StringManager.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.catalina.tribes.util;
import java.text.MessageFormat;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Locale;
import java.util.Map;
import java.util.MissingResourceException;
import java.util.ResourceBundle;
/**
* An internationalization / localization helper class which reduces the bother of handling ResourceBundles and takes
* care of the common cases of message formatting which otherwise require the creation of Object arrays and such.
* <p>
* The StringManager operates on a package basis. One StringManager per package can be created and accessed via the
* getManager method call.
* <p>
* The StringManager will look for a ResourceBundle named by the package name given plus the suffix of "LocalStrings".
* In practice, this means that the localized information will be contained in a LocalStrings.properties file located in
* the package directory of the classpath.
* <p>
* Please see the documentation for java.util.ResourceBundle for more information.
*
* @author James Duncan Davidson [duncan@eng.sun.com]
* @author James Todd [gonzo@eng.sun.com]
* @author Mel Martinez [mmartinez@g1440.com]
*
* @see java.util.ResourceBundle
*/
public class StringManager {
private static int LOCALE_CACHE_SIZE = 10;
/**
* The ResourceBundle for this StringManager.
*/
private final ResourceBundle bundle;
private final Locale locale;
/**
* Creates a new StringManager for a given package. This is a private method and all access to it is arbitrated by
* the static getManager method call so that only one StringManager per package will be created.
*
* @param packageName Name of package to create StringManager for.
*/
private StringManager(String packageName, Locale locale) {
String bundleName = packageName + ".LocalStrings";
ResourceBundle bnd = null;
try {
bnd = ResourceBundle.getBundle(bundleName, locale);
} catch (MissingResourceException ex) {
// Try from the current loader (that's the case for trusted apps)
// Should only be required if using a TC5 style classloader structure
// where common != shared != server
ClassLoader cl = Thread.currentThread().getContextClassLoader();
if (cl != null) {
try {
bnd = ResourceBundle.getBundle(bundleName, locale, cl);
} catch (MissingResourceException ex2) {
// Ignore
}
}
}
bundle = bnd;
// Get the actual locale, which may be different from the requested one
if (bundle != null) {
Locale bundleLocale = bundle.getLocale();
if (bundleLocale.equals(Locale.ROOT)) {
this.locale = Locale.ENGLISH;
} else {
this.locale = bundleLocale;
}
} else {
this.locale = null;
}
}
/**
* Get a string from the underlying resource bundle or return null if the String is not found.
*
* @param key to desired resource String
*
* @return resource String matching <i>key</i> from underlying bundle or null if not found.
*
* @throws IllegalArgumentException if <i>key</i> is null
*/
public String getString(String key) {
if (key == null) {
String msg = "key may not have a null value";
throw new IllegalArgumentException(msg);
}
String str = null;
try {
// Avoid NPE if bundle is null and treat it like an MRE
if (bundle != null) {
str = bundle.getString(key);
}
} catch (MissingResourceException mre) {
// bad: shouldn't mask an exception the following way:
// str = "[cannot find message associated with key '" + key +
// "' due to " + mre + "]";
// because it hides the fact that the String was missing
// from the calling code.
// good: could just throw the exception (or wrap it in another)
// but that would probably cause much havoc on existing
// code.
// better: consistent with container pattern to
// simply return null. Calling code can then do
// a null check.
str = null;
}
return str;
}
/**
* Get a string from the underlying resource bundle and format it with the given set of arguments.
*
* @param key The key for the required message
* @param args The values to insert into the message
*
* @return The requested string formatted with the provided arguments
*/
public String getString(final String key, final Object... args) {
String value = getString(key);
if (value == null) {
value = key;
}
MessageFormat mf = new MessageFormat(value);
mf.setLocale(locale);
return mf.format(args, new StringBuffer(), null).toString();
}
/**
* Identify the Locale this StringManager is associated with
*
* @return The Locale associated with this instance
*/
public Locale getLocale() {
return locale;
}
// --------------------------------------------------------------
// STATIC SUPPORT METHODS
// --------------------------------------------------------------
private static final Map<String,Map<Locale,StringManager>> managers = new HashMap<>();
/**
* The StringManager will be returned for the package in which the class is located. If a manager for that package
* already exists, it will be reused, else a new StringManager will be created and returned.
*
* @param clazz The class for which to retrieve the StringManager
*
* @return The StringManager for the given class.
*/
public static final StringManager getManager(Class<?> clazz) {
return getManager(clazz.getPackage().getName());
}
/**
* If a manager for a package already exists, it will be reused, else a new StringManager will be created and
* returned.
*
* @param packageName The package name
*
* @return The StringManager for the given package.
*/
public static final StringManager getManager(String packageName) {
return getManager(packageName, Locale.getDefault());
}
/**
* If a manager for a package/Locale combination already exists, it will be reused, else a new StringManager will be
* created and returned.
*
* @param packageName The package name
* @param locale The Locale
*
* @return The StringManager for a particular package and Locale
*/
public static final synchronized StringManager getManager(String packageName, Locale locale) {
Map<Locale,StringManager> map = managers.get(packageName);
if (map == null) {
/*
* Don't want the HashMap size to exceed LOCALE_CACHE_SIZE. Expansion occurs when size() exceeds capacity.
* Therefore keep size at or below capacity. removeEldestEntry() executes after insertion therefore the test
* for removal needs to use one less than the maximum desired size. Note this is an LRU cache.
*/
map = new LinkedHashMap<>(LOCALE_CACHE_SIZE, 0.75f, true) {
private static final long serialVersionUID = 1L;
@Override
protected boolean removeEldestEntry(Map.Entry<Locale,StringManager> eldest) {
if (size() > (LOCALE_CACHE_SIZE - 1)) {
return true;
}
return false;
}
};
managers.put(packageName, map);
}
StringManager mgr = map.get(locale);
if (mgr == null) {
mgr = new StringManager(packageName, locale);
map.put(locale, mgr);
}
return mgr;
}
/**
* Retrieve the StringManager for a list of Locales. The first StringManager found will be returned.
*
* @param packageName The package for which the StringManager is required
* @param requestedLocales the list of Locales
*
* @return the found StringManager or the default StringManager
*/
public static StringManager getManager(String packageName, Enumeration<Locale> requestedLocales) {
while (requestedLocales.hasMoreElements()) {
Locale locale = requestedLocales.nextElement();
StringManager result = getManager(packageName, locale);
if (result.getLocale().equals(locale)) {
return result;
}
}
// Return the default
return getManager(packageName);
}
}