Events
What is Event ?
Event is any action performed on webpage elements using selenium webdriver, actions like finding an element, clicking an element, navigating to url, raising an exception, changing value in a field, navigating back, navigating forth, executing an javascript.
Even are present across all programming languages, in some languages they call it as event sink.
Event Listeners
What is Event Listener?
An event listeners are set of functions in a selenium that waits for an event to occur; that event may be a user clicking or finding, changing value, or an Exception. The listeners are programmed to react to an input or signal.
There is a function to react when an even about to happen, also there is a function to react after event.
In Simple way : If person A tries to slap perform B, person B tries to escape the hit (before event), unfortunately if A slaps person B. Then B reacts to it either by slapping or by keeping mouth shut (after event).
Even though selenium webdriver provides listeners , it doesn't provide details what to do when an event occurs. User must provide all the details what should happened when an event occurs.
For Example: User should implement method for what should happen before and after a click.
Benefits of Event Listeners
- It allows do something before or after an action. For example, if you want to wait for an ajax element before every click, or log that action into logger, it is possible to do with the event listener.
- Take screenshots when exception occurred.
- Log the action of the selenium
- To take screenshots on on every action like when you navigate go a page, when an value changes so on
- To capture values before changing the values
- Track the urls
- To check state of the element
EventFiringWebDriver
EventFiringWebDriver is a wrapper on the webdriver, it provides all the methods which webdriver provides.
EventFiringWebDriver provide two more methods to
Event Listeners present in Selenium
Webdriver provides pre and post even listeners.
beforeAlertAccept(WebDriver arg0) :
This methods will be invoked before accepting an alert, this methods accepts driver as parameter
afterAlertAccept(WebDriver arg0)
this method will be invoked once user accepts the alert with script, this methods accepts driver as parameter
beforeAlertDismiss(WebDriver arg0)
beforeAlertDismiss method will be invoked before an alert is dismissed, this methods accepts driver as parameter
afterAlertDismiss(WebDriver arg0)
afterAlertDismiss method will be invoked after dismissing an alert, this methods accepts driver as parameter
beforeChangeValueOf(WebElement arg0, WebDriver arg1, CharSequence[] arg2) :
beforeChangeValueOf method will be invoked when we try to change the value of the element, this methods accepts the target element, driver, and the text
afterChangeValueOf(WebElement arg0, WebDriver arg1, CharSequence[] arg2) :
afterChangeValueOf method will be invoked when the target element's values changes, this method accepts target element, driver, and text.
beforeClickOn(WebElement arg0, WebDriver arg1) :
beforeClickOn method will be invoked before clicking and element with click() method in selenium, this method accepts webelement and webdriver as parameters
afterClickOn(WebElement arg0, WebDriver arg1) :
This method will be invoked after the click() method's operation.
beforeFindBy(By arg0, WebElement arg1, WebDriver arg2) :
beforeFindBy method will be invoked before finding the element with findElement method, this method accepts By class parameter and two webelements
afterFindBy(By arg0, WebElement arg1, WebDriver arg2) :
afterFindBy method will be invoked after the operation of findElement
beforeNavigateBack(WebDriver arg0) :
beforeNavigateBack this method will be invoked before executing back() method from Navigation class, this method accepts driver as parameter
afterNavigateBack(WebDriver arg0) :
afterNavigateBack method will be executed after executing back() method
beforeNavigateForward(WebDriver arg0)
beforeNavigateForward will be invoked before executing forward() method from Navigation class, this method accepts driver as parameter
afterNavigateForward(WebDriver arg0) :
afterNavigateForward method will be invoked after executing forward() method from Navigation class.
beforeNavigateRefresh(WebDriver arg0) :
beforeNavigateRefresh method will be executed before executing refresh() method from Navigation class, this method accepts driver as parameter
afterNavigateRefresh(WebDriver arg0) :
afterNavigateRefresh method will be executed after refreshing the page with refresh() method from Navigation class
beforeNavigateTo(String arg0, WebDriver arg1)
beforeNavigateTo method will be executed before navigating to nay webpage using to() method from Navigation class, this method accepts String webaddress and driver as parameters
afterNavigateTo(String arg0, WebDriver arg1) :
afterNavigateTo method will be executed after executing to() method
beforeScript(String arg0, WebDriver arg1)
beforeScript method will be executed before executing any javascript code with JavaScriptExecutor
afterScript(String arg0, WebDriver arg1):
afterScript method will be executed after executing javascript code.
onException(Throwable arg0, WebDriver arg1)
onException method will be executed whenever there is an exception occurs in selenium, irrespective of whether user handles the exception or not, this method will be executed
Implement Webdriver Listeners
Steps to implement listeners in webbdriver :
2. Register the event handling class
Steps in detail :
1. Create a java Class called ListenerHelper
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.support.events.WebDriverEventListener;
public class ListenerHelper implements WebDriverEventListener{
@Override
public void afterAlertAccept(WebDriver arg0) {
System.out.println("Alert Accepted");
}
@Override
public void afterAlertDismiss(WebDriver arg0) {
System.out.println("Alert Dismissed");
}
@Override
public void afterChangeValueOf(WebElement arg0, WebDriver arg1, CharSequence[] arg2) {
System.out.println("The value in the element after changing : "+arg2[0]);
}
@Override
public void afterClickOn(WebElement arg0, WebDriver arg1) {
System.out.println("Element clicked");
}
@Override
public void afterFindBy(By arg0, WebElement arg1, WebDriver arg2) {
System.out.println("Element found");
}
@Override
public void afterNavigateBack(WebDriver arg0) {
System.out.println("Navigating back to : "+arg0.getCurrentUrl());
}
@Override
public void afterNavigateForward(WebDriver arg0) {
System.out.println("Navigating forward to : "+arg0.getCurrentUrl());
}
@Override
public void afterNavigateRefresh(WebDriver arg0) {
System.out.println("Url after refreshing : "+arg0.getCurrentUrl());
}
@Override
public void afterNavigateTo(String arg0, WebDriver arg1) {
System.out.println("navigating to url : "+arg0);
}
@Override
public void afterScript(String arg0, WebDriver arg1) {
System.out.println("Executed javascript : "+arg0);
}
@Override
public void beforeAlertAccept(WebDriver arg0) {
System.out.println("Before accepting alert");
}
@Override
public void beforeAlertDismiss(WebDriver arg0) {
System.out.println("Before dismissing alert");
}
@Override
public void beforeChangeValueOf(WebElement arg0, WebDriver arg1, CharSequence[] arg2) {
System.out.println("Before changing the value : "+arg2[0]);
}
@Override
public void beforeClickOn(WebElement arg0, WebDriver arg1) {
System.out.println("Trying to click on the element");
}
@Override
public void beforeFindBy(By arg0, WebElement arg1, WebDriver arg2) {
System.out.println("Trying to find the element");
}
@Override
public void beforeNavigateBack(WebDriver arg0) {
System.out.println("Url before navigating back : "+arg0.getCurrentUrl());
}
@Override
public void beforeNavigateForward(WebDriver arg0) {
System.out.println("Url before navigating forard");
}
@Override
public void beforeNavigateRefresh(WebDriver arg0) {
System.out.println("Url before refreshing page : "+arg0.getCurrentUrl());
}
@Override
public void beforeNavigateTo(String arg0, WebDriver arg1) {
System.out.println("Current Ur : "+arg1.getCurrentUrl());
}
@Override
public void beforeScript(String arg0, WebDriver arg1) {
System.out.println("Executing javascript : " +arg0);
}
@Override
public void onException(Throwable arg0, WebDriver arg1) {
System.out.println("Exception throwed : "+arg0.getMessage());
}
}
2. Create class called ActualDriver
3. Create object for Browser
System.setProperty("webdriver.gecko.driver", "C:/~/geckodriver.exe");
WebDriver driver = new FirefoxDriver();
4. Create object for ListenerHelper inside ActualDriver class
ListenerHelper listen = new ListenerHelper();
5. Create Object for EventFiringWebDriver
, it accepts the driver as parameter
EventFiringWebDriver browser = new EventFiringWebDriver(driver);
6. Register the Listener onto EventFiringWebDriver object
browser.register(listen);
7. Write the scripts using EventFiringWebDriver object
browser.get("https://google.com");
Complete ActualDriver code:
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.openqa.selenium.support.events.EventFiringWebDriver;
public class ActualDriver {
public static void main(String[] args) {
System.setProperty("webdriver.gecko.driver", "C:/~/geckodriver.exe");
WebDriver driver = new FirefoxDriver();
ListenerHelper listen = new ListenerHelper();
EventFiringWebDriver browser = new EventFiringWebDriver(driver);
browser.register(listen);
browser.get("https://google.com");
browser.findElement(By.name("q")).sendKeys("Sendkeys with listener");
browser.findElement(By.xpath("//input[contains(@value,'Search')]")).click();
}
}
Output :
Recommended Readings
- Log4J with Properties file
- Annotations in TestNG
- Handling Cookies with Selenium Webdriver
- Write Excel with Apache POI
- Read Multiple Property Files
- Handle Alerts in Selenium Webdriver
- Take Screenshot with Robot Class
- kill Process ByName in CMD with selenium
- HtmlUnitDriver in Selenium
- Selenium Interview Questions
About Author
Article is written by Pavan (a) KarthiQ. Well, I am serving notice period in an MNC, Bangalore. I thought to enrich every person knowledge a little, I always have a feeling, when we teach something, we will learn more than what you know.
Knowledge is the only thing that doubles when you spend it.
I have also created the reporter for Protractor Jasmine. Use for your projects without any hesitation