Golang自建HTTP中間件

自建Http中間件

* 以類型形式
* 以函數形式
* 追加響應內容
* 自定義響應

以類型形式：

package main

import (
	"net/http"
)

type SingleHost struct {
	handler     http.Handler
	allowedHost string
}

func (this *SingleHost) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if r.Host == this.allowedHost {
		this.handler.ServeHTTP(w, r)
	} else {
		w.WriteHeader(403)
	}
}

func myHandler(w http.ResponseWriter, r *http.Request) {
	w.Write([]byte("hello world!"))
}

func main() {
	single := &SingleHost{
		handler:     http.HandlerFunc(myHandler),
		allowedHost: "baidu.com",
	}
	http.ListenAndServe(":8080", single)
}

以函數形式：

package main

import (
	"net/http"
)

func SingleHost(handler http.Handler, allowedHost string) http.Handler {
	fn := func(w http.ResponseWriter, r *http.Request) {
		if r.Host == r.allowedHost {
			handler.ServeHTTP(w, r)
		} else {
			w.WriteHeader(403)
		}
	}
	return http.HandlerFunc(fn)
}

func myHandler(w http.ResponseWriter,r *http.Request){
	w.Write([]byte("hello world!"))
}

func main(){
	single:=SingleHost(http.HandlerFunc(myHandler),"localhost:8080")
	http.ListenAndServe(":8080",single)
}

自定義響應： net/http/httptest：響應請求時先進記錄，不直接響應客戶端，在徹底自定義時，還沒準備好響應給客戶端，先將請求虛擬記錄下來，沒有真正的相應出去，都在一個記錄過程中，在徹底處理完後，在將響應一整套的響應給客戶。

package main

//追加響應，傳入handler 提示通過中間件處理
import (
	"net/http"
)

type AppendHiddleware struct{
	handler http.Handler
}

func (this *AppendHiddleware)ServeHTTP(w http.ResponseWriter,r *http.Request){

	if r.Host=="ccc"{
		this.handler.ServeHTTP(w,r)
		w.Write([]byte("Hey,this is middleware"))
	}else{
		w.Write([]byte("no host"))
	}
	
}

func myHandle(w http.ResponseWriter,r *http.Request){
	w.Write([]byte("hello myHandle!"))
}

func main(){
	mid:=&AppendHiddleware{http.HandlerFunc(myHandle)}

	http.ListenAndServe(":8080",mid)
}