Golang Web编程的Get和Post请求发送与解析

          本文的是一篇入门文章，通过一个简单的例子介绍Golang的Web编程主要用到的技术。

          文章结构包括：

1. Client-Get 请求
   
2. Client-Post 请求
   
3. Server 处理 Get 和 Post 数据

          在数据的封装中，我们部分采用了json，因而本文也涉及到Golang中json的编码和解码。

一、Client-Get

package main

import (
        "fmt"
        "net/url"
        "net/http"
        "io/ioutil"
        "log"
)

func main() {
        u, _ := url.Parse("http://localhost:9001/xiaoyue")
        q := u.Query()
        q.Set("username", "user")
        q.Set("password", "passwd")
        u.RawQuery = q.Encode()
        res, err := http.Get(u.String());
        if err != nil { 
              log.Fatal(err) return 
        }
        result, err := ioutil.ReadAll(res.Body) 
        res.Body.Close() 
        if err != nil { 
              log.Fatal(err) return 
        } 
        fmt.Printf("%s", result)
} 

二、Client-Post

package main

import (
        "fmt"
        "net/url"
        "net/http"
        "io/ioutil"
        "log"
        "bytes"
        "encoding/json"
)

type Server struct {
        ServerName string
        ServerIP   string
}

type Serverslice struct {
        Servers []Server
        ServersID  string
}


func main() {

        var s Serverslice

        var newServer Server;
        newServer.ServerName = "Guangzhou_VPN";
        newServer.ServerIP = "127.0.0.1"       
        s.Servers = append(s.Servers, newServer)

        s.Servers = append(s.Servers, Server{ServerName: "Shanghai_VPN", ServerIP: "127.0.0.2"})
        s.Servers = append(s.Servers, Server{ServerName: "Beijing_VPN", ServerIP: "127.0.0.3"})
        
        s.ServersID = "team1"

        b, err := json.Marshal(s)
        if err != nil {
                fmt.Println("json err:", err)
        }

        body := bytes.NewBuffer([]byte(b))
        res,err := http.Post("http://localhost:9001/xiaoyue", "application/json;charset=utf-8", body)
        if err != nil {
                log.Fatal(err)
                return
        }
        result, err := ioutil.ReadAll(res.Body)
        res.Body.Close()
        if err != nil {
                log.Fatal(err)
                return
        }
        fmt.Printf("%s", result)
}

三、Server

package main

import (
        "fmt"
        "net/http"
        "strings"
        "html"
        "io/ioutil"
        "encoding/json"
)

type Server struct {
        ServerName string
        ServerIP   string
}

type Serverslice struct {
        Servers []Server
        ServersID  string
}

func main() {
        http.HandleFunc("/", handler) 
        http.ListenAndServe(":9001", nil)
}

func handler(w http.ResponseWriter, r *http.Request) { 
        r.ParseForm() //解析参数，默认是不会解析的 
        fmt.Fprintf(w, "Hi, I love you %s", html.EscapeString(r.URL.Path[1:]))
        if r.Method == "GET" {
                fmt.Println("method:", r.Method) //获取请求的方法 

                fmt.Println("username", r.Form["username"]) 
                fmt.Println("password", r.Form["password"]) 

                for k, v := range r.Form {
                        fmt.Print("key:", k, "; ")
                        fmt.Println("val:", strings.Join(v, ""))
                }
        } else if r.Method == "POST" {
                result, _:= ioutil.ReadAll(r.Body)
                r.Body.Close()
                fmt.Printf("%s\n", result)

                //未知类型的推荐处理方法

                var f interface{}
                json.Unmarshal(result, &f) 
                m := f.(map[string]interface{})
                for k, v := range m {
                        switch vv := v.(type) {
                                case string:
                                        fmt.Println(k, "is string", vv)
                                case int:
                                        fmt.Println(k, "is int", vv)
                                case float64:
                                        fmt.Println(k,"is float64",vv)
                                case []interface{}:
                                        fmt.Println(k, "is an array:")
                                        for i, u := range vv {
                                                fmt.Println(i, u)
                                        }
                                default:
                                        fmt.Println(k, "is of a type I don't know how to handle") 
                         }
                  }

                 //结构已知，解析到结构体

                 var s Serverslice;
                 json.Unmarshal([]byte(result), &s)

                 fmt.Println(s.ServersID);
  
                 for i:=0; i<len(s.Servers); i++ {
                         fmt.Println(s.Servers[i].ServerName)
                         fmt.Println(s.Servers[i].ServerIP)
                 }
        } 
}

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