001    // Copyright 2005 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.tapestry.enhance;
016    
017    import java.lang.reflect.Modifier;
018    
019    import org.apache.hivemind.ErrorLog;
020    import org.apache.hivemind.Location;
021    import org.apache.hivemind.Messages;
022    import org.apache.hivemind.service.BodyBuilder;
023    import org.apache.hivemind.service.MethodSignature;
024    import org.apache.hivemind.util.Defense;
025    import org.apache.tapestry.services.ComponentMessagesSource;
026    import org.apache.tapestry.spec.IComponentSpecification;
027    
028    /**
029     * Injects the read-only {@link org.apache.tapestry.IComponent#getMessages() messages}property into
030     * all components.
031     * 
032     * @author Howard M. Lewis Ship
033     * @since 4.0
034     */
035    public class InjectMessagesWorker implements EnhancementWorker
036    {
037        final String _messagesProperty = "messages";
038    
039        final MethodSignature _methodSignature = new MethodSignature(Messages.class, "getMessages",
040                null, null);
041    
042        private ErrorLog _errorLog;
043    
044        private ComponentMessagesSource _componentMessagesSource;
045        
046        public void performEnhancement(EnhancementOperation op, IComponentSpecification spec)
047        {
048            Location location = spec.getLocation();
049    
050            try
051            {
052                injectMessages(op, location);
053            }
054            catch (Exception ex)
055            {
056                _errorLog.error(EnhanceMessages.errorAddingProperty(_messagesProperty, op
057                        .getBaseClass(), ex), location, ex);
058            }
059        }
060    
061        public void injectMessages(EnhancementOperation op, Location location)
062        {
063            Defense.notNull(op, "op");
064    
065            op.claimReadonlyProperty(_messagesProperty);
066    
067            String sourceField = op.addInjectedField(
068                    "_$componentMessagesSource",
069                    ComponentMessagesSource.class,
070                    _componentMessagesSource);
071    
072            op.addField("_$messages", Messages.class);
073    
074            BodyBuilder builder = new BodyBuilder();
075            builder.begin();
076            builder.addln("if (_$messages == null)");
077            builder.addln("  _$messages = {0}.getMessages(this);", sourceField);
078            builder.addln("return _$messages;");
079            builder.end();
080    
081            op.addMethod(Modifier.PUBLIC, _methodSignature, builder.toString(), location);
082        }
083    
084        public void setComponentMessagesSource(ComponentMessagesSource componentMessagesSource)
085        {
086            _componentMessagesSource = componentMessagesSource;
087        }
088    
089        public void setErrorLog(ErrorLog errorLog)
090        {
091            _errorLog = errorLog;
092        }
093    }