My question is: do webelements decorated with findby attributes call the findelement function upon each reference to them? If not, when?
And what is the procedure with List< webelement > which is also decorated? Does it trigger when you reference the list, or when you reference an element inside that list?
I'm asking because I have some situations where I'm getting stale element exceptions and I want to know how to deal with them.
WebElements are evaluated lazily. That is, if you never use a WebElement field in a PageObject, there will never be a call to "findElement" for it. Reference.
If don't want WebDriver to query the element each time, you have to use the @CacheLookup annotation.
What about the list part of my question?
The findElements is triggered when you query from the list. Say you have:
@FindBy(xpath = "//div[@class=\"langlist langlist-large\"]//a")
private List<WebElement> list;
Following code samples all trigger the findElements :
list.isEmpty();
WebElement element = list.get(0);
Where as
List<WebElement> newList = new ArrayList<WebElement>();
newList = list;
does not trigger the findElements().
Please check the LocatingElementListHandler class. I suggest diving into the source for answers.
You may find this code comment from PageFactory class helpful:
/**
* Instantiate an instance of the given class, and set a lazy proxy for each of the WebElement
* and List<WebElement> fields that have been declared, assuming that the field name is also
* the HTML element's "id" or "name". This means that for the class:
*
* <code>
* public class Page {
* private WebElement submit;
* }
* </code>
*
* there will be an element that can be located using the xpath expression "//*[@id='submit']" or
* "//*[@name='submit']"
*
* By default, the element or the list is looked up each and every time a method is called upon it.
* To change this behaviour, simply annotate the field with the {@link CacheLookup}.
* To change how the element is located, use the {@link FindBy} annotation.
*
* This method will attempt to instantiate the class given to it, preferably using a constructor
* which takes a WebDriver instance as its only argument or falling back on a no-arg constructor.
* An exception will be thrown if the class cannot be instantiated.
*
* @see FindBy
* @see CacheLookup
* @param driver The driver that will be used to look up the elements
* @param pageClassToProxy A class which will be initialised.
* @return An instantiated instance of the class with WebElement and List<WebElement> fields proxied
*/