cookie的使用

package main

import (
   "fmt"
   "net/http"
   "net/url"
)

func main() {
   // ========== 设置cookie『浏览器访问http://localhost:8080/SetCookie』 ========== //
   http.HandleFunc("/SetCookie", func(writer http.ResponseWriter, request *http.Request) {
      cookie := http.Cookie{
         Name:  "name",
         Value: url.QueryEscape("张三"), // 重要提醒：中文要进行编码处理
      }
      http.SetCookie(writer, &cookie)

      fmt.Println("设置cookie成功") // 设置cookie成功
   })

   // ========== 获取cookie『浏览器访问http://localhost:8080/GetCookie』 ========== //
   http.HandleFunc("/GetCookie", func(writer http.ResponseWriter, request *http.Request) {
      cookie, err := request.Cookie("name")
      if err == nil {
         value, _ := url.QueryUnescape(cookie.Value) // 由于设置cookie时进行了编码，故获取时要解码
         fmt.Printf("获取cookie成功，值为：%+v \n", value)   // 获取cookie成功，值为：张三
      } else {
         fmt.Printf("获取cookie失败：%+v \n", err.Error())
      }
   })

   // ========== 删除cookie『浏览器访问http://localhost:8080/DelCookie』 ========== //
   http.HandleFunc("/DelCookie", func(writer http.ResponseWriter, request *http.Request) {
      cookie := http.Cookie{
         Name:   "name",
         Value:  "",
         MaxAge: -1, // 重要说明：将MaxAge属性设为负数即可删除cookie
      }
      http.SetCookie(writer, &cookie)

      fmt.Println("删除cookie成功") // 删除cookie成功
   })

   _ = http.ListenAndServe(":8080", nil)
}

// ========== 总结 ==========//
// 1、调用http.SetCookie()并不是立即往客户端浏览器写cookie，而是随着服务器向客户端返回响应后才写，所以
//    调用http.SetCookie()设置cookie后立即调用request.Cookie()获取cookie是获取不到的。
// 2、调用request.Cookie()获取cookie，若cookie不存在，则err为非nil，错误信息为“http: named cookie not present”。