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JSTL I18N Library
JSTL provides the following tags for displaying and formatting internationalized messages: setLocale, bundle, setBundle, message, param, and requestEncoding. Each of these tags is explained in a subsection below. See also Chapter 7 on JSTL in general.
setLocale
The setLocale tag is used to set the locale for the scope specified in the scope attribute of this tag. For example, if the scope is session, the specified locale applies to all JSPs in the same user session. If no locale is explicitly specified using setLocale, the locale found in the user request will be used.
The locale set using setLocale is used by the bundle and setBundle tags to select a ResourceBundle. The setLocale tag persists the locale by storing a Locale object referenced by the scoped variable javax.servlet.jsp.jstl.fmt.locale in the specified scope. The bundle and setBundle tags look for a scoped variable having the same name to determine the current locale. If no javax.servlet.jsp.jstl.fmt.locale scoped variable is found, the user's locale is used.
The syntax of setLocale is as follows:
<fmt:setLocale value="locale"
[variant="variant"]
[scope="{page|request|session|application}"]/>
The attributes for <fmt:setLocale> are described in Table 11.3.
| Attribute | Type | Description |
|---|---|---|
| value | java.lang.String or java.util.Locale | A string representation of a locale or a locale. If a String is used, it must be a two-letter ISO 639 language code, optionally followed by an underscore and an ISO 3166 country code. |
| variant | String | vendor- or browser-specific variant. |
| scope | String | The scope of the locale configuration variable. |
Table 11.3: The setLocale tag’s attributes
For example, the following setLocale tag sets the locale to English (United States) for the current session:
<fmt:setLocale value="en_US" scope="session"/>
bundle
The bundle tag loads a ResourceBundle based on the current locale. The ResourceBundle can then be used from inside this tag’s body.
The bundle tag has the following syntax:
<fmt:bundle basename="basename" [prefix="prefix"]> body content </fmt:bundle>
The attributes for the bundle tag are listed in Table 11.4.
| Attribute | Type | Description |
|---|---|---|
| basename | String | The base name for the ResourceBundle |
| prefix | String | The prefix to be prepended to the value of the message key of any nested message tag. |
Table 11.4: The bundle tag’s attributes
The following is an example of the bundle tag, used with a message tag as its body content:
<fmt:bundle basename="AppResources"> <fmt:message key="farewell"/> </fmt:bundle>
setBundle
setBundle is used to load a ResourceBundle and is similar to bundle. However, setBundle applies to all JSPs in the scope specified in the scope attribute of this tag. A message tag does not have to reside in its body content to use the ResourceBundle it loaded.
The following is the syntax of the setBundle tag:
<fmt:setBundle basename="basename"
[var="varName"]
[scope="{page|request|session|application}"]/>
The attributes for setBundle are listed in Table 11.5.
| Attribute | Type | Description |
|---|---|---|
| basename | String | The base name for the ResourceBundle |
| var | String | The name of the scoped variable that can be referenced in a message tag to use the ResourceBundle loaded by this tag. |
| scope | String | The scope for var |
Table 11.5: The setBundle tag’s attributes
Here is an example of how to use setBundle:
<fmt:setBundle basename="AppResources"/> <fmt:message key="welcome"/>
message
The message tag is used to read a message from the specified or current ResourceBundle and display the message. Its syntax has three forms. The first form is used without body content:
<fmt:message key="messageKey"
[bundle="resourceBundle"]
[var="varName"]
[scope="{page|request|session|application}"]/>
The second form is used with a body to specify message parameters:
<fmt:message key="messageKey"
[bundle="resourceBundle"]
[var="varName"]
[scope="{page|request|session|application}"]>
<fmt:param> subtags
</fmt:message>
The third form is used with a body to specify key and optional message parameters:
<fmt:message [bundle="resourceBundle"]
[var="varName"]
[scope="{page|request|session|application}"]>
key
optional <fmt:param> subtags
</fmt:message>
The list of attributes is given in Table 11.6.
| Attribute | Type | Description |
|---|---|---|
| key | String | The key of the message in the ResourceBundle |
| bundle | LocalizationContext | The name of the scoped variable that can be referenced in a message tag to use the ResourceBundle loaded by this tag. |
| var | String | The name of the scoped variable to store the obtained localized message |
| scope | String | The scope for var. |
Table 11.6: The message tag’s attributes
Here is an example of the message tag:
<fmt:setBundle basename="AppResources"/> <fmt:message key="welcome"/>
param
The param tag is used to pass a parameter to the enclosing message tag. Its syntax has two forms. The first form specifies the value via the value attribute:
<fmt:param value="messageParameter"/>
The second form specifies the value through the body content:
<fmt:param> body content </fmt:param>
The value attribute is the argument used for the replacement of a part in a localized message. It can be assigned a dynamic value of type java.lang.Object.
As an example, here is a param tag:
<fmt:message key="welcome"> <fmt:param value=”time”/> </fmt:message>
requestEncoding
This tag is used to set the encoding of the current HttpServletRequest object. Here is its syntax:
<fmt:requestEncoding [value=”charsetName”]/>
The value attribute is the name of character encoding to be applied when decoding request parameters. It can be assigned a dynamic value of type String.