Selenium: annotation type not applicable to this kind of declaration
The reason for that being that the annotation is not applicable to local variables.
Further, the actual definition of the annotation in the documentation is :
@Retention(value=RUNTIME)@Target(value={FIELD,TYPE})public @interface FindBySo, seemingly the annotation would still be applicable to fields. You can fix the same, by moving the variable to the global level (class attribute) as:
class WelcomePage { @FindBy(partialLinkText = "Books") private WebElement books; .... // everything else void populateCatalogue() { // use 'books' here }}