Go爬虫

• Flag
• HTML解析
• chromedp
• godet
• gcd

Flag

xpath和css选择器

HeadlessBrowser

• https://github.com/go-rod/rod (opens new window)
• https://github.com/derekparker/delve (opens new window)
• https://github.com/mafredri/cdp (opens new window)
• 类BeautifulSoup https://github.com/anaskhan96/soup (opens new window)

HTML解析

• https://github.com/antchfx (opens new window) htmlquery使用xpath选择器
• https://github.com/PuerkitoBio/goquery (opens new window) goquery使用css选择器
• https://github.com/gocolly/colly (opens new window)
• https://github.com/go-predator/predator (opens new window)

chromedp

• https://github.com/chromedp (opens new window)

该组织下有以下项目

• https://github.com/chromedp/chromedp

https://godoc.org/github.com/chromedp/chromedp (opens new window)

• https://github.com/chromedp/cdproto-gen

生成用于Chrome DevTools (opens new window)协议的命令，事件和类型的Go代码

• https://github.com/chromedp/cdproto

包含针对Chrome DevTools (opens new window)协议域生成的命令，类型和事件

https://godoc.org/github.com/chromedp/cdproto (opens new window)

cdproto下有以下包

• github.com/chromedp/cdproto/cdp

cdp.TimeSinceEpoch(time.Now().Add(180 * 24 * time.Hour))

• github.com/chromedp/cdproto/network 网络处理

比如启用启用网络跟踪，现在将网络事件传递给客户端network.Enable()

• github.com/chromedp/cdproto/page chrome页面处理

比如设置下载page.SetDownloadBehavior(page.SetDownloadBehaviorBehaviorDeny)

• github.com/chromedp/cdproto/target 操作标签页 Target.createTarget (opens new window)

// 根据url新建浏览器标签页
tag := target.CreateTarget(url)
// 新建浏览器标签页ID创建上下文，方式一
ctx, cancel = chromedp.NewContext(ctx, chromedp.WithTargetID(target.ID(tag.BrowserContextID)))

// 根据上下文，返回targetID-打开的页面的ID。
tagId, err := tag.Do(ctx)
// 新建浏览器标签页ID创建上下文，方式二
ctx, cancel = chromedp.NewContext(ctx, chromedp.WithTargetID(tagId))

chromedp.Targets(ctx) 获取浏览器实例的标签页信息列表

chromedp能做什么

• 反爬虫js，例如有的网页后台js自动发送心跳包，浏览器里会自动运行，不需要我们自动处理

• 针对于前端页面的自动化测试

• 解决类似VueJS和SPA之类的渲染

• 解决网页的懒加载

• 网页截图和pdf导出，而不需要额外的去学习其他的库实现

• seo训练和刷点击量

• 执行javascript 代码

• 设置dom的标签属性

chromedp同Python的selenium,它是使用Chrome Debugging Protocol(简称cdp) 并且没有外部依赖 (如Selenium, PhantomJS等)

• golang headless browser包chromedp初探 (opens new window)
• go语言chromedp使用教程 (opens new window)

函数或变量	说明
(a *ExecAllocator) Allocate(ctx context.Context, opts ...BrowserOption) (*Browser, error)
(a *ExecAllocator) Wait()
(a *RemoteAllocator) Allocate(ctx context.Context, opts ...BrowserOption) (*Browser, error)
(a *RemoteAllocator) Wait()
(f ActionFunc) Do(ctx context.Context) error
(s *Selector) Do(ctx context.Context) error
(t Tasks) Do(ctx context.Context) error
After(f func(context.Context, ...*cdp.Node) error) QueryOption
AtLeast(n int) QueryOption
Attributes(sel interface{}, attributes *map[string]string, opts ...QueryOption) QueryAction
AttributesAll(sel interface{}, attributes *[]map[string]string, opts ...QueryOption) QueryAction
AttributeValue(sel interface{}, name string, value *string, ok *bool, opts ...QueryOption) QueryAction
Blur(sel interface{}, opts ...QueryOption) QueryAction
ByFunc(f func(context.Context, *cdp.Node) ([]cdp.NodeID, error)) QueryOption
ByID(s *Selector)	只id来选择元素
ByJSPath(s *Selector)
ByNodeID(s *Selector)	按节点ID选择元素
ByQuery(s *Selector)	根据document.querySelector的规则选择元素，返回单个节点
ByQueryAll(s *Selector)	根据document.querySelectorAll返回所有匹配的节点
BySearch(s *Selector)	如果不写，默认会使用这个选择器，类似devtools ctrl+f 搜索
Cancel(ctx context.Context) error
CaptureScreenshot(res *[]byte) Action
Clear(sel interface{}, opts ...QueryOption) QueryAction
Click(sel interface{}, opts ...QueryOption) QueryAction	触发点击事件
CombinedOutput(w io.Writer) ExecAllocatorOption
ComputedStyle(sel interface{}, style *[]*css.ComputedProperty, opts ...QueryOption) QueryAction
Dimensions(sel interface{}, model **dom.BoxModel, opts ...QueryOption) QueryAction
DisableGPU(a *ExecAllocator)	关闭gpu,服务器一般没有显卡
DoubleClick(sel interface{}, opts ...QueryOption) QueryAction
Env(vars ...string) ExecAllocatorOption	NAME=value形式的通用环境变量列表，用于传递到新的Chrome进程。
ExecPath(path string) ExecAllocatorOption
Flag(name string, value interface{}) ExecAllocatorOption
Focus(sel interface{}, opts ...QueryOption) QueryAction
FromContext(ctx context.Context) *Context
Headless(a *ExecAllocator)
InnerHTML(sel interface{}, html *string, opts ...QueryOption) QueryAction
JavascriptAttribute(sel interface{}, name string, res interface{}, opts ...QueryOption) QueryAction
ListenBrowser(ctx context.Context, fn func(ev interface{}))
ListenTarget(ctx context.Context, fn func(ev interface{}))
Location(urlstr *string) Action
MatchedStyle(sel interface{}, style **css.GetMatchedStylesForNodeReturns, opts ...QueryOption) QueryAction
Navigate(urlstr string) NavigateAction	设置url
NavigateBack() NavigateAction
NavigateForward() NavigateAction
NavigateToHistoryEntry(entryID int64) NavigateAction
NavigationEntries(currentIndex *int64, entries *[]*page.NavigationEntry) NavigateAction
NewContext(parent context.Context, opts ...ContextOption) (context.Context, context.CancelFunc)
NewExecAllocator(parent context.Context, opts ...ExecAllocatorOption) (context.Context, context.CancelFunc)
NewRemoteAllocator(parent context.Context, url string) (context.Context, context.CancelFunc)
NodeEnabled(s *Selector)
NoDefaultBrowserCheck(a *ExecAllocator)	禁用默认浏览器检查。
NodeIDs(sel interface{}, ids *[]cdp.NodeID, opts ...QueryOption) QueryAction
NodeNotPresent(s *Selector)
NodeNotVisible(s *Selector)
NodeReady(s *Selector)
Nodes(sel interface{}, nodes *[]*cdp.Node, opts ...QueryOption) QueryAction
NodeSelected(s *Selector)
NodeVisible(s *Selector)
NoFirstRun(a *ExecAllocator)	禁用第一次运行对话框的Chrome命令行选项
NoSandbox(a *ExecAllocator)	用于禁用沙箱的Chrome命令行选项
OuterHTML(sel interface{}, html *string, opts ...QueryOption) QueryAction	获取HTML源码
ProxyServer(proxy string) ExecAllocatorOption
Query(sel interface{}, opts ...QueryOption) QueryAction
QueryAfter(sel interface{}, f func(context.Context, ...*cdp.Node) error, opts ...QueryOption) QueryAction
Reload() NavigateAction
RemoveAttribute(sel interface{}, name string, opts ...QueryOption) QueryAction
Reset(sel interface{}, opts ...QueryOption) QueryAction
Run(ctx context.Context, actions ...Action) error
Screenshot(sel interface{}, picbuf *[]byte, opts ...QueryOption) QueryAction	标签截图，赋值给变量
ScrollIntoView(sel interface{}, opts ...QueryOption) QueryAction
SendKeys(sel interface{}, v string, opts ...QueryOption) QueryAction	使用chromedp.ByID选择器。向标签输入内容。
SetAttributes(sel interface{}, attributes map[string]string, opts ...QueryOption) QueryAction
SetAttributeValue(sel interface{}, name, value string, opts ...QueryOption) QueryAction
SetJavascriptAttribute(sel interface{}, name, value string, opts ...QueryOption) QueryAction
SetUploadFiles(sel interface{}, files []string, opts ...QueryOption) QueryAction
SetValue(sel interface{}, value string, opts ...QueryOption) QueryAction
Sleep(d time.Duration) Action	等待时间
Stop() NavigateAction
Submit(sel interface{}, opts ...QueryOption) QueryAction
Targets(ctx context.Context) ([]*target.Info, error)
Text(sel interface{}, text *string, opts ...QueryOption) QueryAction
TextContent(sel interface{}, text *string, opts ...QueryOption) QueryAction
Title(title *string) Action
UserAgent(userAgent string) ExecAllocatorOption
UserDataDir(dir string) ExecAllocatorOption
Value(sel interface{}, value *string, opts ...QueryOption) QueryAction	取值并赋值给变量
WaitEnabled(sel interface{}, opts ...QueryOption) QueryAction
WaitFunc(wait func(context.Context, *cdp.Frame, ...cdp.NodeID) ([]*cdp.Node, error)) QueryOption
waitLoaded(ctx context.Context) error
WaitNewTarget(ctx context.Context, fn func(*target.Info) bool) <-chan target.ID
WaitNotPresent(sel interface{}, opts ...QueryOption) QueryAction
WaitNotVisible(sel interface{}, opts ...QueryOption) QueryAction
WaitReady(sel interface{}, opts ...QueryOption) QueryAction
WaitSelected(sel interface{}, opts ...QueryOption) QueryAction
WaitVisible(sel interface{}, opts ...QueryOption) QueryAction	等待指定标签元素加载完成
WindowSize(width, height int) ExecAllocatorOption	设置初始窗口大小的命令行选项。
WithBrowserOption(opts ...BrowserOption) ContextOption
WithDebugf(f func(string, ...interface{})) ContextOption
WithErrorf(f func(string, ...interface{})) ContextOption
WithLogf(f func(string, ...interface{})) ContextOption
WithTargetID(id target.ID) ContextOption

godet

• https://github.com/raff/godet (opens new window)

• 截图

package main

import "fmt"
import "time"

import "github.com/raff/godet"

func main() {
	// connect to Chrome instance
	remote, err := godet.Connect("localhost:9222", false)
	if err != nil {
		fmt.Println("cannot connect to Chrome instance:", err)
		return
	}

	// disconnect when done
	defer remote.Close()

	// get browser and protocol version
	version, _ := remote.Version()
	fmt.Println(version)

	// get list of open tabs
	tabs, _ := remote.TabList("")
	fmt.Println(tabs)

	// install some callbacks
	remote.CallbackEvent(godet.EventClosed, func(params godet.Params) {
		fmt.Println("RemoteDebugger connection terminated.")
	})

	remote.CallbackEvent("Network.requestWillBeSent", func(params godet.Params) {
		fmt.Println("requestWillBeSent",
			params["type"],
			params["documentURL"],
			params["request"].(map[string]interface{})["url"])
	})

	remote.CallbackEvent("Network.responseReceived", func(params godet.Params) {
		fmt.Println("responseReceived",
			params["type"],
			params["response"].(map[string]interface{})["url"])
	})

	remote.CallbackEvent("Log.entryAdded", func(params godet.Params) {
		entry := params["entry"].(map[string]interface{})
		fmt.Println("LOG", entry["type"], entry["level"], entry["text"])
	})

	// block loading of most images
	_ = remote.SetBlockedURLs("*.jpg", "*.png", "*.gif")

	// create new tab
	tab, _ := remote.NewTab("https://www.google.com")
	fmt.Println(tab)

	// enable event processing
	remote.RuntimeEvents(true)
	remote.NetworkEvents(true)
	remote.PageEvents(true)
	remote.DOMEvents(true)
	remote.LogEvents(true)

	// navigate in existing tab
	_ = remote.ActivateTab(tabs[0])

	//remote.StartPreciseCoverage(true, true)

	// re-enable events when changing active tab
	remote.AllEvents(true) // enable all events

	_, _ = remote.Navigate("https://www.google.com")

	// evaluate Javascript expression in existing context
	res, _ := remote.EvaluateWrap(`
            console.log("hello from godet!")
            return 42;
        `)
	fmt.Println(res)

	// take a screenshot
	_ = remote.SaveScreenshot("screenshot.png", 0644, 0, true)

	time.Sleep(time.Second)

	// or save page as PDF
	_ = remote.SavePDF("page.pdf", 0644, godet.PortraitMode(),
            godet.Scale(0.5), godet.Dimensions(6.0, 2.0))

	// if err := remote.SetInputFiles(0, []string{"hello.txt"}); err != nil {
	//     fmt.Println("setInputFiles", err)
	// }

	time.Sleep(5 * time.Second)

	//remote.StopPreciseCoverage()

	r, err := remote.GetPreciseCoverage(true)
	if err != nil {
		fmt.Println("error profiling", err)
	} else {
		fmt.Println(r)
	}

	// Allow downloads
	_ = remote.SetDownloadBehavior(godet.AllowDownload, "/tmp/")
	_, _ = remote.Navigate(url)

	time.Sleep(time.Second)

	// Block downloads
	_ = remote.SetDownloadBehavior(godet.DenyDownload, "")
	_, _ = remote.Navigate(url)
}

gcd

• https://github.com/wirepair/gcd (opens new window)

• 截图

package main

import (
	"encoding/base64"
	"flag"
	"fmt"
	"log"
	"net/url"
	"os"
	"runtime"
	"sync"
	"time"

	"github.com/wirepair/gcd"
	"github.com/wirepair/gcd/gcdapi"
)

const (
	numTabs = 5
)

var debugger *gcd.Gcd
var wg sync.WaitGroup

var path string
var dir string
var port string

func init() {
	switch runtime.GOOS {
	case "windows":
		flag.StringVar(&path, "chrome",
            "C:\\Program Files (x86)\\Google\\Chrome\\Application\\chrome.exe",
            "path to chrome")
		flag.StringVar(&dir, "dir", "C:\\temp\\", "user directory")
	case "darwin":
		flag.StringVar(&path, "chrome",
            "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome",
            "path to chrome")
		flag.StringVar(&dir, "dir", "/tmp/", "user directory")
	case "linux":
		flag.StringVar(&path, "chrome", "/usr/bin/chromium-browser", "path to chrome")
		flag.StringVar(&dir, "dir", "/tmp/", "user directory")
	}

	flag.StringVar(&port, "port", "9222", "Debugger port")
}

func main() {
	var err error
	urls := []string{"http://www.google.com", "http://www.veracode.com",
            "http://www.microsoft.com", "http://bbc.co.uk",
            "http://www.reddit.com/r/golang"}

	flag.Parse()

	debugger = gcd.NewChromeDebugger()
	debugger.StartProcess(path, dir, port)
	defer debugger.ExitProcess()

	targets := make([]*gcd.ChromeTarget, numTabs)

	for i := 0; i < numTabs; i++ {
		wg.Add(1)
		targets[i], err = debugger.NewTab()
		if err != nil {
			log.Fatalf("error getting targets")
		}
		page := targets[i].Page
		page.Enable()
		targets[i].Subscribe("Page.loadEventFired", pageLoaded)
		// navigate
		navigateParams := &gcdapi.PageNavigateParams{Url: urls[i]}
		_, _, _, err := page.NavigateWithParams(navigateParams)
		if err != nil {
			log.Fatalf("error: %s\n", err)
		}
	}
	wg.Wait()
	for i := 0; i < numTabs; i++ {
		takeScreenShot(targets[i])
	}
}

func pageLoaded(target *gcd.ChromeTarget, event []byte) {
	target.Unsubscribe("Page.loadEventFired")
	wg.Done()
}

func takeScreenShot(target *gcd.ChromeTarget) {
	dom := target.DOM
	page := target.Page
	doc, err := dom.GetDocument(-1, true)
	if err != nil {
		fmt.Printf("error getting doc: %s\n", err)
		return
	}

	debugger.ActivateTab(target)
	time.Sleep(1 * time.Second) // give it a sec to paint
	u, urlErr := url.Parse(doc.DocumentURL)
	if urlErr != nil {
		fmt.Printf("error parsing url: %s\n", urlErr)
		return
	}

	fmt.Printf("Taking screen shot of: %s\n", u.Host)
	screenShotParams := &gcdapi.PageCaptureScreenshotParams{Format: "png",
                                FromSurface: true}
	img, errCap := page.CaptureScreenshotWithParams(screenShotParams)
	if errCap != nil {
		fmt.Printf("error getting doc: %s\n", errCap)
		return
	}

	imgBytes, errDecode := base64.StdEncoding.DecodeString(img)
	if errDecode != nil {
		fmt.Printf("error decoding image: %s\n", errDecode)
		return
	}

	f, errFile := os.Create(u.Host + ".png")
	defer f.Close()
	if errFile != nil {
		fmt.Printf("error creating image file: %s\n", errFile)
		return
	}
	f.Write(imgBytes)
	debugger.CloseTab(target)
}