Java annotation to create constructor

Question

I am using PageFactory page object model for my Automation Framework. Now for every page class I have to create a constructor. For example:

public class StudentProfile {

    public StudentProfile (WebDriver driver) {
        this.driver = driver;
        PageFactory.initElements(driver, this);
    }
}

But I want to create a custom annotation. So that I don't have to repeat it again and again for each Page Class

@InitElements(driver)
public class StudentProfile {
    
        // to do 
    }

@InitElements(driver)
public class SchoolHomePage {
    
        // to do 
    }

I have gone through following tuts, but couldn't understand how am I going to implement it?

• https://www.baeldung.com/java-custom-annotation

• Can I make a constructor for a custom annotation?

Answer 1

You basically cannot. The annotation API offers only two primitives:

• Have the annotations be runtime-inspectable. This is great if you want to write a tool that, say, takes an instance of some class and uses annotations written on the fields of that class as guidance for serializing that instance into an XML or JSON blob. It does absolutely nothing for this use-case; you can't just add constructors to things at runtime and have that be useful (the constructors therefore do not exist at compile time which is obviously when you want them).

• Have an annotation processor plug into the compilation process and it can see them. But, out of the box and by the API, annotation processors can generate new files; it cannot modify existing ones. Thus, it cannot add that constructor either.

There is a third option: Project Lombok which uses annotations and can generate code in existing files on-the-fly. But it's rocket science - we (I'm one of the core contributors) write custom code for various compilers and do some barely (to straight up un-)supported shenanigans along with a lot of maintenance effort to make sure everything keeps working.

This sounds like a fine task for a custom, just-for-your-project-and-no-others lombok addition which we don't meaningfully support. You can of course fork lombok off of github and add this if you must, but we have no tutorials for how to do that, and we don't recommend it.

Other than lombok (which is tricky), this is a straight up -impossible-, unfortunately.