用Golang实现简易URL缩短教程

package main

import (
    "encoding/json"
    "fmt"
    "math/rand"
    "net/http"
    "strings"
    "time"
)

// 存储映射：短码 -> 原始 URL
var urlStore = make(map[string]string)

// 字符集用于生成短码
const shortChars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
const shortLength = 6

// 生成唯一的短码
func generateShortCode() string {
    rand.New(rand.NewSource(time.Now().UnixNano()))
    b := make([]byte, shortLength)
    for i := range b {
        b[i] = shortChars[rand.Intn(len(shortChars))]
    }
    return string(b)
}

// 创建短链接
func shortenHandler(w http.ResponseWriter, r *http.Request) {
    if r.Method != "POST" {
        http.Error(w, "只支持 POST", http.StatusMethodNotAllowed)
        return
    }

    type request struct {
        URL string `json:"url"`
    }

    var req request
    err := json.NewDecoder(r.Body).Decode(&req)
    if err != nil || req.URL == "" {
        http.Error(w, "无效的请求体", http.StatusBadRequest)
        return
    }

    // 确保 URL 以 http 开头
    if !strings.HasPrefix(req.URL, "http://") && !strings.HasPrefix(req.URL, "https://") {
        req.URL = "http://" + req.URL
    }

    // 生成短码（简单起见，不检查重复，实际应用需循环检查）
    var shortCode string
    for {
        shortCode = generateShortCode()
        if _, exists := urlStore[shortCode]; !exists {
            break
        }
    }

    urlStore[shortCode] = req.URL

    // 返回短链接
    result := map[string]string{
        "short_url": fmt.Sprintf("http://localhost:8080/%s", shortCode),
    }
    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(result)
}

// 重定向到原始 URL
func redirectHandler(w http.ResponseWriter, r *http.Request) {
    path := strings.TrimPrefix(r.URL.Path, "/")
    if path == "" {
        http.Error(w, "请输入短码", http.StatusBadRequest)
        return
    }

    originalURL, exists := urlStore[path]
    if !exists {
        http.Error(w, "短码不存在", http.StatusNotFound)
        return
    }

    http.Redirect(w, r, originalURL, http.StatusFound)
}

func main() {
    http.HandleFunc("/shorten", shortenHandler)
    http.HandleFunc("/", redirectHandler)

    fmt.Println("服务启动在 http://localhost:8080")
    http.ListenAndServe(":8080", nil)
}