go语言使用phantomjs提供截图服务
1. 什么是Phantomjs
PhantomJS是一个基于webkit的JavaScript API.它使用QtWebKit作为它核心浏览器的功能,使用webkit来编译解释执行JavaScript代码.任何您可以在基于webkit浏览器做的事情,它都能做到.它不仅是个隐形的浏览器,提供了诸如CSS选择器,支持Web标准,DOM操作,JSON,HTML5,Canvas,SVG等,同时也提供了处理文件I/O的操作,从而使您可以向操作系统读写文件等.PhantomJS的用处可谓非常广泛,诸如网络监测,网页截屏,无需浏览器的 Web 测试,页面访问自动化等.
2. 准备工作
- *unix系统安装phantomJS可执行文件,
phantomjs添加到系统环境变量 - 检验phantomjs安装是否成功,
在终端中运行$:phantomjs不报错,则安装成功 - 安装go package
github.com/benbjohnson/phantomjs,主要功能方便go调用phantomJS二进制文件命令
3. go调用phantomJS代码解析
3.1 defer函数捕捉panic
func main() {
defer func(){
err:= recover()
if err != nil {
println(err)
}
}()
var url = "https://www.163.com"
3.2 创建一个在golang里面phantomJS创建一个phanomJS进程
if err := phantomjs.DefaultProcess.Open(); err != nil {
panic(err)
os.Exit(1)
}
defer phantomjs.DefaultProcess.Close()
3.3 创建phantomJS page设置请求headers和view port
page, err := phantomjs.CreateWebPage()
if err != nil {
panic(err)
}
//set request headers 设置UserAgent为iPhone
requestHeader := http.Header{
"User-Agent" :[]string{"Mozilla/5.0 (iPhone; CPU iPhone OS 11_0 like Mac OS X) AppleWebKit/604.1.38 (KHTML, like Gecko) Version/11.0 Mobile/15A372 Safari/604.1"},
}
if err := page.SetCustomHeaders(requestHeader);err != nil {
panic(err)
}
// Setup the viewport and render the results view.
if err := page.SetViewportSize(640, 960); err != nil {
panic(err)
}
3.4 截图并输出png文件
// Open a URL.
if err := page.Open(url); err != nil {
panic(err)
}
if err := page.Render("hackernews4.png", "png", 50); err != nil {
panic(err)
}
}
3.5 完整代码 main.go
package main
import (
"github.com/benbjohnson/phantomjs"
"os"
"net/http"
)
//https://github.com/benbjohnson/phantomjs
func main() {
defer func(){
err:= recover()
if err != nil {
println(err)
}
}()
var url = "https://www.163.com"
// Start the process once.
if err := phantomjs.DefaultProcess.Open(); err != nil {
panic(err)
os.Exit(1)
}
defer phantomjs.DefaultProcess.Close()
page, err := phantomjs.CreateWebPage()
if err != nil {
panic(err)
}
//set request headers
requestHeader := http.Header{
"User-Agent" :[]string{"Mozilla/5.0 (iPhone; CPU iPhone OS 11_0 like Mac OS X) AppleWebKit/604.1.38 (KHTML, like Gecko) Version/11.0 Mobile/15A372 Safari/604.1"},
}
if err := page.SetCustomHeaders(requestHeader);err != nil {
panic(err)
}
// Setup the viewport and render the results view.
if err := page.SetViewportSize(640, 960); err != nil {
panic(err)
}
// Open a URL.
if err := page.Open(url); err != nil {
panic(err)
}
if err := page.Render("163_news_screen_shot.png", "png", 50); err != nil {
panic(err)
}}
4. 使用go标准库创建截图微服务
4.1 main.go完成代码
// example of HTTP server that uses the captcha package.
package main
import (
"encoding/json"
"fmt"
"log"
"net/http"
"os"
"github.com/benbjohnson/phantomjs"
)
const OutputDir = "screen_shot"
//ConfigJsonBody json request body.
type jsonBody struct {
Url string `json:"url"`
ViewportWidth int `json:"viewport_width"`
ViewportHeight int `json:"viewport_height"`
OutputFileName string `json:"output_file_name"`
OutputFileExt string `json:"output_file_ext"`
Quility int `json:"quility"`
OutputUri string `json:"output_uri"`
}
func screen_shot(w http.ResponseWriter, r *http.Request) {
//parse request parameters
//接收客户端发送来的请求参数json
decoder := json.NewDecoder(r.Body)
var postParameters jsonBody
err := decoder.Decode(&postParameters)
if err != nil {
log.Println(err)
}
defer r.Body.Close()
//截图网页
phantomjs_screen_shot(&postParameters)
//set json response
//设置json响应
w.Header().Set("Content-Type", "application/json; charset=utf-8")
body := map[string]interface{}{"code": 1, "data": postParameters, "msg": "success"}
json.NewEncoder(w).Encode(body)
}
func phantomjs_screen_shot(config *jsonBody) {
uri := fmt.Sprintf("%s/%s", OutputDir,config.OutputFileName)
config.OutputFileName = uri
config.OutputUri = uri
// Start the process once.
if err := phantomjs.DefaultProcess.Open(); err != nil {
panic(err)
os.Exit(1)
}
defer phantomjs.DefaultProcess.Close()
page, err := phantomjs.CreateWebPage()
if err != nil {
panic(err)
}
//set request headers
requestHeader := http.Header{
"User-Agent" :[]string{"Mozilla/5.0 (iPhone; CPU iPhone OS 11_0 like Mac OS X) AppleWebKit/604.1.38 (KHTML, like Gecko) Version/11.0 Mobile/15A372 Safari/604.1"},
}
if err := page.SetCustomHeaders(requestHeader);err != nil {
panic(err)
}
// Setup the viewport and render the results view.
if err := page.SetViewportSize(config.ViewportWidth, config.ViewportHeight); err != nil {
panic(err)
}
// Open a URL.
if err := page.Open(config.Url); err != nil {
panic(err)
}
if err := page.Render(config.OutputFileName, config.OutputFileExt, config.Quility); err != nil {
panic(err)
}
}
//start a net/http server
//启动golang net/http 服务器
func main() {
pathPrefix := "/"+OutputDir +"/"
staticDir := "./"+OutputDir
http.Handle(pathPrefix,http.StripPrefix(pathPrefix, http.FileServer(http.Dir(staticDir))))
//api for create captcha
http.HandleFunc("/api/shot", screen_shot)
fmt.Println("Server is at localhost:1122")
if err := http.ListenAndServe("localhost:1122", nil); err != nil {
log.Fatal(err)
}
}
4.2 postmanAPI接口
POST /api/shot HTTP/1.1
Host: localhost:1122
Content-Type: application/json
Cache-Control: no-cache
{
"url":"http://www.163.com",
"viewport_width":480,
"viewport_height":960,
"output_file_name":"awesome.jpg",
"output_file_ext":"jpg",
"quility":90
}
4.3 返回参数
{
"code": 1,
"data": {
"url": "http://www.163.com",
"viewport_width": 480,
"viewport_height": 960,
"output_file_name": "screen_shot/awesome.jpg",
"output_file_ext": "jpg",
"quility": 90,
"output_uri": "screen_shot/awesome.jpg"
},
"msg": "success"
}