selenium—- webdriver原理

之前看乙醇视频中提到，selenium 的ruby 实现有一个小后门，在代码中加上$DEBUG=1 ，再运行脚本的过程中，就可以看到客户端请求的信息与服务器端返回的数据；觉得这个功能很强大，可以帮助理解webdriver的运行原理。

后来查了半天，python并没有提供这样一个方便的后门，不过我们可以通过代理的方式获得这些交互信息；

一、需要安装java 虚拟机与selenium-server-standalone ，参考 《selenium + python自动化测试环境搭建》第7、8操作：

二、通过下面命令启动服务：

C:\selenium>java -jar selenium-server-standalone-2.33.0.jar

在命令结尾加 >d:\log.txt 可以将命令信息存入文件，但信息很少。

然后运行下面的自动化脚本：

  1. #coding = utf-8import timefrom selenium import webdriverfrom selenium.webdriver.common.desired_capabilities import DesiredCapabilitiesdriver = webdriver.Remote(desired_capabilities=DesiredCapabilities.CHROME)driver.get("http://www.youdao.com")driver.find_element_by_name("q").send_keys("hello")driver.find_element_by_name("q").send_keys("key.ENTER")driver.close()

webdriver原理：

  • WebDriver 启动目标浏览器，并绑定到指定端口。该启动的浏览器实例，做为web driver的remote server。

  • Client 端通过CommandExcuter 发送HTTPRequest 给remote server 的侦听端口（通信协议： the webriver wire protocol）

  • Remote server 需要依赖原生的浏览器组件（如：IEDriver.dll,chromedriver.exe），来转化转化浏览器的native调用。

查看命令提示符下的运行日志：

咋一看很乱，慢慢分析一下就发现很有意思！结合上面的脚本分析

  • 启动代理进入监听状态
  1. C:\selenium>java -jar selenium-server-standalone-2.33.0.jar八月 22, 2013 10:19:48 上午 org.openqa.grid.selenium.GridLauncher mainINFO: Launching a standalone server10:19:48.734 INFO - Java: Oracle Corporation 23.21-b0110:19:48.734 INFO - OS: Windows XP 5.1 x8610:19:48.734 INFO - v2.33.0, with Core v2.33.0. Built from revision 4e90c9710:19:48.843 INFO - RemoteWebDriver instances should connect to: http://127.0.0.1:4444/wd/hub10:19:48.843 INFO - Version Jetty/5.1.x10:19:48.843 INFO - Started HttpContext[/selenium-server/driver,/selenium-server/driver]10:19:48.843 INFO - Started HttpContext[/selenium-server,/selenium-server]10:19:48.843 INFO - Started HttpContext[/,/]10:19:48.890 INFO - Started org.openqa.jetty.jetty.servlet.ServletHandler@176343e10:19:48.890 INFO - Started HttpContext[/wd,/wd]10:19:48.906 INFO - Started SocketListener on 0.0.0.0:444410:19:48.906 INFO - Started org.openqa.jetty.jetty.Server@388c74
  • 创建新session 
  1. 10:20:38.593 INFO - Executing: [new session: {platform=ANY, javascriptEnabled=true, browserName=chrome, version=}] at URL: /session)10:20:38.593 INFO - Creating a new session for Capabilities [{platform=ANY, javascriptEnabled=true, browserName=chrome, version=}]
  • webdrivr通过GET方式发送请求
  1. [0.921][INFO]: received Webriver request: GET /status
  • 向webdrver返回响应，返回码200表示成功
  1. [0.921][INFO]: sending Webriver response: 200 {   "sessionId": "",   "status": 0,   "value": {      "build": {         "version": "alpha"      },      "os": {         "arch": "x86",         "name": "Windows NT",         "version": "5.1 SP3"      }   }}
  • webdriver 再次以POST方式发送请求，并启动浏览器相关信息
  1. [0.984][INFO]: received Webriver request: POST /session {   "desiredCapabilities": {      "browserName": "chrome",      "javascriptEnabled": true,      "platform": "ANY",      "version": ""   }}[0.984][INFO]: Launching chrome: "C:\ocuments and Settings\Administrator\Local Settings\Application ata\Google\Chrome\Application\chrome.exe" —remote-debugging-port=4223 —no-first-run —enable-logging —logging-level=1 —user-data-dir="C:\OCUME~1\AMINI~1\LOCALS~1\Temp\scoped_dir1808_7550" —load-extension="C:\OCUME~1\AMINI~1\LOCALS~1\Temp\scoped_dir1808_26821\internal" —ignore-certificate-errors data:text/html;charset=utf-8,[1.773][INFO]: sending Webriver response: 303
  • webdriver再次以GET方法请求，这附加上了session的信息
  1. [1.778][INFO]: received Webriver request: GET /session/32b33aa585ccbbf7ba78535882852af3
  • 服务器先对sesssionID进行解析，确认是selenium调用的以及要访问的网址，
  1. [1.779][INFO]: sending Webriver response: 200 {   "sessionId": "32b33aa585ccbbf7ba78535882852af3",   "status": 0,   "value": {      "acceptSslCerts": true,      "applicationCacheEnabled": false,      "browserConnectionEnabled": false,      "browserName": "chrome",      "chrome": {         "chromedriverVersion": "2.0"      },      "cssSelectorsEnabled": true,      "databaseEnabled": true,      "handlesAlerts": true,      "javascriptEnabled": true,      "locationContextEnabled": true,      "nativeEvents": true,      "platform": "Windows NT",      "rotatable": false,      "takesScreenshot": true,      "version": "27.0.1453.116",      "webStorageEnabled": true   }}10:20:40.640 INFO - Done: /session10:20:40.640 INFO - Executing: org.openqa.selenium.remote.server.handler.GetSessionCapabilities@14cf7a1 at URL: /session/ac5b2c71-5b1a-469e-814c-fdd09a2061fc)10:20:40.640 INFO - Done: /session/ac5b2c71-5b1a-469e-814c-fdd09a2061fc
  1. 10:20:40.656 INFO - Executing: [get: http://www.youdao.com] at URL: /session/ac5b2c71-5b1a-469e-814c-fdd09a2061fc/url)
  • webdriver正试向服务器请求youdao网站
  1. [1.820][INFO]: received Webriver request: POST /session/32b33aa585ccbbf7ba78535882852af3/url {   "url": "http://www.youdao.com"}[1.822][INFO]: waiting for pending navigations…[1.829][INFO]: done waiting for pending navigations[2.073][INFO]: waiting for pending navigations…[2.900][INFO]: done waiting for pending navigations
  • 获得服务器数据的应答
  1. [2.900][INFO]: sending Webriver response: 200 {   "sessionId": "32b33aa585ccbbf7ba78535882852af3",   "status": 0,   "value": null}10:20:41.734 INFO - Done: /session/ac5b2c71-5b1a-469e-814c-fdd09a2061fc/url
  • 下面，接着发送定位输入框的信息
  1. 10:20:41.734 INFO - Executing: [find element: By.name: q] at URL: /session/ac5b2c71-5b1a-469e-814c-fdd09a2061fc/element)[2.905][INFO]: received Webriver request: POST /session/32b33aa585ccbbf7ba78535882852af3/element {   "using": "name",   "value": "q"}[2.905][INFO]: waiting for pending navigations…[2.905][INFO]: done waiting for pending navigations[2.922][INFO]: waiting for pending navigations…[2.922][INFO]: done waiting for pending navigations
  • 得到服务器应答
  1. [2.922][INFO]: sending Webriver response: 200 {   "sessionId": "32b33aa585ccbbf7ba78535882852af3",   "status": 0,   "value": {      "ELEMENT": "0.19427558477036655:1"   }}10:20:41.765 INFO - Done: /session/ac5b2c71-5b1a-469e-814c-fdd09a2061fc/element
  1. 10:20:41.765 INFO - Executing: [send keys: 0 org.openqa.selenium.support.events.EventFiringWebDriver$EventFiringWebElement@a8215ba9, [h, e, l, l, o]] at URL: /session/ac5b2c71-5b1a-469e-814c-fdd09a2061fc/element/0/value)

向定位到的输入框写入hello

  1. [2.936][INFO]: received Webriver request: POST /session/32b33aa585ccbbf7ba78535882852af3/element/0.19427558477036655:1/value {   "id": "0.19427558477036655:1",   "value": [ "h", "e", "l", "l", "o" ]}[2.936][INFO]: waiting for pending navigations…[2.936][INFO]: done waiting for pending navigations[3.002][INFO]: waiting for pending navigations…[3.002][INFO]: done waiting for pending navigations[3.002][INFO]: sending Webriver response: 200 {   "sessionId": "32b33aa585ccbbf7ba78535882852af3",   "status": 0,   "value": null}10:20:41.843 INFO - Done: /session/ac5b2c71-5b1a-469e-814c-fdd09a2061fc/element/0/value
  • 再次发送定位输入框的请求
  1. 10:20:41.843 INFO - Executing: [find element: By.name: q] at URL: /session/ac5b2c71-5b1a-469e-814c-fdd09a2061fc/element)[3.006][INFO]: received Webriver request: POST /session/32b33aa585ccbbf7ba78535882852af3/element {   "using": "name",   "value": "q"}[3.006][INFO]: waiting for pending navigations…[3.006][INFO]: done waiting for pending navigations[3.016][INFO]: waiting for pending navigations…[3.016][INFO]: done waiting for pending navigations[3.016][INFO]: sending Webriver response: 200 {   "sessionId": "32b33aa585ccbbf7ba78535882852af3",   "status": 0,   "value": {      "ELEMENT": "0.19427558477036655:1"   }}10:20:41.859 INFO - Done: /session/ac5b2c71-5b1a-469e-814c-fdd09a2061fc/element
  1. 10:20:41.859 INFO - Executing: [send keys: 0 org.openqa.selenium.support.events.EventFiringWebDriver$EventFiringWebElement@a8215ba9, [k, e, y, ., E, N, T, E, R]] at URL: /session/ac5b2c71-5b1a-469e-814c-fdd09a2061fc/element/0/value)
  • 对定位的到的输入框发送回车（ENTER）事件请求
  1. [3.021][INFO]: received Webriver request: POST /session/32b33aa585ccbbf7ba78535882852af3/element/0.19427558477036655:1/value {   "id": "0.19427558477036655:1",   "value": [ "k", "e", "y", ".", "E", "N", "T", "E", "R" ]}[3.021][INFO]: waiting for pending navigations…[3.021][INFO]: done waiting for pending navigations[3.064][INFO]: waiting for pending navigations…[3.064][INFO]: done waiting for pending navigations[3.064][INFO]: sending Webriver response: 200 {   "sessionId": "32b33aa585ccbbf7ba78535882852af3",   "status": 0,   "value": null}10:20:41.906 INFO - Done: /session/ac5b2c71-5b1a-469e-814c-fdd09a2061fc/element/0/value
  1. 10:20:41.906 INFO - Executing: [close window] at URL: /session/ac5b2c71-5b1a-469e-814c-fdd09a2061fc/window)[3.068][INFO]: received Webriver request: ELETE /session/32b33aa585ccbbf7ba78535882852af3/window[WARNING:chrome_desktop_impl.cc(88)] chrome detaches, user should take care of directory:C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\scoped_dir1808_7550 and C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\scoped_dir1808_26821[5.318][INFO]: sending Webriver response: 200 {   "sessionId": "32b33aa585ccbbf7ba78535882852af3",   "status": 0,   "value": null}10:20:44.156 INFO - Done: /session/ac5b2c71-5b1a-469e-814c-fdd09a2061fc/window

request请求 / response应答

一次请求会对应一次应答

POST/GET是请求(request)两种类型；关于两种请求方式的类别参考其它资料

200 、203是 HTTP请求返回的状态码，200表示成功；

sessionid ：每一个访问服务器的客户端，都要先得到服务器端分配的一个sessionid ，就像通行证一样，只有得到sessionid的客户端才能向服务器请求想要的数据。

其它还包括操作系统版本，浏览器类型、URL、字符类型等非常详细的记录。熟悉HTTP ，了解TCP 的三次握手四次挥手，相信你对浏览器的交互与webdriver原理会有更深入的认识。

http://www.cnblogs.com/fnng/p/3274186.html

http://download.csdn.net/download/fnngj/6041329