JSF Standard Converters

The JavaServer Faces provides a set of Converters. You can use that to convert component data. The purpose of conversion is to take the String-based data from the Servlet API and convert it to strongly typed Java objects.

The javax.faces.convert package contains all the standard converters. Converters are implicitly assigned based on the type of the EL expression pointed to by the value of the component. You can also access these converters by converter ID. The following table shows converter classes and their associated converter IDs.

JSF Converters

Class	Converter ID
BigDecimalConverter	javax.faces.BigDecimal
BigIntegerConverter	javax.faces.BigInteger
BooleanConverter	javax.faces.Boolean
ByteConverter	javax.faces.Byte
CharacterConverter	javax.faces.Character
DateTimeConverter	javax.faces.Datetime
DoubleConverter	javax.faces.Double
EnumConverter	javax.faces.Enum
FloatConverter	javax.faces.Float
IntegerConverter	javax.faces.Integer
LongConverter	javax.faces.Long
NumberConverter	javax.faces.Number
ShortConverter	javax.faces.Short

A standard error message is associated with each of the converters. If you are using any converter onto a component on your page and the converter is not able to convert the component's value, the converter's error message will display on the page.

The standard converters DateTimeConverter and NumberConverter both have their own tags, which allow you to configure the format of the component data by using the tag attributes.

JSF Data-Conversion Core Tags

Tag	Function
f:converter	It is used to add an arbitrary converter to the parent component.
f:convertDateTime	It is used to add a DateTimeConverter instance to the parent component.
f:convertNumber	It is used to adds a NumberConverter instance to the parent component.

JSF <f:converter> Tag Example

// index.xhtml

<h:form>
<h:outputLabel for="username">User Name</h:outputLabel>
<h:inputText id="user-id" value="#{user.name}"/><br/>
<h:outputLabel for="age">Enter Age</h:outputLabel>
<h:inputText id="age-id" value="#{user.age}">
<f:converter converterId="javax.faces.Integer" />
</h:inputText><br/>
<h:commandButton action="response.xhtml" value="Submit"/>
</h:form>

// User.java

import javax.faces.bean.ManagedBean;
import javax.faces.bean.RequestScoped;
@ManagedBean
@RequestScoped
public class User {
String name;
Integer age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
}  

// response.xhtml

<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://xmlns.jcp.org/jsf/html"
<h:head>
<title>Response Page</title>
</h:head>
<h:body>
<h1>
<h:outputText value="Hello #{user.name}"/>
</h1>
<h3><h:outputLabel value="You are #{user.age} years old."></h:outputLabel></h3>
</h:body>
</html>

Output:

// index page