Golang原生http实现中间件

中间件（middleware）：常被用来做认证校验、审计等

• 大家常用的Iris、Gin等web框架，都包含了中间件逻辑。但有时我们引入该框架显得较为繁重，本文将介绍通过golang原生http来实现中间件操作。
• 全部代码：https://github.com/ziyifast/ziyifast-code_instruction/tree/main/middleware

1 定义http.Handler：具体中间件操作

①CORSMiddleware：允许跨域

// CORSMiddleware handles Cross-Origin Resource Sharing (CORS) responses.
func CORSMiddleware(next http.Handler) http.Handler {fmt.Println("cors middleware....")return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {if r.Method == "OPTIONS" {w.Header().Set("Access-Control-Allow-Origin", "*")w.Header().Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS, DELETE")//如果前后端需要传递自定义请求头，需要再Access-Control-Allow-Headers中匹配(Yi-Auth-Token)w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Accept, Yi-Auth-Token")w.WriteHeader(http.StatusOK)return}w.Header().Set("Access-Control-Allow-Origin", "*")w.Header().Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS, DELETE")w.Header().Set("Access-Control-Allow-Headers", "Content-Type,Accept,Yi-Auth-Token")//交给下一个中间件处理next.ServeHTTP(w, r)})
}

②AuthMiddleware：认证

// AuthMiddleware simulates a simple authentication middleware.
func AuthMiddleware(next http.Handler) http.Handler {return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {fmt.Println("auth middleware...")//store info in ctxtoken := r.Header.Get("Token")if len(token) != 0 {//TODO 1. check token 2. get userinfo from tokenuserID := "1"ctx := context.WithValue(r.Context(), "userID", userID)r = r.WithContext(ctx)}next.ServeHTTP(w, r)})
}

③AuditMiddleware：审计操作

// AuditMiddleware simulates an audit logging middleware.
func AuditMiddleware(next http.Handler) http.Handler {return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {fmt.Println("audit middleware...")next.ServeHTTP(w, r)})
}

④SmokeHandler：具体处理操作

// SmokeHandler returns the current time as a string.
func SmokeHandler(w http.ResponseWriter, r *http.Request) {fmt.Println("smoke handle....")_, err := w.Write([]byte(time.Now().String()))if err != nil {http.Error(w, "Internal Server Error", http.StatusInternalServerError)}
}

2 义中间件类型&定义中间件链

①type Middleware func(http.Handler) http.Handler：定义中间件

type Middleware func(http.Handler) http.Handler

②定义中间件链MiddlewareChain

// NewMiddlewareChain creates a new middleware chain with the given middlewares.
func NewMiddlewareChain(middlewares ...Middleware) Middleware {return func(handler http.Handler) http.Handler {for i := len(middlewares) - 1; i >= 0; i-- {handler = middlewares[i](handler)}return handler}
}

3 启动http服务

func RunAndServe() error {defer func() {if e := recover(); e != nil {fmt.Println("err=", e)}}()mux := http.NewServeMux()// Create middleware chains for routes.authMiddlewareChain := NewMiddlewareChain(CORSMiddleware, AuthMiddleware, AuditMiddleware)//noAuthMiddlewareChain := NewMiddlewareChain(CORSMiddleware)// Convert the middleware chain result to http.HandlerFunc.smokeHandlerWrapped := func(w http.ResponseWriter, r *http.Request) {authMiddlewareChain(http.HandlerFunc(SmokeHandler)).ServeHTTP(w, r)}mux.HandleFunc("/smoke", smokeHandlerWrapped)fmt.Printf("listening on http://localhost:%d\n", 9999)return http.ListenAndServe(":9999", mux)
}

4 测试

1. 启动后端

go run main.go

2. 浏览器访问http://localhost:9999/smoke

3. 后端日志打印

可以看到是最后才处理我们的业务Handler

全部代码

🚀：https://github.com/ziyifast/ziyifast-code_instruction/tree/main/middleware

package mainimport ("context""fmt""net/http""time"
)type Middleware func(http.Handler) http.Handler// CORSMiddleware handles Cross-Origin Resource Sharing (CORS) responses.
func CORSMiddleware(next http.Handler) http.Handler {fmt.Println("cors middleware....")return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {if r.Method == "OPTIONS" {w.Header().Set("Access-Control-Allow-Origin", "*")w.Header().Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS, DELETE")//如果前后端需要传递自定义请求头，需要再Access-Control-Allow-Headers中匹配(Yi-Auth-Token)w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Accept, Yi-Auth-Token")w.WriteHeader(http.StatusOK)return}w.Header().Set("Access-Control-Allow-Origin", "*")w.Header().Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS, DELETE")w.Header().Set("Access-Control-Allow-Headers", "Content-Type,Accept,Yi-Auth-Token")next.ServeHTTP(w, r)})
}// AuthMiddleware simulates a simple authentication middleware.
func AuthMiddleware(next http.Handler) http.Handler {return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {fmt.Println("auth middleware...")//store info in ctxtoken := r.Header.Get("Token")if len(token) != 0 {//TODO 1. check token 2. get userinfo from tokenuserID := "1"ctx := context.WithValue(r.Context(), "userID", userID)r = r.WithContext(ctx)}next.ServeHTTP(w, r)})
}// AuditMiddleware simulates an audit logging middleware.
func AuditMiddleware(next http.Handler) http.Handler {return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {fmt.Println("audit middleware...")next.ServeHTTP(w, r)})
}// SmokeHandler returns the current time as a string.
func SmokeHandler(w http.ResponseWriter, r *http.Request) {fmt.Println("smoke handle....")_, err := w.Write([]byte(time.Now().String()))if err != nil {http.Error(w, "Internal Server Error", http.StatusInternalServerError)}
}// NewMiddlewareChain creates a new middleware chain with the given middlewares.
func NewMiddlewareChain(middlewares ...Middleware) Middleware {return func(handler http.Handler) http.Handler {for i := len(middlewares) - 1; i >= 0; i-- {handler = middlewares[i](handler)}return handler}
}func RunAndServe() error {defer func() {if e := recover(); e != nil {fmt.Println("err=", e)}}()mux := http.NewServeMux()// Create middleware chains for routes.authMiddlewareChain := NewMiddlewareChain(CORSMiddleware, AuthMiddleware, AuditMiddleware)//noAuthMiddlewareChain := NewMiddlewareChain(CORSMiddleware)// Convert the middleware chain result to http.HandlerFunc.smokeHandlerWrapped := func(w http.ResponseWriter, r *http.Request) {authMiddlewareChain(http.HandlerFunc(SmokeHandler)).ServeHTTP(w, r)}mux.HandleFunc("/smoke", smokeHandlerWrapped)fmt.Printf("listening on http://localhost:%d\n", 9999)return http.ListenAndServe(":9999", mux)
}func main() {RunAndServe()
}