The Validator tag registers a named Validator instance on the component associated with the enclosing tag. The JavaServer Faces framework includes three standard validators (see the validateDoubleRange, validateLength, and validateLongRange tags) but the Validator interface can be implemented by classes that provide custom validation for your application. This tag accepts one value matching the validator ID you assigned to your validator class in your Faces configuration file. The body content of this tag must be empty.

Example:

<h:inputText id="emailAddress" value="#{customerBean.customer.emailAddress}">
  <f:validator validatorId="emailAddressValidator" />
</h:inputText> 
<h:message for="emailAddress" />

HTML Output

<input id="form:emailAddress" name="form:emailAddress" type="text" value="fake@email"/>
Invalid email address.