[Golang] 利用 net/http 寫Web Server (一) -- static files + template
Static file server
例如我有一包寫好的html/css/js, 叫做doc, 資料結構如下:
doc
├── css
│ └── main.css
└── index.html
main.go:
package main
import (
"log"
"net/http"
)
func main() {
handler:= http.FileServer(http.Dir("./doc"))
if err := http.ListenAndServe(":8080", handler); err != nil {
log.Fatal("ListenAndServe:", err)
}
}
打開http:localhost:8080就可以見到 doc/index.html的畫面。
Hello (from template)
$ mkdir templates
$ touch temlpates/Hello.html
Hello.html:
<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="UTF-8">
<title>Hello (from template)</title>
</head>
<body>
<h1>Hello!</h1>
</body>
</html>
main.go:
package main
import (
"html/template"
"log"
"net/http"
"path"
)
func handler(w http.ResponseWriter, r *http.Request) {
t := template.Must(template.ParseFiles(path.Join("templates", "Hello.html")))
t.Execute(w, nil)
}
func main() {
http.HandleFunc("/", handler)
if err := http.ListenAndServe(":8080", nil); err != nil {
log.Fatal("ListenAndServe:", err)
}
}
func Must(t *Template, err error) *Template就是一個helper function用來傳回Template用, 如果有錯就panic錯誤出來, 通常用來初始化template, func ParseFiles(filenames ...string) (*Template, error) 建立一個新的Template, 並且從所給的檔案裏面解析樣板。
Serve static file with template
我們把static資料夾, 當作是存放static files的根目錄:
$ mkdir -pv static/css static/js
$ touch static/css/main.cs static/js/main.js
main.css:
body {
color: #e91e63;
}
main.js:
function hello(){
alert('Hello again!');
}
修改templates/Hello.html加入相關 link:
<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="UTF-8">
<title>Hello (from template)</title>
<link rel="stylesheet" href="/static/css/main.css">
<script src="/static/js/main.js"></script>
</head>
<body>
<h1>Hello! (from template)</h1>
</body>
</html>
打開chrome devtool會告知:
...
Resource interpreted as Stylesheet but transferred with MIME type text/html
如果我們沒有指定對應css, js的URL handler, golang的net/http library就會把該路徑的回應都傳回text。Css, JavaScript檔案均為static file, 需要增加file server來處理, 修改main.go:
package main
import (
"html/template"
"log"
"net/http"
"path"
)
func handler(w http.ResponseWriter, r *http.Request) {
t := template.Must(template.ParseFiles(path.Join("templates", "Hello.html")))
t.Execute(w, nil)
}
func main() {
fs := http.FileServer(http.Dir("static"))
http.Handle("/static/", http.StripPrefix("/static/", fs))
http.HandleFunc("/", handler)
if err := http.ListenAndServe(":8080", nil); err != nil {
log.Fatal("ListenAndServe:", err)
}
}
就可正確得到預期的結果:
StripPrefix會傳回一個移除所給prefix的handler, 例如這裡如果我們的request是/static/css/main.css, 那麼StripPrefix就會刪掉/static/變成/css/main.css, 然後將修改過後的request傳給由http.FileServer()所傳回來的handler。
這裡我們的FileServer所指定的static為static files的根目錄。那我們要的/css/main.css的確在我們的static目錄裏面, 這樣就會得到我們要的結果。
錯誤處理
在handler加上一些錯誤處理, URL pattern只允許"/", method只允許"GET":
func handler(w http.ResponseWriter, r *http.Request) {
if r.URL.Path != "/" {
http.Error(w, "Not found", http.StatusNotFound)
return
}
if r.Method != "GET" {
http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
return
}
t := template.Must(template.ParseFiles(path.Join("templates", "Hello.html")))
t.Execute(w, nil)
}
More
stackoverflow - why do i need to use http stripprefix to access my static files
stackoverflow- how to render multipe templates in golang