Golang自建HTTP中间件

自建Http中间件

* 以类型形式
* 以函数形式
* 追加响应内容
* 自定义响应

以类型形式：

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)
}

以函数形式：

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)
}

自定义响应： net/http/httptest：响应请求时先进记录，不直接响应客户端，在彻底自定义时，还没准备好响应给客户端，先将请求虚拟记录下来，没有真正的相应出去，都在一个记录过程中，在彻底处理完后，在将响应一整套的响应给客户。

package main

//追加响应，传入handler 提示通过中间件处理
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)
}