About Custom JSF Converters

The standard converters supplied in the JavaServer Faces Reference Implementation provide the most common data type conversions. If you need to convert a component's data to a type other than a standard type, you can create your own custom converter.

It is beyond the scope of this topic to teach you how to write a custom converter. Briefly, a custom converter must implement the javax.faces.convert.Converter interface. In the custom implementation you must must define how component data is to be converted between String and an object of the desired type, and override the getAsObject and getAsString methods of the Converter interface. Use javax.faces.convert.ConverterException to throw the appropriate exceptions and javax.faces.application.FacesMessage to construct the corresponding error messages. For more information, see the Javadoc for javax.faces.convert.Converter, or go to the java.sun.com web page
http://java.sun.com/j2ee/javaserverfaces/

To use a custom converter in your application, you need to:

Register the custom converter in the application's JSF configuration file (faces-config.xml). You can register it under a converter identifier (ID) or a fully qualified class name for a specific data type.
Register the custom converter on a component that needs custom conversion. Use the converter attribute on the component or nest the f:converter tag within the component.

Note: If a custom converter is registered in an application under a class for a specific data type, whenever a component's value references a value binding (see code snippet below) that has the same type as the custom converter object, JSF will automatically use the converter of that class to convert the data. In that case you don't even have to use the converter attribute or the f:converter tag to register the custom converter on a component.

<h:inputText value="#{myBean.myProperty}"/>

where myProperty has the same type as the custom converter.