    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}