Is it possible to do server side validations for arrays,Arraylist,Objects using the default annotations provided by Struts2?
Of course, you need to use the Visitor Field Validator.
Long time ago I've written something about using it (in XML) here;
Basically, you write validation rules for ONE object (or "Row"), and you tell the Action to validate that object with Visitor Validator; if you send an array or a list of 100 objects (from the JSP to the Action), each of them will be validated through the visitor validator that is placed (or annotated) in the package where the object is declared, not in the Action package.