Struts Beginner question - validation (enter string into field for double)

how to capture input type problem in validation?
in my ActionForm, i have this property 'cost' which i declared as double, and its getter and setter method as below:

public void setCost(double d){cost = d;}
public double getCost(){return cost;}

so how do i capture this type mismatch error in my validation? I want it to be able to go back to the input jsp and display an error msg.

please let me know if my question is not clear.Start Free Trial