1、HTTP服务

路由规则

• URL 分为两种，末尾是 /：表示⼀个⼦树，后⾯可以跟其他⼦路径； 末尾不
是 /，表示⼀个叶⼦，固定的路径
• 以/ 结尾的 URL 可以匹配它的任何⼦路径，⽐如 /images 会匹配 /images/
cute-cat.jpg
• 它采⽤最⻓匹配原则，如果有多个匹配，⼀定采⽤匹配路径最⻓的那个进⾏处
理• 如果没有找到任何匹配项，会返回 404 错误

package main

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

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        fmt.Fprintf(w, "Hello World!")
    })
    http.HandleFunc("/time/", func(w http.ResponseWriter, r *http.Request) {
        t := time.Now()
        timeStr := fmt.Sprintf("{\"time\": \"%s\"}", t)
        w.Write([]byte(timeStr))
    })

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

2、构建RESTful服务

// 国内源安装失败，切换成国外源才行
// go get github.com/julienschmidt/httprouter
package main

import (
    "fmt"
    "github.com/julienschmidt/httprouter"
    "log"
    "net/http"
)

func Index(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
    fmt.Fprint(w, "Welcome!\n")
}

func Hello(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
    fmt.Fprintf(w, "hello, %s!\n", ps.ByName("name"))
}

func main() {
    router := httprouter.New()
    router.GET("/", Index)
    router.GET("/hello/:name", Hello)

    log.Fatal(http.ListenAndServe(":8080", router))
}

3、⾯向资源的架构（Resource Oriented Architecture）

package main

import (
    "encoding/json"
    "fmt"
    "log"
    "net/http"

    "github.com/julienschmidt/httprouter"
)

type Employee struct {
    ID   string `json:"id"`
    Name string `json:"name"`
    Age  int    `json:"age"`
}

var employeeDB map[string]*Employee

func init() {
    employeeDB = map[string]*Employee{}
    employeeDB["Mike"] = &Employee{"e-1", "Mike", 35}
    employeeDB["Rose"] = &Employee{"e-2", "Rose", 45}
}

func Index(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
    fmt.Fprint(w, "Welcome!\n")
}

func GetEmployeeByName(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
    qName := ps.ByName("name")
    var (
        ok       bool
        info     *Employee
        infoJson []byte
        err      error
    )
    if info, ok = employeeDB[qName]; !ok {
        w.Write([]byte("{\"error\":\"Not Found\"}"))
        return
    }
    if infoJson, err = json.Marshal(info); err != nil {
        w.Write([]byte(fmt.Sprintf("{\"error\":,\"%s\"}", err)))
        return
    }

    w.Write(infoJson)
}

func main() {
    router := httprouter.New()
    router.GET("/", Index)
    router.GET("/employee/:name", GetEmployeeByName)

    log.Fatal(http.ListenAndServe(":8080", router))
}