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http_middleware.go
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http_middleware.go
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package main
import (
"fmt"
"log"
"net/http"
"time"
)
type Middleware func(http.HandlerFunc) http.HandlerFunc
// Logging logs all requests with its path and the time it took to process
func Logging() Middleware {
// Create a new Middleware
return func(f http.HandlerFunc) http.HandlerFunc {
// Define the http.HandlerFunc
return func(w http.ResponseWriter, r *http.Request) {
// Do middleware things
start := time.Now()
defer func() { log.Println(r.URL.Path, time.Since(start)) }()
// Call the next middleware/handler in chain
f(w, r)
}
}
}
// Method ensures that url can only be requested with a specific method, else returns a 400 Bad Request
func Method(m string) Middleware {
// Create a new Middleware
return func(f http.HandlerFunc) http.HandlerFunc {
// Define the http.HandlerFunc
return func(w http.ResponseWriter, r *http.Request) {
// Do middleware things
if r.Method != m {
http.Error(w, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
return
}
// Call the next middleware/handler in chain
f(w, r)
}
}
}
// Chain applies middlewares to a http.HandlerFunc
func Chain(f http.HandlerFunc, middlewares ...Middleware) http.HandlerFunc {
for _, m := range middlewares {
f = m(f)
}
return f
}
func Hello(w http.ResponseWriter, r *http.Request) {
fmt.Fprintln(w, "hello world")
}
/*
A middleware in itself simply takes a http.HandlerFunc as one of its parameters, wraps it and returns a new http.HandlerFunc for the server to call.
Here we define a new type Middleware which makes it eventually easier to chain multiple middlewares together.
This idea is inspired by Mat Ryers’ talk about Building APIs. You can find a more detailed explaination including the talk here.
https://gowebexamples.com/advanced-middleware/
*/
func main() {
http.HandleFunc("/", Chain(Hello, Method("GET"), Logging()))
err := http.ListenAndServe(":8080", nil)
if err != nil {
panic(fmt.Sprintf("ERROR when ListenAndServe : %v", err))
}
}