Go 语言 net/http模块的完整方法详解及示例

以下是 Go 语言 net/http 模块的完整方法详解及示例，涵盖所有核心功能：

一、常量

常见的HTTP方法

IANA注册的HTTP状态代码

二、变量

HTTP 服务器使用的错误。

三.、HTTP 服务器功能方法

3.1 创建基本服务器

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)
}

3.2 路由处理

http.HandleFunc

http.HandleFunc("/greet", func(w http.ResponseWriter, r *http.Request) {
	name := r.URL.Query().Get("name")
	if name == "" {
		name = "Guest"
	}
	fmt.Fprintf(w, "Hello, %s!", name)
})

http.Handle (使用自定义处理器)

type greetingHandler struct{}

func (h *greetingHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "Welcome to the greeting page!")
}

func main() {
	http.Handle("/greeting", &greetingHandler{})
	http.ListenAndServe(":8080", nil)
}

3.3 使用 ServeMux 进行多路复用

func main() {
	mux := http.NewServeMux()
	
	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "Home Page")
	})
	
	mux.HandleFunc("/about", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "About Page")
	})
	
	http.ListenAndServe(":8080", mux)
}

3.4 中间件模式

func loggingMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		fmt.Printf("%s %s\n", r.Method, r.URL.Path)
		next.ServeHTTP(w, r)
	})
}

func main() {
	mux := http.NewServeMux()
	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "Home Page")
	})
	
	http.ListenAndServe(":8080", loggingMiddleware(mux))
}

3.5 文件服务器

func main() {
	// 静态文件服务
	fs := http.FileServer(http.Dir("static/"))
	http.Handle("/static/", http.StripPrefix("/static/", fs))
	
	http.ListenAndServe(":8080", nil)
}

四、 HTTP 客户端功能

4.1 发送 GET 请求

func main() {
	resp, err := http.Get("https://api.example.com/data")
	if err != nil {
		fmt.Println("Error:", err)
		return
	}
	defer resp.Body.Close()
	
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		fmt.Println("Error reading response:", err)
		return
	}
	
	fmt.Println(string(body))
}

4.2 发送 POST 请求

func main() {
	payload := strings.NewReader(`{"name":"John","age":30}`)
	resp, err := http.Post(
		"https://api.example.com/users",
		"application/json",
		payload,
	)
	if err != nil {
		fmt.Println("Error:", err)
		return
	}
	defer resp.Body.Close()
	
	// 处理响应...
}

4.3 自定义请求 (使用 http.NewRequest)

func main() {
	payload := strings.NewReader(`{"query":"search term"}`)
	
	req, err := http.NewRequest(
		"POST",
		"https://api.example.com/search",
		payload,
	)
	if err != nil {
		fmt.Println("Error creating request:", err)
		return
	}
	
	req.Header.Add("Content-Type", "application/json")
	req.Header.Add("Authorization", "Bearer abc123")
	
	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		fmt.Println("Error sending request:", err)
		return
	}
	defer resp.Body.Close()
	
	// 处理响应...
}

4.4 处理 JSON 响应

type User struct {
	ID    int    `json:"id"`
	Name  string `json:"name"`
	Email string `json:"email"`
}

func main() {
	resp, err := http.Get("https://api.example.com/users/1")
	if err != nil {
		fmt.Println("Error:", err)
		return
	}
	defer resp.Body.Close()
	
	var user User
	if err := json.NewDecoder(resp.Body).Decode(&user); err != nil {
		fmt.Println("Error decoding JSON:", err)
		return
	}
	
	fmt.Printf("User: %+v\n", user)
}

五、 高级功能

5.1 设置超时

func main() {
	client := &http.Client{
		Timeout: 10 * time.Second,
	}
	
	resp, err := client.Get("https://api.example.com/slow-endpoint")
	if err != nil {
		fmt.Println("Error:", err)
		return
	}
	defer resp.Body.Close()
	
	// 处理响应...
}

5.2 处理 Cookie

服务器设置 Cookie

func setCookieHandler(w http.ResponseWriter, r *http.Request) {
	cookie := &http.Cookie{
		Name:  "session_id",
		Value: "abc123",
		Path:  "/",
		MaxAge: 3600,
	}
	http.SetCookie(w, cookie)
	fmt.Fprintf(w, "Cookie set!")
}

客户端发送 Cookie

func main() {
	req, err := http.NewRequest("GET", "https://api.example.com/protected", nil)
	if err != nil {
		fmt.Println("Error:", err)
		return
	}
	
	cookie := &http.Cookie{
		Name:  "session_id",
		Value: "abc123",
	}
	req.AddCookie(cookie)
	
	client := &http.Client{}
	resp, err := client.Do(req)
	// 处理响应...
}

5.3 HTTPS 服务器

func main() {
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "Secure Hello World!")
	})
	
	err := http.ListenAndServeTLS(
		":443",
		"server.crt",
		"server.key",
		nil,
	)
	if err != nil {
		fmt.Println("Error starting server:", err)
	}
}

5.4 处理文件上传

func uploadHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}
	
	// 解析 multipart 表单，限制上传大小为 10MB
	err := r.ParseMultipartForm(10 << 20)
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	
	file, handler, err := r.FormFile("myFile")
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	defer file.Close()
	
	// 创建目标文件
	dst, err := os.Create(handler.Filename)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	defer dst.Close()
	
	// 复制文件内容
	if _, err := io.Copy(dst, file); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	
	fmt.Fprintf(w, "File uploaded successfully: %s", handler.Filename)
}

func main() {
	http.HandleFunc("/upload", uploadHandler)
	http.ListenAndServe(":8080", nil)
}

六、 重要类型和接口

6.1 http.ResponseWriter

用于构造 HTTP 响应，主要方法：

func handler(w http.ResponseWriter, r *http.Request) {
	// 设置状态码
	w.WriteHeader(http.StatusOK)
	
	// 设置响应头
	w.Header().Set("Content-Type", "application/json")
	w.Header().Add("X-Custom-Header", "value")
	
	// 写入响应体
	fmt.Fprintf(w, `{"status":"ok"}`)
}

6.2 http.Request

包含客户端请求的所有信息：

func handler(w http.ResponseWriter, r *http.Request) {
	// 请求方法
	method := r.Method
	
	// URL 信息
	path := r.URL.Path
	query := r.URL.Query().Get("param")
	
	// 请求头
	contentType := r.Header.Get("Content-Type")
	
	// 请求体
	body, err := io.ReadAll(r.Body)
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	
	// 表单数据
	formValue := r.FormValue("key")
	
	// 打印一些信息
	fmt.Printf("Method: %s, Path: %s, Query: %s\n", method, path, query)
	fmt.Printf("Content-Type: %s, Body: %s, FormValue: %s\n", contentType, body, formValue)
}

七、 实用工具函数

7.1 http.StripPrefix

func main() {
	// 将 /static/ 前缀去掉后再查找文件
	http.Handle("/static/", http.StripPrefix("/static/", http.FileServer(http.Dir("assets"))))
	http.ListenAndServe(":8080", nil)
}

7.2 http.Redirect

func redirectHandler(w http.ResponseWriter, r *http.Request) {
	http.Redirect(w, r, "https://example.com/new-location", http.StatusMovedPermanently)
}

7.3 http.NotFound

func handler(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/valid-path" {
		http.NotFound(w, r)
		return
	}
	fmt.Fprintf(w, "Valid path")
}

总结

net/http 包提供了构建 HTTP 客户端和服务器的完整工具集。通过上面的示例，我们可以看到：

1. 创建 HTTP 服务器非常简单，只需几行代码
2. 提供了灵活的路由处理机制
3. 支持中间件模式，方便扩展功能
4. 客户端 API 简洁但功能强大
5. 内置支持 HTTPS、文件上传、Cookie 等常见功能

对于更高级的需求，可以结合第三方路由库（如 gorilla/mux）或框架（如 Gin、Echo）使用，但标准库的 net/http 已经能够满足大多数基本需求。