phantomjsdriver

To use PhantomJS, as with other browsers, you must install it for your platform. Mac OSX Yosmite users should download an unofficial, patched version from here.

As of this writing, if you are able to use the currently most up-to-date version of PhantomJS, you should add the following to your project's dependencies:

:dependencies [[com.codeborne/phantomjsdriver "1.2.1"
                                              :exclusions [org.seleniumhq.selenium/selenium-java
                                                          org.seleniumhq.selenium/selenium-server
                                                          org.seleniumhq.selenium/selenium-remote-driver]]
               [org.seleniumhq.selenium/selenium-java "x.y.z"]]

If you don't add the :exclusions you are likely to see aberrant behavior.

PhantomJS supports JavaScript execution and even screenshots. Read up on PhantomJS' documentation as well as the implementation of the driver. (There is an announcement about the official source repo.