Creating Custom UI Components and Other Custom Objects - The Java EE 6 Tutorial: Advanced Topics - page 131

requiredMessage="#{bundle.ReqCreditCard}" >
<f:converter converterId="ccno"/>
<f:validateRegex
pattern="\d{16}|\d{4} \d{4} \d{4} \d{4}|\d{4}-\d{4}-
\d{4}-\d{4}" />
</h:inputText>
• Bind the Converter implementation to a managed bean property using the
f:converter tag's binding attribute, as described in “ Binding Converters,
Listeners, and Validators to Managed Bean Properties ” on page 138 .
The JavaServer Faces implementation calls the converter's getAsObject method to
strip spaces and hyphens from the input value. The getAsString method is called
when the bookcashier.xhtml page is redisplayed; this happens if the user orders
more than $100 worth of books.
In the Duke's Tutoring case study, each converter is registered as the converter for a par-
ticular class. The converter is automatically invoked whenever that class is specified by a
value attribute of an input component. In the following example, the itemValue at-
tribute (highlighted in bold) calls the converter for the Guardian class:
Click here to view code image
<h:selectManyListbox id="selectGuardiansMenu"
value="#{guardianManager.selectedGuardians}"
size="5">
<f:selectItems value="#{guardianManager.allGuardians}"
var="selectedGuardian"
itemLabel="#{selectedGuardian.name}"
itemValue="#{selectedGuardian}" />
</h:selectManyListbox>
Creating and Using a Custom Validator
If the standard validators or Bean Validation don't perform the validation checking you
need, you can create a custom validator to validate user input. As explained in “ Validation
Model ” on page 63 , there are two ways to implement validation code:
• Implement a managed bean method that performs the validation.
• Provide an implementation of the javax.faces.validator.Validator
interface to perform the validation.
“Writing a Method to Perform Validation” in The Java EE 6 Tutorial: Basic Concepts ex-
plains how to implement a managed bean method to perform validation. The rest of this
section explains how to implement the Validator interface.