how does selenium webdriver upload files to the browser?

Question

I am a javascript/java developer and I have been trying to figure out how the selenium webdriver automation framework uploads files from the file system. It is impossible to set a file input via javascript because it is a security violation. Yet somehow webdriver is able to do this with the following command:

driver.setFileDetector(new LocalFileDetector());
WebElement upload = driver.findElement(By.id("myfile"));
upload.sendKeys("/Users/sso/the/local/path/to/darkbulb.jpg");
driver.findElement(By.id("submit")).click();

So they are setting the value by sending keys to it? I don't get it. I have looked through the source code found here: http://code.google.com/p/selenium/source/checkout I am still not able to find where they do this.

Edit: My question is not how to do this with selenium, but how did the selenium developers make this possible? How did they get around the security restrictions in javascript? How are they uploading the file?

Answer 1

Nice question buddy...they have written a HTTP proxy to solve the Javascript secuirty restrictions. Using this proxy made it possible to side-step many of the constraints of the "same host origin" policy, where a browser won't allow Javascript to make calls to anything other than the server from which the current page has been served.

Moreover WebDriver uses the alternative approach of firing events at the OS level. As these "native events" aren't generated by the browser this approach circumvents the security restrictions placed on synthesized events and, because they are OS specific, once they are working for one browser on a particular platform reusing the code in another browser is relatively easy.

Most of the content above is referenced from the below..do read the following reference for more details on Selenium internals

http://www.aosabook.org/en/selenium.html