg(" Goodbye!", http.HandlerFunc(HelloWorld)))
if err := http.ListenAndServe(":8080", nil); err != nil {
log.Fatal(err)
}
}
func MiddlewareFinalMsg(msg string, h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
h.ServeHTTP(w, r)
fmt.Fprint(w, msg)
})
}
func HelloWorld(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "text/plain")
fmt.Fprint(w, "Hello, World!")
}
As far as I can tell, GCF requires its entry point to be an exported identifier of type func(http.ResponseWriter, *http.Request) (not http.HandlerFunc, not http.Handler); therefore, if you have a http.Handler, you'll need to select its ServeHTTP method explicitly to obtain a function of the expected type. However, that identifier can be a package-level function, a method, or a variable.
Here is how you can adapt the code above for GCF:
package p
import (
"fmt"
"net/http"
)
// use F as your GCF's entry point
var F = MiddlewareFinalMsg(" Goodbye!", http.HandlerFunc(HelloWorld)).ServeHTTP
func MiddlewareFinalMsg(msg string, h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
h.ServeHTTP(w, r)
fmt.Fprint(w, msg)
})
}
func HelloWorld(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "text/plain")
fmt.Fprint(w, "Hello, World!")
}
What's the best way to chain middlewares while using julienschmidt/httprouter?
As far as I have googled, http.HandlerFunc accepts functions only in the form func (w ResponseWriter, r *Request) whereas httprouter.Handle functions are of the form func (w http.ResponseWriter, r *http.Request, ps httprouter.Params).
How to I chain middlewares without converting the httprouter.Handle function into http.HandlerFunc?
For example:
My routes.go is of the form,
router := httprouter.New()
router.POST("/api/user/create", middlewares.EscapeStringsMiddleware(User.CreateUser))
log.Fatal(http.ListenAndServe(":8000", router))
How do I write middleware functions for the above mentioned route?
Already tried methods:
1.
func EscapeStringsMiddleware(next http.Handler) httprouter.Handle {
return func (response http.ResponseWriter, request *http.Request, ps httprouter.Params) {
err := request.ParseForm()
if err != nil {
panic(err)
}
for key, values := range request.Form {
for i, value := range values {
value = template.HTMLEscapeString(value)
value = template.JSEscapeString(value)
request.Form[key][i] = value
}
}
next.ServeHTTP(response, request)
}
}
Error obtained:
cannot use User.CreateUser (type func(http.ResponseWriter, *http.Request, httprouter.Params)) as type http.Handler in argument to middlewares.EscapeStringsMiddleware:
func(http.ResponseWriter, *http.Request, httprouter.Params) does not implement http.Handler (missing ServeHTTP method)
2.
func EscapeStringsMiddleware(next httprouter.Handle) httprouter.Handle {
return func (response http.ResponseWriter, request *http.Request, ps httprouter.Params) {
err := request.ParseForm()
if err != nil {
panic(err)
}
for key, values := range request.Form {
for i, value := range values {
value = template.HTMLEscapeString(value)
value = template.JSEscapeString(value)
request.Form[key][i] = value
}
}
next.ServeHTTP(response, request)
}
}
Error obtained:
next.ServeHTTP undefined (type httprouter.Handle has no field or method ServeHTTP)
Also how do I chain multiple middleware?
For example,
router.POST("/api/user/create", middlewares.VerifyCSRF(middlewares.EscapeStringsMiddleware(User.CreateUser)))
This issue is not with your middleware handler. You are getting errs because User.CreateUser is not of type http.Handler.
Try this pattern :
The important bit is to return a http.Handler and wrap func(w http.ResponseWriter, r *http.Request) with http.HandlerFunc.
func Handler() http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
// do stuff
})
}
go source :
// The HandlerFunc type is an adapter to allow the use of
// ordinary functions as HTTP handlers. If f is a function
// with the appropriate signature, HandlerFunc(f) is a
// Handler that calls f.
type HandlerFunc func(ResponseWriter, *Request)
// ServeHTTP calls f(w, r).
func (f HandlerFunc) ServeHTTP(w ResponseWriter, r *Request) {
f(w, r)
}
Based on your feedback:
httprouter.Handle does not implement ServeHTTP. It is called directly. For example : next(w, r, ps)
Below you will find examples of middleware handlers.
// Middleware without "github.com/julienschmidt/httprouter"
func StdToStdMiddleware(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
// do stuff
next.ServeHTTP(w, r)
})
}
// Middleware for a standard handler returning a "github.com/julienschmidt/httprouter" Handle
func StdToJulienMiddleware(next http.Handler) httprouter.Handle {
return func(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
// do stuff
next.ServeHTTP(w, r)
}
}
// Pure "github.com/julienschmidt/httprouter" middleware
func JulienToJulienMiddleware(next httprouter.Handle) httprouter.Handle {
return func(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
// do stuff
next(w, r, ps)
}
}
func JulienHandler() httprouter.Handle {
return func(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
// do stuff
}
}
func StdHandler() http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
// do stuff
})
}
func main() {
router := httprouter.New()
router.POST("/api/user/create", StdToJulienMiddleware(StdHandler()))
router.GET("/api/user/create", JulienToJulienMiddleware(JulienHandler()))
log.Fatal(http.ListenAndServe(":8000", router))
}
From https://github.com/cnvrtly/adaptr lib where adapters are also added to chain request middleware functions.
func compatibleHandler(h http.Handler, httprParamsCtxKey interface{}) httprouter.Handle {
return toHttpRouterHandle(h, httprParamsCtxKey)
}
func toHttpRouterHandle(h http.Handler, httprParamsCtxKey interface{}) func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
return func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
if httprParamsCtxKey != nil {
r = SetCtxValue(r, httprParamsCtxKey, p)
}
h.ServeHTTP(w, r)
}
}
If you are looking for example/idea how to define routes: https://github.com/cnvrtly/golang-appengine-seed
I'm using Julien Schmidt's router for GoLang and trying to get it working with Alice to chain middleware. I'm getting this error:
cannot use commonHandlers.ThenFunc(final) (type http.Handler) as type httprouter.Handle in argument to router.GET
and I'm not quite sure why.
My code is:
package main
import (
"log"
"net/http"
"github.com/julienschmidt/httprouter"
"github.com/justinas/alice"
"gopkg.in/mgo.v2"
//"gopkg.in/mgo.v2/bson"
)
func middlewareOne(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
log.Println("Executing middlewareOne")
next.ServeHTTP(w, r)
log.Println("Executing middlewareOne again")
})
}
func middlewareTwo(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
log.Println("Executing middlewareTwo")
if r.URL.Path != "/" {
return
}
next.ServeHTTP(w, r)
log.Println("Executing middlewareTwo again")
})
}
func final(w http.ResponseWriter, r *http.Request) {
log.Println("Executing finalHandler")
w.Write([]byte("OK"))
}
func main() {
session, err := mgo.Dial("conn-string")
if err != nil {
panic(err)
}
defer session.Close()
session.SetMode(mgo.Monotonic, true)
commonHandlers := alice.New(middlewareOne, middlewareTwo)
router := httprouter.New()
router.GET("/", commonHandlers.ThenFunc(final))
http.ListenAndServe(":5000", router)
}
httprouter's router.GET works only with httprouter.Handle type. Use the Handler method with http.Handler:
router.Handler("GET", "/", commonHandlers.ThenFunc(final))
I'd like to use httprouter with muxchain while keeping route parameters like /:user/.
Take the following example:
func log(res http.ResponseWriter, req *http.Request) {
fmt.Println("some logger")
}
func index(res http.ResponseWriter, req *http.Request) {
fmt.Fprintf(res, "Hi there, I love %s!", req.URL.Path[1:])
}
func main() {
logHandler := http.HandlerFunc(log)
indexHandler := http.HandlerFunc(index)
chain := muxchain.ChainHandlers(logHandler, indexHandler)
router := httprouter.New()
router.Handler("GET", "/:user", chain)
http.ListenAndServe(":8080", router)
}
When I visit http://localhost:8080/john I obviously don't have access to ps httprouter.Params
That's because httprouter needs to see type httprouter.Handle but the function is called with type http.Handler.
Is there any way to use both packages together? The HttpRouter GitHub repo says
The only disadvantage is, that no parameter values can be retrieved when a http.Handler or http.HandlerFunc is used, since there is no efficient way to pass the values with the existing function parameters.
If you strongly want to use that packages, you can try to do something like that:
package main
import (
"fmt"
"github.com/gorilla/context"
"github.com/julienschmidt/httprouter"
"github.com/stephens2424/muxchain"
"net/http"
)
func log(res http.ResponseWriter, req *http.Request) {
fmt.Printf("some logger")
}
func index(res http.ResponseWriter, req *http.Request) {
p := context.Get(req, "params").(httprouter.Params)
fmt.Fprintf(res, "Hi there, I love %s!", p.ByName("user"))
}
func MyContextHandler(h http.Handler) httprouter.Handle {
return func(res http.ResponseWriter, req *http.Request, p httprouter.Params) {
context.Set(req, "params", p)
h.ServeHTTP(res, req)
}
}
func main() {
logHandler := http.HandlerFunc(log)
indexHandler := http.HandlerFunc(index)
chain := muxchain.ChainHandlers(logHandler, indexHandler)
router := httprouter.New()
router.GET("/:user", MyContextHandler(chain))
http.ListenAndServe(":8080", router)
}
You would have to patch muxchain to accept httprouter.Handle, but it's rather simple to create your own chain handler, for example:
func chain(funcs ...interface{}) httprouter.Handle {
return func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
for _, h := range funcs {
switch h := h.(type) {
case httprouter.Handle:
h(w, r, p)
case http.Handler:
h.ServeHTTP(w, r)
case func(http.ResponseWriter, *http.Request):
h(w, r)
default:
panic("wth")
}
}
}
}
playground