API / Apache Wicket Interview questions
What is the difference between IValidator and form-level validation in Wicket?
Both check user input before it's accepted, but they operate at different scopes: one field at a time versus the whole submitted form as a unit.
| IValidator | Form-level validation (Form.onValidate()) |
| Attached to a single FormComponent | Overridden on the Form itself |
| Checks one field's converted value in isolation | Checks relationships between multiple fields |
| Example: email format, string length, numeric range | Example: "password" and "confirm password" must match |
| Runs during each field's own validation phase | Runs after individual field validators have passed |
Both report problems the same way — through Wicket's feedback message system, typically rendered via a FeedbackPanel — so from the user's point of view the distinction is invisible; it only matters to the developer deciding where a particular rule naturally belongs: on the one field it concerns, or on the form as a whole when the rule spans more than one field.
Which validation approach is the right fit for enforcing that "password" and "confirm password" match?
Through what shared mechanism do both IValidator and form-level validation report problems to the user?
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