go1.16新增的embed.FS - Wed, Apr 7, 2021

go1.16新增的embed.FS

1. 概述

go1.16中加入了内置的bindata，比原先的bindata包小了好多。

2. bindata的使用

将前端编译出来的文件打包成go

yarn build:prod
go-bindata-assetfs -pkg middlewares -nocompress=false dist/...

将前端go代码插入到http服务中

// Dashboard default url host:port or host:port/dashboard or host:port/dashboard/
func Dashboard(handler http.Handler) http.Handler {
	// return http.FileServer(assetFS())
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/dashboard" || r.URL.Path == "/" {
			http.Redirect(w, r, "/dashboard/", http.StatusFound)
			return
		}
		// Serving ./dashboard/
		if strings.Index(r.URL.Path, "/dashboard/") == 0 {
			http.StripPrefix("/dashboard/", http.FileServer(assetFS())).ServeHTTP(w, r)
			return
		}
		handler.ServeHTTP(w, r)
	})
}

bindata.go是用字符串存储二进制文件，会比原有的文件还要大。插入go编译生成的可执行文件中，会使执行文件显著增大。

3. embed.FS

目录结构

ui
├── dist
│   ├── favicon.ico
│   ├── index.html
│   └── static
│       ├── css
│       │   ├── app.bbbfe7a4.css
│       │   ├── chunk-9305baa0.2bcd27a6.css
│       ├── fonts
│       │   ├── element-icons.535877f5.woff
│       ├── img
│       │   ├── 404.a57b6f31.png
│       │   ├── 404_cloud.0f4bc32b.png
│       ├── js
│       │   ├── app.07035864.js
│       │   ├── chunk-0999b2fb.e2e2e3d4.js
│       └── swagger
│           └── swagger.yaml
└── ui.go

ui.go

package ui

import "embed"

//go:embed dist
var WebUI embed.FS

ui.go会把文件夹打包到WebUI变量中，注意WebUI是包含dist文件夹，后续操作需要去掉文件夹。

将前端go代码插入到http服务中。与bindata相比基本变化不大，多了Sub文件夹dist的操作。

// UI default url host:port or host:port/ui or host:port/ui/
func UI(handler http.Handler) http.Handler {
	// return http.FileServer(assetFS())
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/dashboard" || r.URL.Path == "/" {
			http.Redirect(w, r, "/dashboard/", http.StatusFound)
			return
		}
		// Serving ./dashboard/
		if strings.Index(r.URL.Path, "/dashboard/") == 0 {
			fsys, err := fs.Sub(ui.WebUI, "dist")
			if err != nil {
				http.Error(w, err.Error(), http.StatusNotFound)
				return
			}
			http.StripPrefix("/dashboard/", http.FileServer(http.FS(fsys))).ServeHTTP(w, r)
			return
		}
		handler.ServeHTTP(w, r)
	})
}