Validation and presentation of user inputs is essential for a good web user interface. The Calyxo Forms component offers a rich set of important features in this area:
- The conversion of validated input data into appropriate data types, ready for subsequent use.
- The generation of pregnant error messages for non-validated inputs.
- Marking of those input fields, that contain non-validated inputs
- I18n-aware validation, data formatting and error messages.
- Formatting of validated inputs according to common standards.
- Flexible validation rules for single fields as well as conditions involving mutiple fields.
Form validation is performed in two phases. First, every input is undergoing a sequence of field validations. Then, assertions can be used to test for complex conditions. Assert expressions use the JSP Expression Language (EL) and may reference any form field values.
A form validation succeeds, if all form inputs could be validated
and no assertions failed.
After a form has been validated successfully, a form data object, associated with the form, is populated with the validated data. The form data object may be accessed in subsequent request processing, eg in an action.