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Using the Standard Converters

The JavaServer Faces implementation provides a set of Converter implementations that you can use to convert component data. For more information on the conceptual details of the conversion model, see Conversion Model.

The standard Converter implementations, located in the javax.faces.convert package, are as follows:

Two of these standard converters (DateTimeConverter and NumberConverter) have their own tags, which allow you to configure the format of the component data by configuring the tag attributes. Using DateTimeConverter discusses using DateTimeConverter. Using NumberConverter discusses using NumberConverter.

You can use the other standard converters in one of three ways:

The latter two will convert the component's local value. The first method will convert the model value of the component. For example, if you want a component's data to be converted to an Integer, you can bind the component to a property similar to this:

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

Alternatively, if the component is not bound to a bean property, you can use the converter attribute on the component tag:

<h:inputText value="#{LoginBean.Age}"
  converter="javax.faces.convert.IntegerConverter" /> 

The data corresponding to this tag will be converted to a java.lang.Integer. Notice that 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 other converters will suffice, you can simply reference that converter using the component tag's converter attribute.

Finally, you can nest a converter tag within the component tag and refer to the converter's ID via the converter tag's converterId attribute. If the tag is referring to a custom converter, the value of converterID must match the ID in the application configuration resource file. Here is an example:

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

Using DateTimeConverter

You can convert a component's data to a java.util.Date by nesting the convertDateTime tag inside the component tag. The convertDateTime tag has several attributes that allow you to specify the format and type of the data. Table 18-5 lists the attributes.

Here is a simple example of a convertDateTime tag from the bookreceipt.jsp page:

<h:outputText value="#{cashier.shipDate}">
  <f:convertDateTime dateStyle="full" />
</h:outputText> 

Here is an example of a date and time that this tag can display:

Saturday, Feb 22, 2003 

You can also display the same date and time using this tag:

<h:outputText value="#{cashier.shipDate}">
  <f:convertDateTime 
    pattern="EEEEEEEE, MMM d, yyyy"
</h:outputText> 

If you want to display the example date in Spanish, you can use the parseLocale attribute:

<h:inputText value="#{cashier.shipDate}">
  <f:convertDateTime dateStyle="full" 
    parseLocale="Locale.SPAIN"
    timeStyle="long" type="both" />
</h:inputText> 

This tag would display

Sabado, Feb 22, 2003 

Please refer to the Customizing Formats lesson of the Java Tutorial at
http://java.sun.com/docs/books/tutorial/i18n/format/simpleDateFormat.html for more information on how to format the output using the pattern attribute of the convertDateTime tag.

Table 18-5 convertDateTime Tag Attributes 
Attribute
Type
Description
dateStyle
String
Defines the format, as specified by java.text.DateFormat, of a date or the date part of a date string. Applied only if type is date (or both) and pattern is not defined. Valid values: default, short, medium, long, and full. If no value is specified, default is used.
parseLocale
String or Locale
Locale whose predefined styles for dates and times are used during formatting or parsing. If not specified, the Locale returned by FacesContext.getLocale will be used.
pattern
String
Custom formatting pattern that determines how the date/time string should be formatted and parsed. If this attribute is specified, dateStyle, timeStyle, and type attributes are ignored.
timeStyle
String
Defines the format, as specified by java.text.DateFormat, of a time or the time part of a date string. Applied only if type is time and pattern is not defined. Valid values: default, short, medium, long, and full. If no value is specified, default is used.
timeZone
String or TimeZone
Time zone in which to interpret any time information in the date string.
type
String
Specifies whether the string value will contain a date, a time, or both. Valid values are date, time, or both. If no value is specified, date is used.

Using NumberConverter

You can convert a component's data to a java.lang.Number by nesting the convertNumber tag inside the component tag. The convertNumber tag has several attributes that allow you to specify the format and type of the data. Table 18-6 lists the attributes.

The bookcashier.jsp page of Duke's Bookstore uses a convertNumber tag to display the total prices of the books in the shopping cart:

<h:outputText value="#{cart.total}" >
  <f:convertNumber type="currency"
</h:outputText> 

Here is an example of a number this tag can display

$934 

This number can also be displayed using this tag:

<h:outputText id="netIncome" 
  value="#{cart.Total}" >
  <f:convertNumber pattern="$####" />
</h:outputText> 

Please refer to the Customizing Formats lesson of the Java Tutorial at
http://java.sun.com/docs/books/tutorial/i18n/format/decimalFormat.html for more information on how to format the output using the pattern attribute of the convertNumber tag.

Table 18-6 convertNumber Attributes  
Attribute
Type
Description
currencyCode
String
ISO4217 currency code, used only when formatting currencies.
currencySymbol
String
Currency symbol, applied only when formatting currencies.
groupingUsed
boolean
Specifies whether formatted output contains grouping separators.
integerOnly
boolean
Specifies whether only the integer part of the value will be parsed.
maxFractionDigits
int
Maximum number of digits formatted in the fractional part of the output.
maxIntegerDigits
int
Maximum number of digits formatted in the integer part of the output
minFractionDigits
int
Minimum number of digits formatted in the fractional part of the output.
minIntegerDigits
int
Minimum number of digits formatted in the integer part of the output
parseLocale
String or Locale
Locale whose number styles are used to format or parse data.
pattern
String
Custom formatting pattern that determines how the number string is formatted and parsed.
type
String
Specifies whether the string value is parsed and formatted as a number, currency, or percentage. If not specified, number is used.

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