Converting a Component’s Value

To use a particular converter to convert a component’s value, you need to register the converter onto the component. You can register any of the standard converters in one of the following four ways:

• Nest one of the standard converter tags inside the component’s tag. These tags are convertDateTime and convertNumber, which are described in Using DateTimeConverterand Using NumberConverter, respectively.

• Bind the value of the component to a backing bean property of the same type as the converter.

• Refer to the converter from the component tag’s converter attribute.

• Nest a converter tag inside of the component tag and use either the converter tag’s converterId attribute or its binding attribute to refer to the converter.

As an example of the second way, if you want a component’s data to be converted to an Integer, you can simply bind the component’s value to a backing bean property. Here is an example:

Integer age = 0;
public Integer getAge(){ return age;}
public void setAge(Integer age) {this.age = age;}

If the component is not bound to a bean property, you can employ the third method by using the converter attribute directly on the component tag:

<h:inputText
    converter="javax.faces.convert.IntegerConverter" />

This example shows the converter attribute referring to the fully-qualified class name of the converter. The converter attribute can also take the ID of the component.

The data from inputText tag in the this example will be converted to a java.lang.Integer. The Integer type is already a supported type of the NumberConverter. If you don’t need to specify any formatting instructions using the convertNumber tag attributes, and if one of the standard converters will suffice, you can simply reference that converter by using the component tag’s converter attribute.

Finally, you can nest a converter tag within the component tag and use either the converter tag’s converterId attribute or its binding attribute to reference the converter.

The converterId attribute must reference the converter’s ID. Here is an example:

<h:inputText value="#{LoginBean.Age}" />
    <f:converter converterId="Integer" />
</h:inputText>

Instead of using the converterId attribute, the converter tag can use the binding attribute. The binding attribute must resolve to a bean property that accepts and returns an appropriate Converter instance.

Custom converters and using binding attribute are advanced topics covered in Java EE 6 Tutorial, Volume II: Advanced Topics.