This Chapter
-	Chapter 7: JSTL
-	Introducing JSTL
-	General-Purpose Actions
-	Conditional Actions
-	Iterator Actions
-	Formatting Actions
-	Functions
-	Summary

Table of Contents
-	Introduction
-	Chapter 1: Model 2 and Struts
-	Chapter 2: Input Validation with Action Forms
-	Chapter 3: The HTML Tag Library
-	Chapter 4: Input Validation and Data Conversion
-	Chapter 5: The Validator Plugin
-	Chapter 6: The Expression Language
-	Chapter 7: JSTL
-	Chapter 8: The Bean Tag Library
-	Chapter 9: The Logic Tag Library
-	Chapter 10: Struts-EL, Nested, selectLabel
-	Chapter 11: Message Handling and Internationalization
-	Chapter 12: The Tiles Framework
-	Chapter 13: Securing Struts Applications
-	Chapter 14: The Config Object
-	Chapter 15: The Persistence Layer
-	Chapter 16: Object Caching
-	Chapter 17: File Upload and File Download
-	Chapter 18: Paging and Sorting
-	Chapter 19: Preventing Double Submits
-	Chapter 20: Early HttpSession Invalidation
-	Chapter 21: Decorating Request Objects
-	Chapter 22: How Struts Works

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Formatting Actions

JSTL provides tags for formatting and parsing numbers and dates. The tags are formatNumber, formatDate, timeZone, setTimeZone, parseNumber, and parseDate. These tags are discussed in the sections to follow.

The formatNumber Tag

You use formatNumber to format numbers. This tag gives you the flexibility of using its various attributes to get a format that suits your need. The syntax of formatNumber has two forms. The first is used without a body content:

<fmt:formatNumber value="numericValue"
  [type="{number|currency|percent}"]
  [pattern="customPattern"]
  [currencyCode="currencyCode"]
  [currencySymbol="currencySymbol"]
  [groupingUsed="{true|false}"]
  [maxIntegerDigits="maxIntegerDigits"]
  [minIntegerDigits="minIntegerDigits"]
  [maxFractionDigits="maxFractionDigits"]
  [minFractionDigits="minFractionDigits"]
  [var="varName"]
  [scope="{page|request|session|application}"]/>

The second form is used with a body content:

<fmt:formatNumber [type="{number|currency|percent}"]
  [pattern="customPattern"]
  [currencyCode="currencyCode"]
  [currencySymbol="currencySymbol"]
  [groupingUsed="{true|false}"]
  [maxIntegerDigits="maxIntegerDigits"]
  [minIntegerDigits="minIntegerDigits"]
  [maxFractionDigits="maxFractionDigits"]
  [minFractionDigits="minFractionDigits"]
  [var="varName"]
  [scope="{page|request|session|application}"]>
  numeric value to be formatted
</fmt:formatNumber>

The body content is JSP. The list of the formatNumber tag’s attributes is given in Table 7.8.

Table 7.8: The formatNumber tag’s attributes

One of the uses of formatNumber is to format numbers as currencies. For this, you can use the currencyCode attribute to specify an ISO 4217 currency code. Some of the codes are given in Table 7.9.

Table 7.9: ISO 4217 Currency Codes

The examples of how to use formatNumber are given in Table 7.10.

Table 7.10: Using the formatNumber tag

Note that when formatting currencies, if the currencyCode attribute is not specified, the client browser's locale is used.

The formatDate Tag

You use the formatDate tag to format dates. The syntax is as follows:

<fmt:formatDate value="date"
  [type="{time|date|both}"]
  [dateStyle="{default|short|medium|long|full}"]
  [timeStyle="{default|short|medium|long|full}"]
  [pattern="customPattern"]
  [timeZone="timeZone"]
  [var="varName"]
  [scope="{page|request|session|application}"]/>

The body content is JSP. The list of the formatDate tag’s attributes is given in Table 7.11.

For possible values of the timeZone attribute, see the section, “The timeZone Tag”.

The following code uses the formatDate tag to format the java.util.Date object referenced by the scoped variable now.

Default: <fmt:formatDate value="${now}"/>
Short: <fmt:formatDate value="${now}" dateStyle="short"/>
Medium: <fmt:formatDate value="${now}" dateStyle="medium"/>
Long: <fmt:formatDate value="${now}" dateStyle="long"/>
Full: <fmt:formatDate value="${now}" dateStyle="full"/>

The following formatDate tags are used to format times.

Default: <fmt:formatDate type="time" value="${now}"/>
Short: <fmt:formatDate type="time" value="${now}"
  timeStyle="short"/>
Medium: <fmt:formatDate type="time" value="${now}"
  timeStyle="medium"/>
Long: <fmt:formatDate type="time" value="${now}" timeStyle="long"/>
Full: <fmt:formatDate type="time" value="${now}" timeStyle="full"/>

The following formatDate tags format both dates and times.

Default: <fmt:formatDate type="both" value="${now}"/>
Short date short time: <fmt:formatDate type="both"
  value="${now}" dateStyle="short" timeStyle="short"/>
Long date long time format: <fmt:formatDate type="both"
  value="${now}" dateStyle="long" timeStyle="long"/>

The following formatDate tags are used to format times with time zones.

Time zone CT: <fmt:formatDate type="time" value="${now}"
  timeZone="CT"/><br/>
Time zone HST: <fmt:formatDate type="time" value="${now}"
  timeZone="HST"/><br/>

The following formatDate tags are used to format dates and times using custom patterns.

<fmt:formatDate type="both" value="${now}" pattern="dd.MM.yy"/>
<fmt:formatDate type="both" value="${now}" pattern="dd.MM.yyyy"/>

The timeZone Tag

The timeZone tag is used to specify the time zone in which time information is to be formatted or parsed in its body content. The syntax is as follows:

<fmt:timeZone value="timeZone">
  body content
</fmt:timeZone>

The body content is JSP. The attribute value can be passed a dynamic value of type String or java.util.TimeZone. The values for US and Canada time zones are given in Table 7.12.

If the value attribute is null or empty, the GMT time zone is used.

<fmt:timeZone value="GMT+1:00">
  <fmt:formatDate value="${now}" type="both" dateStyle="full"
  timeStyle="full"/>
</fmt:timeZone>
<fmt:timeZone value="HST">
  <fmt:formatDate value="${now}" type="both" dateStyle="full"
  timeStyle="full"/>
</fmt:timeZone>
<fmt:timeZone value="CST">
  <fmt:formatDate value="${now}" type="both" dateStyle="full"
  timeStyle="full"/>
</fmt:timeZone>

Table 7.12: US and Canada Time Zones

The setTimeZone Tag

You use the setTimeZone tag to store the specified time zone in a scoped variable or the time configuration variable. The syntax of setTimeZone is as follows:

<fmt:setTimeZone value="timeZone" [var="varName"]
  [scope="{page|request|session|application}"]/>

Table 7.13 presents the setTimeZone tag’s attributes.

Table 7.13: The setTimeZone tag’s attributes

The parseNumber Tag

You use parseNumber to parse a string representation of a number, a currency, or a percentage in a locale-sensitive format into a number. The syntax has two forms. The first form is used without a body content:

<fmt:parseNumber value="numericValue"
  [type="{number|currency|percent}"]
  [pattern="customPattern"]
  [parseLocale="parseLocale"]
  [integerOnly="{true|false}"]
  [var="varName"]
  [scope="{page|request|session|application}"]/>

The second form is used with a body content:

<fmt:parseNumber [type="{number|currency|percent}"]
  [pattern="customPattern"]
  [parseLocale="parseLocale"]
  [integerOnly="{true|false}"]
  [var="varName"]
  [scope="{page|request|session|application}"]>
  numeric value to be parsed
  </fmt:parseNumber>

The content body is JSP. The parseNumber tag’s attributes are given in Table 7.14.

As an example, the following parseNumber tag parses the value referenced by the scoped variable quantity and stores the result in the formattedNumber scoped variable.

<fmt:parseNumber var="formattedNumber" type="number"
  value="${quantity}"/>

Table 7.14: The parseNumber tag’s attributes

The parseDate Tag

parseDate parses the string representation of a date and time in locale-sensitive format. The syntax has two forms. The first form is used without a body content:

<fmt:parseDate value="dateString"
  [type="{time|date|both}"]
  [dateStyle="{default|short|medium|long|full}"]
  [timeStyle="{default|short|medium|long|full}"]
  [pattern="customPattern"]
  [timeZone="timeZone"]
  [parseLocale="parseLocale"]
  [var="varName"]
  [scope="{page|request|session|application}"]/>

The second form is used with a body content:

<fmt:parseDate [type="{time|date|both}"]
  [dateStyle="{default|short|medium|long|full}"]
  [timeStyle="{default|short|medium|long|full}"]
  [pattern="customPattern"]
  [timeZone="timeZone"]
  [parseLocale="parseLocale"]
  [var="varName"]
  [scope="{page|request|session|application}"]>
  date value to be parsed
</fmt:parseDate>

The body content is JSP. Table 7.15 lists the parseDate tag’s attributes.

Table 7.15: The parseDate tag’s attributes

As an example, the following parseDate tag parses a date referenced by the scoped variable myDate and stores the resulting java.util.Date in a page-scoped variable formattedDate.

<c:set var="myDate" value="12/12/2005"/>
<fmt:parseDate var="formattedDate" type="date"
  dateStyle="short" value="${myDate}"/>

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