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package javax.servlet.jsp.jstl.fmt;
import java.text.MessageFormat;
import java.util.Enumeration;
import java.util.Locale;
import java.util.MissingResourceException;
import java.util.ResourceBundle;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.jstl.core.Config;
/**
* Class which exposes the locale-determination logic for resource bundles
* through convenience methods.
*
* <p> This class may be useful to any tag handler implementation that needs
* to produce localized messages. For example, this might be useful for
* exception messages that are intended directly for user consumption on an
* error page.
*
* @author Jan Luehe
*/
public class LocaleSupport {
private static final String UNDEFINED_KEY = "???";
private static final char HYPHEN = '-';
private static final char UNDERSCORE = '_';
private static final String REQUEST_CHAR_SET =
"javax.servlet.jsp.jstl.fmt.request.charset";
private static final Locale EMPTY_LOCALE = new Locale("", "");
/**
* Retrieves the localized message corresponding to the given key.
*
* <p> The given key is looked up in the resource bundle of the default
* I18N localization context, which is retrieved from the
* <tt>javax.servlet.jsp.jstl.fmt.localizationContext</tt> configuration
* setting.
*
* <p> If the configuration setting is empty, or the default I18N
* localization context does not contain any resource bundle, or the given
* key is undefined in its resource bundle, the string "???<key>???" is
* returned, where "<key>" is replaced with the given key.
*
* @param pageContext the page in which to get the localized message
* corresponding to the given key
* @param key the message key
*
* @return the localized message corresponding to the given key
*/
public static String getLocalizedMessage(PageContext pageContext,
String key) {
return getLocalizedMessage(pageContext, key, null, null);
}
/**
* Retrieves the localized message corresponding to the given key.
*
* <p> The given key is looked up in the resource bundle with the given
* base name.
*
* <p> If no resource bundle with the given base name exists, or the given
* key is undefined in the resource bundle, the string "???<key>???" is
* returned, where "<key>" is replaced with the given key.
*
* @param pageContext the page in which to get the localized message
* corresponding to the given key
* @param key the message key
* @param basename the resource bundle base name
*
* @return the localized message corresponding to the given key
*/
public static String getLocalizedMessage(PageContext pageContext,
String key,
String basename) {
return getLocalizedMessage(pageContext, key, null, basename);
}
/**
* Retrieves the localized message corresponding to the given key, and
* performs parametric replacement using the arguments specified via
* <tt>args</tt>.
*
* <p> See the specification of the <fmt:message> action for a description
* of how parametric replacement is implemented.
*
* <p> The localized message is retrieved as in
* {@link #getLocalizedMessage(javax.servlet.jsp.PageContext,java.lang.String) getLocalizedMessage(pageContext, key)}.
*
* @param pageContext the page in which to get the localized message
* corresponding to the given key
* @param key the message key
* @param args the arguments for parametric replacement
*
* @return the localized message corresponding to the given key
*/
public static String getLocalizedMessage(PageContext pageContext,
String key,
Object[] args) {
return getLocalizedMessage(pageContext, key, args, null);
}
/**
* Retrieves the localized message corresponding to the given key, and
* performs parametric replacement using the arguments specified via
* <tt>args</tt>.
*
* <p> See the specification of the <fmt:message> action for a description
* of how parametric replacement is implemented.
*
* <p> The localized message is retrieved as in
* {@link #getLocalizedMessage(javax.servlet.jsp.PageContext,java.lang.String, java.lang.String) getLocalizedMessage(pageContext, key, basename)}.
*
* @param pageContext the page in which to get the localized message
* corresponding to the given key
* @param key the message key
* @param args the arguments for parametric replacement
* @param basename the resource bundle base name
*
* @return the localized message corresponding to the given key
*/
public static String getLocalizedMessage(PageContext pageContext,
String key,
Object[] args,
String basename) {
LocalizationContext locCtxt = null;
String message = UNDEFINED_KEY + key + UNDEFINED_KEY;
if (basename != null) {
locCtxt = getLocalizationContext(pageContext, basename);
} else {
locCtxt = getLocalizationContext(pageContext);
}
if (locCtxt != null) {
ResourceBundle bundle = locCtxt.getResourceBundle();
if (bundle != null) {
try {
message = bundle.getString(key);
if (args != null) {
MessageFormat formatter = new MessageFormat("");
if (locCtxt.getLocale() != null) {
formatter.setLocale(locCtxt.getLocale());
}
formatter.applyPattern(message);
message = formatter.format(args);
}
} catch (MissingResourceException mre) {
}
}
}
return message;
}
/**
* Gets the default I18N localization context.
*
* @param pc Page in which to look up the default I18N localization context
*/
private static LocalizationContext getLocalizationContext(PageContext pc) {
LocalizationContext locCtxt = null;
Object obj = Config.find(pc, Config.FMT_LOCALIZATION_CONTEXT);
if (obj == null) {
return null;
}
if (obj instanceof LocalizationContext) {
locCtxt = (LocalizationContext) obj;
} else {
// localization context is a bundle basename
locCtxt = getLocalizationContext(pc, (String) obj);
}
return locCtxt;
}
/**
* Gets the resource bundle with the given base name, whose locale is
* determined as follows:
*
* Check if a match exists between the ordered set of preferred
* locales and the available locales, for the given base name.
* The set of preferred locales consists of a single locale
* (if the <tt>javax.servlet.jsp.jstl.fmt.locale</tt> configuration
* setting is present) or is equal to the client's preferred locales
* determined from the client's browser settings.
*
* <p> If no match was found in the previous step, check if a match
* exists between the fallback locale (given by the
* <tt>javax.servlet.jsp.jstl.fmt.fallbackLocale</tt> configuration
* setting) and the available locales, for the given base name.
*
* @param pageContext Page in which the resource bundle with the
* given base name is requested
* @param basename Resource bundle base name
*
* @return Localization context containing the resource bundle with the
* given base name and the locale that led to the resource bundle match,
* or the empty localization context if no resource bundle match was found
*/
private static LocalizationContext getLocalizationContext(PageContext pc,
String basename) {
LocalizationContext locCtxt = null;
ResourceBundle bundle = null;
if ((basename == null) || basename.equals("")) {
return new LocalizationContext();
}
// Try preferred locales
Locale pref = getLocale(pc, Config.FMT_LOCALE);
if (pref != null) {
// Preferred locale is application-based
bundle = findMatch(basename, pref);
if (bundle != null) {
locCtxt = new LocalizationContext(bundle, pref);
}
} else {
// Preferred locales are browser-based
locCtxt = findMatch(pc, basename);
}
if (locCtxt == null) {
// No match found with preferred locales, try using fallback locale
pref = getLocale(pc, Config.FMT_FALLBACK_LOCALE);
if (pref != null) {
bundle = findMatch(basename, pref);
if (bundle != null) {
locCtxt = new LocalizationContext(bundle, pref);
}
}
}
if (locCtxt == null) {
// try using the root resource bundle with the given basename
try {
bundle = ResourceBundle.getBundle(basename, EMPTY_LOCALE,
Thread.currentThread().getContextClassLoader());
if (bundle != null) {
locCtxt = new LocalizationContext(bundle, null);
}
} catch (MissingResourceException mre) {
// do nothing
}
}
if (locCtxt != null) {
// set response locale
if (locCtxt.getLocale() != null) {
setResponseLocale(pc, locCtxt.getLocale());
}
} else {
// create empty localization context
locCtxt = new LocalizationContext();
}
return locCtxt;
}
/*
* Determines the client's preferred locales from the request, and compares
* each of the locales (in order of preference) against the available
* locales in order to determine the best matching locale.
*
* @param pageContext the page in which the resource bundle with the
* given base name is requested
* @param basename the resource bundle's base name
*
* @return the localization context containing the resource bundle with
* the given base name and best matching locale, or <tt>null</tt> if no
* resource bundle match was found
*/
private static LocalizationContext findMatch(PageContext pageContext,
String basename) {
LocalizationContext locCtxt = null;
// Determine locale from client's browser settings.
for (Enumeration enum_ = getRequestLocales(
(HttpServletRequest)pageContext.getRequest());
enum_.hasMoreElements(); ) {
Locale pref = (Locale) enum_.nextElement();
ResourceBundle match = findMatch(basename, pref);
if (match != null) {
locCtxt = new LocalizationContext(match, pref);
break;
}
}
return locCtxt;
}
/*
* Gets the resource bundle with the given base name and preferred locale.
*
* This method calls java.util.ResourceBundle.getBundle(), but ignores
* its return value unless its locale represents an exact or language match
* with the given preferred locale.
*
* @param basename the resource bundle base name
* @param pref the preferred locale
*
* @return the requested resource bundle, or <tt>null</tt> if no resource
* bundle with the given base name exists or if there is no exact- or
* language-match between the preferred locale and the locale of
* the bundle returned by java.util.ResourceBundle.getBundle().
*/
private static ResourceBundle findMatch(String basename, Locale pref) {
ResourceBundle match = null;
try {
ResourceBundle bundle =
ResourceBundle.getBundle(basename, pref,
Thread.currentThread().getContextClassLoader());
Locale avail = bundle.getLocale();
if (pref.equals(avail)) {
// Exact match
match = bundle;
} else {
/*
* We have to make sure that the match we got is for
* the specified locale. The way ResourceBundle.getBundle()
* works, if a match is not found with (1) the specified locale,
* it tries to match with (2) the current default locale as
* returned by Locale.getDefault() or (3) the root resource
* bundle (basename).
* We must ignore any match that could have worked with (2) or (3).
* So if an exact match is not found, we make the following extra
* tests:
* - avail locale must be equal to preferred locale
* - avail country must be empty or equal to preferred country
* (the equality match might have failed on the variant)
*/
if (pref.getLanguage().equals(avail.getLanguage())
&& ("".equals(avail.getCountry()) || pref.getCountry().equals(avail.getCountry()))) {
/*
* Language match.
* By making sure the available locale does not have a
* country and matches the preferred locale's language, we
* rule out "matches" based on the container's default
* locale. For example, if the preferred locale is
* "en-US", the container's default locale is "en-UK", and
* there is a resource bundle (with the requested base
* name) available for "en-UK", ResourceBundle.getBundle()
* will return it, but even though its language matches
* that of the preferred locale, we must ignore it,
* because matches based on the container's default locale
* are not portable across different containers with
* different default locales.
*/
match = bundle;
}
}
} catch (MissingResourceException mre) {
}
return match;
}
/*
* Returns the locale specified by the named scoped attribute or context
* configuration parameter.
*
* <p> The named scoped attribute is searched in the page, request,
* session (if valid), and application scope(s) (in this order). If no such
* attribute exists in any of the scopes, the locale is taken from the
* named context configuration parameter.
*
* @param pageContext the page in which to search for the named scoped
* attribute or context configuration parameter
* @param name the name of the scoped attribute or context configuration
* parameter
*
* @return the locale specified by the named scoped attribute or context
* configuration parameter, or <tt>null</tt> if no scoped attribute or
* configuration parameter with the given name exists
*/
private static Locale getLocale(PageContext pageContext, String name) {
Locale loc = null;
Object obj = Config.find(pageContext, name);
if (obj != null) {
if (obj instanceof Locale) {
loc = (Locale) obj;
} else {
loc = parseLocale((String) obj);
}
}
return loc;
}
/*
* Stores the given locale in the response object of the given page
* context, and stores the locale's associated charset in the
* javax.servlet.jsp.jstl.fmt.request.charset session attribute, which
* may be used by the <requestEncoding> action in a page invoked by a
* form included in the response to set the request charset to the same as
* the response charset (this makes it possible for the container to
* decode the form parameter values properly, since browsers typically
* encode form field values using the response's charset).
*
* @param pageContext the page context whose response object is assigned
* the given locale
* @param locale the response locale
*/
private static void setResponseLocale(PageContext pc, Locale locale) {
// set response locale
ServletResponse response = pc.getResponse();
response.setLocale(locale);
// get response character encoding and store it in session attribute
if (pc.getSession() != null) {
try {
pc.setAttribute(REQUEST_CHAR_SET,
response.getCharacterEncoding(),
PageContext.SESSION_SCOPE);
} catch (IllegalStateException ex) {} // invalidated session ignored
}
}
/**
* See parseLocale(String, String) for details.
*/
private static Locale parseLocale(String locale) {
return parseLocale(locale, null);
}
/**
* Parses the given locale string into its language and (optionally)
* country components, and returns the corresponding
* <tt>java.util.Locale</tt> object.
*
* If the given locale string is null or empty, the runtime's default
* locale is returned.
*
* @param locale the locale string to parse
* @param variant the variant
*
* @return <tt>java.util.Locale</tt> object corresponding to the given
* locale string, or the runtime's default locale if the locale string is
* null or empty
*
* @throws IllegalArgumentException if the given locale does not have a
* language component or has an empty country component
*/
private static Locale parseLocale(String locale, String variant) {
Locale ret = null;
String language = locale;
String country = null;
int index = -1;
if (((index = locale.indexOf(HYPHEN)) > -1)
|| ((index = locale.indexOf(UNDERSCORE)) > -1)) {
language = locale.substring(0, index);
country = locale.substring(index+1);
}
if ((language == null) || (language.length() == 0)) {
throw new IllegalArgumentException(
"Missing language component in 'value' attribute in setLocale");
}
if (country == null) {
if (variant != null)
ret = new Locale(language, "", variant);
else
ret = new Locale(language, "");
} else if (country.length() > 0) {
if (variant != null)
ret = new Locale(language, country, variant);
else
ret = new Locale(language, country);
} else {
throw new IllegalArgumentException(
"Empty country component in 'value' attribute in setLocale");
}
return ret;
}
/**
* HttpServletRequest.getLocales() returns the server's default locale
* if the request did not specify a preferred language.
* We do not want this behavior, because it prevents us from using
* the fallback locale.
* We therefore need to return an empty Enumeration if no preferred
* locale has been specified. This way, the logic for the fallback
* locale will be able to kick in.
*/
private static Enumeration getRequestLocales(HttpServletRequest request) {
Enumeration values = request.getHeaders("accept-language");
if (values.hasMoreElements()) {
// At least one "accept-language". Simply return
// the enumeration returned by request.getLocales().
// System.out.println("At least one accept-language");
return request.getLocales();
} else {
// No header for "accept-language". Simply return
// the empty enumeration.
// System.out.println("No accept-language");
return values;
}
}
}
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