Go 语言 net/http 包使用之HTTP 服务器、客户端与中间件详解

package main
import (
    "fmt"
    "net/http"
)
func helloHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hello, World!")
}
func main() {
    http.HandleFunc("/hello", helloHandler)
    fmt.Println("Server starting on port 8080...")
    http.ListenAndServe(":8080", nil)
}

func helloHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hello, World!")
}
http.HandleFunc("/hello", helloHandler)

type CounterHandler struct {
    count int
}
func (h *CounterHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    h.count++
    fmt.Fprintf(w, "Visitor count: %d", h.count)
}
handler := &CounterHandler{}
http.Handle("/counter", handler)

mux := http.NewServeMux()
mux.HandleFunc("/products/", productsHandler)
mux.HandleFunc("/articles/", articlesHandler)
mux.HandleFunc("/", indexHandler)

resp, err := http.Get("https://example.com")
if err != nil {
    // 处理错误
}
defer resp.Body.Close()
body, err := io.ReadAll(resp.Body)
if err != nil {
    // 处理错误
}
fmt.Println(string(body))

data := url.Values{}
data.Set("key", "value")
resp, err := http.PostForm("https://example.com/form", data)
if err != nil {
    // 处理错误
}
defer resp.Body.Close()
// 处理响应...

req, err := http.NewRequest("GET", "https://example.com", nil)
if err != nil {
    // 处理错误
}
req.Header.Add("Authorization", "Bearer token123")
req.Header.Add("Content-Type", "application/json")
client := &http.Client{
    Timeout: time.Second * 10,
}
resp, err := client.Do(req)
if err != nil {
    // 处理错误
}
defer resp.Body.Close()
// 处理响应...

func loggingMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        start := time.Now()
        // 调用下一个处理器
        next.ServeHTTP(w, r)
        // 记录请求日志
        log.Printf(
            "%s %s %s %v",
            r.Method,
            r.URL.Path,
            r.RemoteAddr,
            time.Since(start),
        )
    })
}

func authMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        if !isAuthenticated(r) {
            http.Error(w, "Unauthorized", http.StatusUnauthorized)
            return
        }
        next.ServeHTTP(w, r)
    })
}
func main() {
    mux := http.NewServeMux()
    mux.HandleFunc("/secure", secureHandler)
    // 构建中间件链
    handler := loggingMiddleware(authMiddleware(mux))
    http.ListenAndServe(":8080", handler)
}

func requestIDMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // 生成唯一请求ID
        requestID := uuid.New().String()
        // 创建新上下文并存储请求ID
        ctx := context.WithValue(r.Context(), "requestID", requestID)
        // 设置响应头
        w.Header().Set("X-Request-ID", requestID)
        // 使用新上下文继续处理
        next.ServeHTTP(w, r.WithContext(ctx))
    })
}
// 在处理器中获取请求ID
func handler(w http.ResponseWriter, r *http.Request) {
    requestID := r.Context().Value("requestID").(string)
    fmt.Fprintf(w, "Request ID: %s", requestID)
}