001// Copyright 2006, 2007, 2008, 2010, 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.internal.services;
016
017import java.util.Collections;
018import java.util.List;
019import java.util.Map;
020
021import org.apache.tapestry5.func.F;
022import org.apache.tapestry5.internal.event.InvalidationEventHubImpl;
023import org.apache.tapestry5.internal.util.MultiKey;
024import org.apache.tapestry5.ioc.Messages;
025import org.apache.tapestry5.ioc.Resource;
026import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
027import org.apache.tapestry5.ioc.internal.util.URLChangeTracker;
028import org.apache.tapestry5.services.messages.PropertiesFileParser;
029import org.apache.tapestry5.services.pageload.ComponentResourceLocator;
030import org.apache.tapestry5.services.pageload.ComponentResourceSelector;
031
032/**
033 * A utility class that encapsulates all the logic for reading properties files and assembling {@link Messages} from
034 * them, in accordance with extension rules and locale. This represents code that was refactored out of
035 * {@link ComponentMessagesSourceImpl}. This class can be used as a base class, though the existing code base uses it as
036 * a utility. Composition trumps inheritance!
037 * <p/>
038 * The message catalog for a component is the combination of all appropriate properties files for the component, plus
039 * any keys inherited form base components and, ultimately, the application global message catalog. At some point we
040 * should add support for per-library message catalogs.
041 * <p/>
042 * Message catalogs are read using the UTF-8 character set. This is tricky in JDK 1.5; we read the file into memory then
043 * feed that bytestream to Properties.load().
044 */
045public class MessagesSourceImpl extends InvalidationEventHubImpl implements MessagesSource
046{
047    private final URLChangeTracker tracker;
048
049    private final PropertiesFileParser propertiesFileParser;
050
051    private final ComponentResourceLocator resourceLocator;
052
053    /**
054     * Keyed on bundle id and ComponentResourceSelector.
055     */
056    private final Map<MultiKey, Messages> messagesByBundleIdAndSelector = CollectionFactory.newConcurrentMap();
057
058    /**
059     * Keyed on bundle id and ComponentResourceSelector, the cooked properties include properties inherited from less
060     * locale-specific properties files, or inherited from parent bundles.
061     */
062    private final Map<MultiKey, Map<String, String>> cookedProperties = CollectionFactory.newConcurrentMap();
063
064    /**
065     * Raw properties represent just the properties read from a specific properties file, in isolation.
066     */
067    private final Map<Resource, Map<String, String>> rawProperties = CollectionFactory.newConcurrentMap();
068
069    private final Map<String, String> emptyMap = Collections.emptyMap();
070
071    public MessagesSourceImpl(boolean productionMode, URLChangeTracker tracker,
072            ComponentResourceLocator resourceLocator, PropertiesFileParser propertiesFileParser)
073    {
074        super(productionMode);
075
076        this.tracker = tracker;
077        this.propertiesFileParser = propertiesFileParser;
078        this.resourceLocator = resourceLocator;
079    }
080
081    public void checkForUpdates()
082    {
083        if (tracker != null && tracker.containsChanges())
084        {
085            messagesByBundleIdAndSelector.clear();
086            cookedProperties.clear();
087            rawProperties.clear();
088
089            tracker.clear();
090
091            fireInvalidationEvent();
092        }
093    }
094
095    public Messages getMessages(MessagesBundle bundle, ComponentResourceSelector selector)
096    {
097        MultiKey key = new MultiKey(bundle.getId(), selector);
098
099        Messages result = messagesByBundleIdAndSelector.get(key);
100
101        if (result == null)
102        {
103            result = buildMessages(bundle, selector);
104            messagesByBundleIdAndSelector.put(key, result);
105        }
106
107        return result;
108    }
109
110    private Messages buildMessages(MessagesBundle bundle, ComponentResourceSelector selector)
111    {
112        Map<String, String> properties = findBundleProperties(bundle, selector);
113
114        return new MapMessages(selector.locale, properties);
115    }
116
117    /**
118     * Assembles a set of properties appropriate for the bundle in question, and the desired locale. The properties
119     * reflect the properties of the bundles' parent (if any) for the locale, overalyed with any properties defined for
120     * this bundle and its locale.
121     */
122    private Map<String, String> findBundleProperties(MessagesBundle bundle, ComponentResourceSelector selector)
123    {
124        if (bundle == null)
125            return emptyMap;
126
127        MultiKey key = new MultiKey(bundle.getId(), selector);
128
129        Map<String, String> existing = cookedProperties.get(key);
130
131        if (existing != null)
132            return existing;
133
134        // What would be cool is if we could maintain a cache of bundle id + locale -->
135        // Resource. That would optimize quite a bit of this; may need to use an alternative to
136        // LocalizedNameGenerator.
137
138        Resource propertiesResource = bundle.getBaseResource().withExtension("properties");
139
140        List<Resource> localizations = resourceLocator.locateMessageCatalog(propertiesResource, selector);
141
142        // Localizations are now in least-specific to most-specific order.
143
144        Map<String, String> previous = findBundleProperties(bundle.getParent(), selector);
145
146        for (Resource localization : F.flow(localizations).reverse())
147        {
148            Map<String, String> rawProperties = getRawProperties(localization);
149
150            // Woould be nice to write into the cookedProperties cache here,
151            // but we can't because we don't know the selector part of the MultiKey.
152
153            previous = extend(previous, rawProperties);
154        }
155
156        cookedProperties.put(key, previous);
157
158        return previous;
159    }
160
161    /**
162     * Returns a new map consisting of all the properties in previous overlayed with all the properties in
163     * rawProperties. If rawProperties is empty, returns just the base map.
164     */
165    private Map<String, String> extend(Map<String, String> base, Map<String, String> rawProperties)
166    {
167        if (rawProperties.isEmpty())
168            return base;
169
170        // Make a copy of the base Map
171
172        Map<String, String> result = CollectionFactory.newCaseInsensitiveMap(base);
173
174        // Add or overwrite properties to the copy
175
176        result.putAll(rawProperties);
177
178        return result;
179    }
180
181    private Map<String, String> getRawProperties(Resource localization)
182    {
183        Map<String, String> result = rawProperties.get(localization);
184
185        if (result == null)
186        {
187            result = readProperties(localization);
188
189            rawProperties.put(localization, result);
190        }
191
192        return result;
193    }
194
195    /**
196     * Creates and returns a new map that contains properties read from the properties file.
197     */
198    private Map<String, String> readProperties(Resource resource)
199    {
200        if (!resource.exists())
201            return emptyMap;
202
203        if (tracker != null)
204        {
205            tracker.add(resource.toURL());
206        }
207
208        try
209        {
210            return propertiesFileParser.parsePropertiesFile(resource);
211        }
212        catch (Exception ex)
213        {
214            throw new RuntimeException(ServicesMessages.failureReadingMessages(resource, ex), ex);
215        }
216    }
217
218}