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:

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...
String and java.util.Date values
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
String and java.math.BigDecimal values
BigInteger BigIntegerConverter
String and java.math.BigInteger values
Boolean and boolean BooleanConverter
String and java.lang.Boolean (and boolean primitive) values
Byte and byte ByteConverter
String and java.lang.Number values
Character and char CharacterConverter
String and java.lang.Character (and char primitive) values
Double and double DoubleConverter
String and java.lang.Double (and double primitive) values
Float and float FloatConverter
String and java.lang.Float (and float primitive) values
Integer and int IntegerConverter
String and java.lang.Integer (and int primitive) values
Long and long LongConverter
String and java.lang.Long (and long primitive) values
Short and short ShortConverter
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:

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.

About the Conversion and Validation Process in JSF
About Conversion and Validation Errors
About the converter Attribute
Working with Standard JSF Converters and Validators