bundles/org.apache.tomcat/src/org/apache/catalina/tribes/util/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.Hashtable;
import java.util.Locale;
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 formating 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.
 *
 * @version $Id: StringManager.java,v 1.1 2011/06/28 21:14:16 rherrmann Exp $
 *
 * @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 {

    /**
     * The ResourceBundle for this StringManager.
     */
    private ResourceBundle bundle;
    private 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) {
        String bundleName = packageName + ".LocalStrings";
        try {
            bundle = ResourceBundle.getBundle(bundleName, Locale.getDefault());
        } 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 {
                    bundle = ResourceBundle.getBundle(
                            bundleName, Locale.getDefault(), cl);
                } catch(MissingResourceException ex2) {
                    // Ignore
                }
            }
        }
        // Get the actual locale, which may be different from the requested one
        if (bundle != null) {
            locale = bundle.getLocale();
        }
    }

    /**
        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 {
            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
     * @param args
     */
    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();
    }

    // --------------------------------------------------------------
    // STATIC SUPPORT METHODS
    // --------------------------------------------------------------

    private static Hashtable<String, StringManager> managers =
        new Hashtable<String, StringManager>();

    /**
     * Get the StringManager for a particular package. 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
     */
    public static final synchronized StringManager getManager(String packageName) {
        StringManager mgr = managers.get(packageName);
        if (mgr == null) {
            mgr = new StringManager(packageName);
            managers.put(packageName, mgr);
        }
        return mgr;
    }

}