之前写过Selenium是怎么指挥浏览器运行的，其中提到过通过CDP(Chrome DevTools Protocol)协议可以直接绕过浏览器驱动来控制浏览器。CDP本质上就是通过WebSocket协议传输JSON格式的命令。
使用CDP时，无需浏览器驱动，但依然依赖浏览器。因此，控制浏览器的第一步就是启动浏览器。这里我们使用ps ajx命令结果是否包含Chrome、headless两个关键词来判断是否已启动CDP服务，也就是代码中的chromeHeadlessRunning函数：
func chromeHeadlessRunning() (bool, error) {
cmd := exec.Command("ps", "ajx")
output, err := cmd.Output()
if err != nil {
return false, err
}
scanner := bufio.NewScanner(strings.NewReader(string(output)))
for scanner.Scan() {
line := scanner.Text()
if strings.Contains(line, "Chrome") &&
strings.Contains(line, "headless") &&
!strings.Contains(line, "grep") {
return true, nil
}
}
return false, nil
}
怎么判断启动CDP服务的命令确实拉起了CDP？CDP协议使用常用的TCP/IP协议栈，只需要发起连接多次几次，成功建立连接视为服务成功启动。
func waitForCDP(port string, timeout time.Duration) bool {
deadline := time.Now().Add(timeout)
for time.Now().Before(deadline) {
conn, err := net.DialTimeout("tcp", port, time.Second)
if err == nil {
conn.Close()
return true
}
time.Sleep(200 * time.Millisecond)
}
return false
}
到这一步，基本的要求都已满足。那么通过HTTP的PUT方法新建一个页面，并获取对应的webSocketDebuggerUrl用于后续交互。
func getDebuggerInfo() interface{} {
httpClient := http.Client{}
req, err := http.NewRequest(http.MethodPut, debuggerBaseUrl+"/json/new", nil)
isFatal(err)
res, err := httpClient.Do(req)
isFatal(err)
defer res.Body.Close()
bodyBytes, err := io.ReadAll(res.Body)
isFatal(err)
var i interface{}
err = json.Unmarshal(bodyBytes, &i)
isFatal(err)
return i
}
现在就可以通过webSocketDebuggerUrl建立WebSocket连接控制浏览器了。以获取https://baidu.com网页标题为例：
func testWeb() {
testUrl := "https://baidu.com"
var readTimeout time.Duration = 3
debugInfo := getDebuggerInfo()
if v, ok := debugInfo.(map[string]interface{}); ok {
if wsUrl, ok := v["webSocketDebuggerUrl"].(string); ok {
wsClient, err := websocket.Dial(wsUrl, "", debuggerBaseUrl)
defer wsClient.Close()
isFatal(err)
_, err = wsClient.Write([]byte(`{"id":1,"method":"Page.navigate","params":{"url":"` + testUrl + `"}}`))
isFatal(err)
b := make([]byte, 1)
log.Println(wsClient.SetReadDeadline(time.Now().Add(time.Second * readTimeout)))
for n, err := wsClient.Read(b); err == nil && n > 0; n, err = wsClient.Read(b) {
fmt.Printf("%s", b[:n])
}
fmt.Println()
_, err = wsClient.Write([]byte(`{"id":2,"method":"Runtime.evaluate","params":{"expression":"document.title","returnByValue":true}}`))
isFatal(err)
log.Println(wsClient.SetReadDeadline(time.Now().Add(time.Second * readTimeout)))
resJson := make([]byte, 0) // 用于处理百度的中文标题
for n, err := wsClient.Read(b); err == nil && n > 0; n, err = wsClient.Read(b) {
fmt.Printf("%s", b[:n])
resJson = append(resJson, b[:n]...)
}
fmt.Println()
x := struct {
Id int `json:"id"`
Result struct {
Result struct {
Type string `json:"type"`
Value string `json:"value"`
}
}
}{}
err = json.Unmarshal(resJson, &x)
if err != nil {
log.Println(err)
}
fmt.Println(x.Result.Result.Value)
} else {
log.Printf("WebSocketDebuggerUrl 不是字符串: %#v\n", wsUrl)
}
} else {
log.Println("响应体不是 JSON 格式")
}
}
完整的代码如下：
package main
import (
"bufio"
"encoding/json"
"fmt"
"golang.org/x/net/websocket"
"io"
"log"
"net"
"net/http"
"os/exec"
"strings"
"time"
)
var debuggingPort = "9222"
var debuggerBaseUrl = "http://127.0.0.1:" + debuggingPort
var command = "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome"
var options = []string{"--remote-debugging-port=" + debuggingPort, "--headless", "--disable-gpu", "--no-sandbox", "--user-data-dir=/tmp/chromeCDP", "--remote-allow-origins=*"}
func isFatal(err error) {
if err != nil {
log.Fatalln(err)
}
}
func chromeHeadlessRunning() (bool, error) {
cmd := exec.Command("ps", "ajx")
output, err := cmd.Output()
if err != nil {
return false, err
}
scanner := bufio.NewScanner(strings.NewReader(string(output)))
for scanner.Scan() {
line := scanner.Text()
if strings.Contains(line, "Chrome") &&
strings.Contains(line, "headless") &&
!strings.Contains(line, "grep") {
return true, nil
}
}
return false, nil
}
func waitForCDP(port string, timeout time.Duration) bool {
deadline := time.Now().Add(timeout)
for time.Now().Before(deadline) {
conn, err := net.DialTimeout("tcp", port, time.Second)
if err == nil {
conn.Close()
return true
}
time.Sleep(200 * time.Millisecond)
}
return false
}
func getDebuggerInfo() interface{} {
httpClient := http.Client{}
req, err := http.NewRequest(http.MethodPut, debuggerBaseUrl+"/json/new", nil)
isFatal(err)
res, err := httpClient.Do(req)
isFatal(err)
defer res.Body.Close()
bodyBytes, err := io.ReadAll(res.Body)
isFatal(err)
var i interface{}
err = json.Unmarshal(bodyBytes, &i)
isFatal(err)
return i
}
func testWeb() {
testUrl := "https://baidu.com"
var readTimeout time.Duration = 3
debugInfo := getDebuggerInfo()
if v, ok := debugInfo.(map[string]interface{}); ok {
if wsUrl, ok := v["webSocketDebuggerUrl"].(string); ok {
wsClient, err := websocket.Dial(wsUrl, "", debuggerBaseUrl)
defer wsClient.Close()
isFatal(err)
_, err = wsClient.Write([]byte(`{"id":1,"method":"Page.navigate","params":{"url":"` + testUrl + `"}}`))
isFatal(err)
b := make([]byte, 1)
log.Println(wsClient.SetReadDeadline(time.Now().Add(time.Second * readTimeout)))
for n, err := wsClient.Read(b); err == nil && n > 0; n, err = wsClient.Read(b) {
fmt.Printf("%s", b[:n])
}
fmt.Println()
_, err = wsClient.Write([]byte(`{"id":2,"method":"Runtime.evaluate","params":{"expression":"document.title","returnByValue":true}}`))
isFatal(err)
log.Println(wsClient.SetReadDeadline(time.Now().Add(time.Second * readTimeout)))
resJson := make([]byte, 0) // 用于处理百度的中文标题
for n, err := wsClient.Read(b); err == nil && n > 0; n, err = wsClient.Read(b) {
fmt.Printf("%s", b[:n])
resJson = append(resJson, b[:n]...)
}
fmt.Println()
x := struct {
Id int `json:"id"`
Result struct {
Result struct {
Type string `json:"type"`
Value string `json:"value"`
}
}
}{}
err = json.Unmarshal(resJson, &x)
if err != nil {
log.Println(err)
}
fmt.Println(x.Result.Result.Value)
} else {
log.Printf("WebSocketDebuggerUrl 不是字符串: %#v\n", wsUrl)
}
} else {
log.Println("响应体不是 JSON 格式")
}
}
func main() {
running, err := chromeHeadlessRunning()
isFatal(err)
if !running {
fmt.Println("未检测到 Chrome headless，启动中...")
go func() {
err := exec.Command(command, options...).Run()
isFatal(err)
}()
fmt.Println("等待 Chrome headless 启动...")
if !waitForCDP("127.0.0.1:"+debuggingPort, 10*time.Second) {
fmt.Println("Chrome headless 启动超时")
return
}
fmt.Println("Chrome headless 启动成功")
} else {
fmt.Println("Chrome headless 已在运行")
}
fmt.Println("执行后续逻辑...")
testWeb()
}
运行效果。
