About Standard JSF Converters

Conversion is the process whereby component data is transformed from strings to Java objects and vice versa, depending on whether the data is being sent from the client browser to the application server, or from the server to the browser.

For example a date field in a web form might represent a java.util.Date object as a text string in the format pattern yyyy/mm/dd. When a user edits a date field and submits the form, the string must be converted back to the type that is required by the application.

The JavaServer Faces (JSF) implementation provides standard converters that handle conversion between strings and simple data types (e.g., numbers, Boolean). Implementing the javax.faces.convert.Converter interface, the supplied JSF converter classes are:

BigDecimalConverter
BigIntegerConverter
BooleanConverter
ByteConverter
CharacterConverter
DateTimeConverter
DoubleConverter
FloatConverter
IntegerConverter
LongConverter
NumberConverter
ShortConverter

Note: JSF automatically converts component data when the component value binding type is a primitive type, BigDecimal, or BigInteger. For Date values, you need to add an explicit converter because you can specify the formatting style to convert to for date and time portions.

Standard Converters and Their Tags

Two of the standard converter classes have their own tags, which let you specify the format and type of the component data by configuring the tag attributes. The standard converter classes that have their own tags are registered in JSF under a symbolic name:

Tag	Class	Name	For conversion between...
f:convertDateTime	`DateTimeConverter`	javax.faces.DateTime	String and `java.util.Date` values
f:convertNumber	`NumberConverter`	javax.faces.Number	String and `java.lang.Number` values

To use a standard tag, nest the supplied tag within a component. Use the tag's attributes to configure the format and type of component data.

For information about using standard tags, see Registering a Standard Converter on a Component Using a Standard Tag. For a list of the supported tag attributes, see Reference: Standard JSF Converter and Validator Tags.

Other Standard Converters That Do Not Have Supplied Tags

The rest of the built-in converters do not have their own tags. These standard converters are registered in JSF for a specific data type:

Type	Class	Name	For conversion between...
BigDecimal	`BigDecimalConverter`	javax.faces.BigDecimal	String and `java.math.BigDecimal` values
BigInteger	`BigIntegerConverter`	javax.faces.BigInteger	String and `java.math.BigInteger` values
Boolean and boolean	`BooleanConverter`	javax.faces.Boolean	String and `java.lang.Boolean` (and boolean primitive) values
Byte and byte	`ByteConverter`	javax.faces.Byte	String and `java.lang.Number` values
Character and char	`CharacterConverter`	javax.faces.Character	String and `java.lang.Character` (and char primitive) values
Double and double	`DoubleConverter`	javax.faces.Double	String and `java.lang.Double` (and double primitive) values
Float and float	`FloatConverter`	javax.faces.Float	String and `java.lang.Float` (and float primitive) values
Integer and int	`IntegerConverter`	javax.faces.Integer	String and `java.lang.Integer` (and int primitive) values
Long and long	`LongConverter`	javax.faces.Long	String and `java.lang.Long` (and long primitive) values
Short and short	`ShortConverter`	javax.faces.Short	String and `java.lang.Short` (and short primitive) values

You can use standard converters that do not have supplied tags in one of three ways:

Add the converter attribute to a component using the fully qualified class name or name of the converter as the value.
Nest the f:converter tag within a component. Use this tag's converterID attribute to reference the converter's name.

For information about using standard converters without standard tags, see Registering a Standard Converter That Does Not Have A Supplied Tag.

If you need to convert a component's data to a type other than a standard type supported in JSF, or when you want to convert the format of the data, you can create your own custom converter. See Working with Custom JSF Converters and Validators for information about creating and registering custom converters for your application.