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
015package org.apache.tapestry.enhance;
016
017import java.lang.reflect.Modifier;
018
019import org.apache.hivemind.ErrorLog;
020import org.apache.hivemind.Location;
021import org.apache.hivemind.Messages;
022import org.apache.hivemind.service.BodyBuilder;
023import org.apache.hivemind.service.MethodSignature;
024import org.apache.hivemind.util.Defense;
025import org.apache.tapestry.services.ComponentMessagesSource;
026import 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 */
035public class InjectMessagesWorker implements EnhancementWorker
036{
037    final String MESSAGES_PROPERTY = "messages";
038
039    private ErrorLog _errorLog;
040
041    private ComponentMessagesSource _componentMessagesSource;
042
043    final MethodSignature METHOD_SIGNATURE = new MethodSignature(Messages.class, "getMessages",
044            null, null);
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(MESSAGES_PROPERTY, 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(MESSAGES_PROPERTY);
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, METHOD_SIGNATURE, 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}