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
015package org.apache.tapestry5.commons.util;
016
017import java.util.Locale;
018import java.util.Map;
019
020import org.apache.tapestry5.commons.MessageFormatter;
021import org.apache.tapestry5.commons.Messages;
022import org.apache.tapestry5.commons.internal.util.MessageFormatterImpl;
023
024/**
025 * Abstract implementation of {@link Messages} that doesn't know where values come from (that information is supplied in
026 * a subclass, via the {@link #valueForKey(String)} method).
027 */
028public abstract class AbstractMessages implements Messages
029{
030    /**
031     * String key to MF instance.
032     */
033    private final Map<String, MessageFormatter> cache = CollectionFactory.newConcurrentMap();
034
035    private final Locale locale;
036
037    protected AbstractMessages(Locale locale)
038    {
039        this.locale = locale;
040    }
041
042    /**
043     * Invoked to provide the value for a particular key. This may be invoked multiple times even for the same key. The
044     * implementation should <em>ignore the case of the key</em>.
045     *
046     * @param key the key to obtain a value for (case insensitive)
047     * @return the value for the key, or null if this instance can not provide the value
048     */
049    protected abstract String valueForKey(String key);
050
051
052    @Override
053    public boolean contains(String key)
054    {
055        return valueForKey(key) != null;
056    }
057
058    @Override
059    public String get(String key)
060    {
061        if (contains(key)) return valueForKey(key);
062
063        return String.format("[[missing key: %s]]", key);
064    }
065
066    @Override
067    public MessageFormatter getFormatter(String key)
068    {
069        MessageFormatter result = cache.get(key);
070
071        if (result == null)
072        {
073            result = buildMessageFormatter(key);
074            cache.put(key, result);
075        }
076
077        return result;
078    }
079
080    private MessageFormatter buildMessageFormatter(String key)
081    {
082        String format = get(key);
083
084        return new MessageFormatterImpl(format, locale);
085    }
086
087    @Override
088    public String format(String key, Object... args)
089    {
090        return getFormatter(key).format(args);
091    }
092
093}