I have a function need to be tested, which looks like this:
func parmHandler(w http.ResponseWriter, r *http.Request) {
...
data, err = backenddb_call(r *http.Request)
...
return
}
function backenddb_call(r *http.Request) (data []Data, err error){
parm := r.URL.Query().Get(parm)
//Get Data from DB for parm
...
return
}
In this HTTP handler case, I cannot modify the parmHandler arguments and add a helper interface argument to help with mocking. How can I mock backenddb_call to return different responses?
You could have a function which returns your handler, which you pass the backenddb_call as an argument to:
https://play.golang.org/p/aSMxeEgJL8U
func GetHandler(fn func (r *http.Request) ([]Data, error)) http.Handler {
return http.HandlerFunc(func (w http.ResponseWriter, r *http.Request) {
data, err := fn(r)
fmt.Println(data, err)
})
}
Then, when you create it:
http.HandleFunc("/test", GetHandler(backenddb_call))
and to test it you can just pass in a different call:
GetHandler(func (r *http.Request) ([]Data, error) {
fmt.Println("Mock")
return []Data{"This", "Is", "A", "Fake", "Response"}, nil
})
Related
Let say I have a function that handles request body in general
func GetReqBody(r *http.Request) (interface {}, error){
var data interface{}
decorder := json.NewDecoder(r.Body)
decorder.DisallowUnknownFields()
err := decorder.Decode(&data)
return data, err
}
Then in the controller, I will have to do type assertion
func post(w http.ResponseWriter, r *http.Request) {
data, err := utils.GetReqBody(r)
//req.User is a struct
newUser, ok := data.(req.User)
// ...
}
Is it possible to encapsulate the type assertion login inside the GetReqBody function? To do that I will need to pass the struct into the function, yet as it is not a value I am unable to do so.
"Is it possible to encapsulate the type assertion login inside the GetReqBody function?" -- No, it's not possible, not in any useful way.
However you could simplify your code thus:
func GetReqBody(r *http.Request, data interface{}) error {
decorder := json.NewDecoder(r.Body)
decorder.DisallowUnknownFields()
return decorder.Decode(data)
}
func post(w http.ResponseWriter, r *http.Request) {
var newUser req.User
if err := utils.GetReqBody(r, &newUser); err != nil {
// handle err
}
// ...
}
I'm designing a router API and I'd like to be able to lookup a path by its function. Something like:
createUser := func(w http.ResponseWriter, r *http.Request) {
// create a user
}
createPost := func(w http.ResponseWriter, r *http.Request) {
// create a post
}
router.Post("/users", createUser)
router.Post("/posts", createPost)
fmt.Println(router.Lookup(createPost))
Here's a playground link: https://play.golang.org/p/ec6U0jJUbfx
This is surprisingly hard to do because you can't test for equality on a function or stick it as a key in a map. Is this even possible?
Are there any other workarounds I'm not thinking of? A reflect solution would be just fine.
You can create a server struct with a ServerHTTP method that handles all the request. When there is a request you can look up for an specific method by the path and function
Here is an example:
type Server struct {
routes []route
}
func (s *Server) handlerServer(db mydb.IDB, ctx context.Context) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
ctx := ServerContext{w, r, db, ctx}
for i := 0; i < len(s.routes); i++ {
currentRoute := s.routes[i]
if isValidMethod(currentRoute, r) {
err := currentRoute.h(&ctx)
if err != nil {
log.Fatal(err)
}
}
}
}
}
I hope this is helpful
I am using gorilla/mux I have this:
router.HandleFunc("/api/v1/register",h.makeRegisterNewUser(v)).Methods("POST")
and h.makeRegisterNewUser looks like:
func (h Handler) makeRegisterNewUser(v interface{}) http.HandlerFunc {
type RespBody = ...;
type ReqBody = ...
return func(w http.ResponseWriter, r *http.Request) {
decoder := json.NewDecoder(r.Body)
err := decoder.Decode(&ReqBody)
// ...
json.NewEncoder(w).Encode(RespBody{});
}
}
my question is - is there a way to return multiple http.HandlerFuncs from makeRegisterNewUser? Something like this:
router.HandleFunc("/api/v1/register",h.makeRegisterNewUser(v)).Methods("POST")
func (h Handler) makeRegisterNewUser(v interface{}) (http.HandlerFunc...) {
type RespBody = ...;
type ReqBody = ...
return func(w http.ResponseWriter, r *http.Request) {
// 1
}, func(w http.ResponseWriter, r *http.Request) {
// 2
}, func(w http.ResponseWriter, r *http.Request) {
// 3
}
}
I am not sure if middleware can be chained in Go like it does in Node.js Express.
You can chain multiple http.Handler using wrapper:
type Middleware struct {
next http.Handler
}
func (m Middleware) Wrap(handler http.Handler) http.Handler {
m.next = handler
return m
}
func (m Middleware) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// run your handler code here
// write error into w and return if you need to interrupt request execution
// call next handler
m.next.ServeHTTP(w, r)
}
Register chained wrappers and main handler:
h1 := Middleware{}
h2 := OtherMiddleware{}
router.Handle("/some_route", h1.Wrap(h2.Wrap(mainHandler))).Methods(http.MethodPost)
Request will execute h1, h2 and finally mainHandler.
For example, you can log request in h1, authorize in h2 and keep business logic in mainHandler.
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 would like to ask if we can create 'middleware' functions for Go http client? Example I want to add a log function, so every sent request will be logged, or add setAuthToken so the token will be added to each request's header.
You can use the Transport parameter in HTTP client to that effect, with a composition pattern, using the fact that:
http.Client.Transport defines the function that will handle all HTTP requests;
http.Client.Transport has interface type http.RoundTripper, and can thus be replaced with your own implementation;
For example:
package main
import (
"fmt"
"net/http"
)
// This type implements the http.RoundTripper interface
type LoggingRoundTripper struct {
Proxied http.RoundTripper
}
func (lrt LoggingRoundTripper) RoundTrip(req *http.Request) (res *http.Response, e error) {
// Do "before sending requests" actions here.
fmt.Printf("Sending request to %v\n", req.URL)
// Send the request, get the response (or the error)
res, e = lrt.Proxied.RoundTrip(req)
// Handle the result.
if (e != nil) {
fmt.Printf("Error: %v", e)
} else {
fmt.Printf("Received %v response\n", res.Status)
}
return
}
func main() {
httpClient := &http.Client{
Transport: LoggingRoundTripper{http.DefaultTransport},
}
httpClient.Get("https://example.com/")
}
Feel free to alter names as you wish, I did not think on them for very long.
I worked on a project that had similar requirement so I built a middleware pipeline library that allows setting multiple middleware to the http client. You can check it out here.
Using the library, you would solve this in the following way
type LoggingMiddleware struct{}
func (s LoggingMiddleware) Intercept(pipeline pipeline.Pipeline, req *http.Request) (*http.Response, error) {
body, _ := httputil.DumpRequest(req, true)
log.Println(fmt.Sprintf("%s", string(body)))
/*
If you want to perform an action based on the response, do the following
resp, err = pipeline.Next
// perform some action
return resp, err
*/
return pipeline.Next(req)
}
transport := pipeline.NewCustomTransport(&LoggingMiddleware{})
client := &http.Client{Transport: transport}
resp, err := client.Get("https://example.com")
if err != nil {
// handle err
}
fmt.Println(resp.Status)
I wrote a small tutorial/library to do just that https://github.com/HereMobilityDevelopers/mediary
Here is some basic usage example:
client := mediary.Init().AddInterceptors(dumpInterceptor).Build()
client.Get("https://golang.org")
func dumpInterceptor(req *http.Request, handler mediary.Handler) (*http.Response, error) {
if bytes, err := httputil.DumpRequestOut(req, true); err == nil {
fmt.Printf("%s", bytes)
//GET / HTTP/1.1
//Host: golang.org
//User-Agent: Go-http-client/1.1
//Accept-Encoding: gzip
}
return handler(req)
}
There is also an explanation here https://github.com/HereMobilityDevelopers/mediary/wiki/Reasoning
Good idea! Here is a simple implementation of HTTP service middleware in Go.
Usually a simple http service framework is to register a bunch of routes, and then call different logics to process them according to the routes.
But in fact, there may be some unified processing involving almost all routes, such as logs, permissions, and so on.
So it is a good idea to engage in intermediate preprocessing at this time.
Define a middleware unit:
package main
import (
"net/http"
)
// AdaptorHandle middleware func type
type AdaptorHandle func(w http.ResponseWriter, r *http.Request) (next bool, err error)
// MiddleWareAdaptor router middlewares mapped by url
type MiddleWareAdaptor struct {
URLs map[string][]AdaptorHandle
}
// MakeMiddleWareAdaptor make a middleware adaptor
func MakeMiddleWareAdaptor() *MiddleWareAdaptor {
mwa := &MiddleWareAdaptor{
URLs: make(map[string][]AdaptorHandle),
}
return mwa
}
// Regist regist a adaptor
func (mw *MiddleWareAdaptor) Regist(url string, Adaptor ...AdaptorHandle) {
for _, adp := range Adaptor {
mw.URLs[url] = append(mw.URLs[url], adp)
// mw.URLs[url] = adp
}
}
// Exec exec middleware adaptor funcs...
func (mw *MiddleWareAdaptor) Exec(url string, w http.ResponseWriter, r *http.Request) (bool, error) {
if adps, ok := mw.URLs[url]; ok {
for _, adp := range adps {
if next, err := adp(w, r); !next || (err != nil) {
return next, err
}
}
}
return true, nil
}
Then wrap the route processing function with a middleware entry:
func middlewareHandler(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
// before call handler
start := time.Now()
do, _ := mwa.Exec(r.URL.Path, w, r) // exec middleware
// call next handler
if do {
log.Println("middleware done. next...")
next.ServeHTTP(w, r)
} else {
log.Println("middleware done.break...")
}
// after call handle
log.Printf("Comleted %s in %v", r.URL.Path, time.Since(start))
})
}
mux.Handle("/", middlewareHandler(&uPlusRouterHandler{}))
type uPlusRouterHandler struct {
}
func (rh *uPlusRouterHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
...
}
Finally, register the middleware you need:
mwa = MakeMiddleWareAdaptor() // init middleware
mwa.Regist("/", testMWAfunc, testMWAfunc2) // regist middleware
...
func testMWAfunc(w http.ResponseWriter, r *http.Request) (bool, error) {
log.Println("I am Alice Middleware...")
log.Printf("Started %s %s", r.Method, r.URL.Path)
return true, nil
}
func testMWAfunc2(w http.ResponseWriter, r *http.Request) (bool, error) {
log.Println("I am Ben Middleware...")
return false, nil // return false,break follow-up actions.
}
This can be achieved using closure functions. It's probably more clear with an example:
package main
import (
"fmt"
"net/http"
)
func main() {
http.HandleFunc("/hello", logged(hello))
http.ListenAndServe(":3000", nil)
}
func logged(f func(http.ResponseWriter, *http.Request)) func(http.ResponseWriter, *http.Request) {
return func(w http.ResponseWriter, r *http.Request) {
fmt.Println("logging something")
f(w, r)
fmt.Println("finished handling request")
}
}
func hello(w http.ResponseWriter, r *http.Request) {
fmt.Fprintln(w, "<h1>Hello!</h1>")
}
credit goes to: http://www.calhoun.io/5-useful-ways-to-use-closures-in-go/