001    // Copyright 2006, 2009, 2011 The Apache Software Foundation
002    //
003    // Licensed under the Apache License, Version 2.0 (the "License");
004    // you may not use this file except in compliance with the License.
005    // You may obtain a copy of the License at
006    //
007    //     http://www.apache.org/licenses/LICENSE-2.0
008    //
009    // Unless required by applicable law or agreed to in writing, software
010    // distributed under the License is distributed on an "AS IS" BASIS,
011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012    // See the License for the specific language governing permissions and
013    // limitations under the License.
014    
015    package org.apache.tapestry5.ioc.util;
016    
017    import org.apache.tapestry5.ioc.MessageFormatter;
018    import org.apache.tapestry5.ioc.Messages;
019    import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
020    import org.apache.tapestry5.ioc.internal.util.MessageFormatterImpl;
021    
022    import java.util.Locale;
023    import java.util.Map;
024    
025    /**
026     * Abstract implementation of {@link Messages} that doesn't know where values come from (that information is supplied in
027     * a subclass, via the {@link #valueForKey(String)} method).
028     */
029    public abstract class AbstractMessages implements Messages
030    {
031        /**
032         * String key to MF instance.
033         */
034        private final Map<String, MessageFormatter> cache = CollectionFactory.newConcurrentMap();
035    
036        private final Locale locale;
037    
038        protected AbstractMessages(Locale locale)
039        {
040            this.locale = locale;
041        }
042    
043        /**
044         * Invoked to provide the value for a particular key. This may be invoked multiple times even for the same key. The
045         * implementation should <em>ignore the case of the key</em>.
046         *
047         * @param key the key to obtain a value for (case insensitive)
048         * @return the value for the key, or null if this instance can not provide the value
049         */
050        protected abstract String valueForKey(String key);
051    
052    
053        public boolean contains(String key)
054        {
055            return valueForKey(key) != null;
056        }
057    
058        public String get(String key)
059        {
060            if (contains(key)) return valueForKey(key);
061    
062            return String.format("[[missing key: %s]]", key);
063        }
064    
065        public MessageFormatter getFormatter(String key)
066        {
067            MessageFormatter result = cache.get(key);
068    
069            if (result == null)
070            {
071                result = buildMessageFormatter(key);
072                cache.put(key, result);
073            }
074    
075            return result;
076        }
077    
078        private MessageFormatter buildMessageFormatter(String key)
079        {
080            String format = get(key);
081    
082            return new MessageFormatterImpl(format, locale);
083        }
084    
085        public String format(String key, Object... args)
086        {
087            return getFormatter(key).format(args);
088        }
089    
090    }