Incorporating Validation into the User Interface
ADF Faces provides the following types of validation:
UI component attributes: ADF Faces input components have attributes that can be used to validate data. For example you can set the required attribute on a component to specify whether a value must be entered. When set to true, the component must have a value.
Default ADF Faces validators: The standard validators supplied by ADF Faces and the JSF reference implementation provide common validation checks, such as validating date ranges, and validating the length of entered data.
Custom ADF Faces validators: You can create your own validators and then select them to be used in conjunction with UI components.
You can use UI validation to provide immediate feedback and meaningful error messages to users. However, UI validation should always have equivalent validation at the business services layer, so that the same validation is applied when the model is exposed in other ways.