JSF Under the Hood—Part 2 - JSF and HTML5 - page 64

As shown in the Converter interface, it contains two APIs:
The first API is getAsObject , which performs the String-to-Object conversion; this API can be called in the
Process Validations phase (or the Apply Request Values phase). It has three parameters:
1. context , which represents the JSF FacesContext instance of this request.
2. component , which represents the component whose value will be converted.
This component instance can be used in order to retrieve the component attributes
if the converter needs to use them.
3. value , which represents the String value to be converted to Object .
The second API is getAsString , which performs the Object-to-String conversion; this API is called in the Render
Response phase. It takes three parameters:
1. context , which represents the JSF FacesContext instance of this request.
2. component , which represents the component whose value will be converted.
This component instance can be used in order to retrieve the component attributes
if the converter needs to use them.
3. value , which represents the Object value to be converted to String .
Every component can have one or more converter(s). If conversion could not be performed due to an error,
the converter must throw ConverterException ; in this case, the component that owns the converter will be marked
as invalid, and ConverterException message will be received and added to FacesContext messages in order to be
displayed by the <h:message> and <h:messages> components. Listing 3-2 shows an example illustrating how JSF
conversion works for multiple ValueHolder components with attached converters.
Listing 3-2. Conversion Example for Multiple ValueHolder Components
<h:form>
<h1>Test form</h1>
<h:outputText value="Enter First Number: "/>
<h:inputText id="firstNumber"
value="#{testBean.firstNumber}">
<f:convertNumber/>
</h:inputText>
<h:message for="firstNumber"/>
<br/>
<h:outputText value="Enter Second Number: "/>
<h:inputText id="secondNumber"
value="#{testBean.secondNumber}">
<f:convertNumber/>
</h:inputText>
<h:message for="secondNumber"/>
<br/>
<h:commandButton value="submit"/>
</h:form>
In this example, we have a form that contains two inputText components. Every inputText component has an
attached <f:convertNumber> converter. <f:convertNumber/> converter converts the user's entered value in the input
text to a Java Number object, which is then binded with the attribute ( firstNumber and secondNumber) of TestBean
managed bean. If the user enters non-numeric values in both inputText components and then clicks the "submit"
button, the user will see two conversion error messages in both the <h:message/> components which are attached to