001// Copyright 2004, 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.services.impl;
016
017import java.util.HashMap;
018import java.util.Map;
019
020import org.apache.hivemind.ErrorLog;
021import org.apache.hivemind.Location;
022import org.apache.hivemind.internal.Module;
023import org.apache.hivemind.service.ObjectProvider;
024import org.apache.hivemind.util.PropertyUtils;
025import org.apache.tapestry.services.Infrastructure;
026
027/**
028 * An ObjectProvider that streamlines access to the central
029 * {@link org.apache.tapestry.services.Infrastructure}object. The locator for this provider is the
030 * name of a property of the Infrastructure.
031 * 
032 * @author Howard Lewis Ship
033 * @since 4.0
034 */
035
036public class InfrastructureObjectProvider implements ObjectProvider
037{
038    private ErrorLog _errorLog;
039
040    private Infrastructure _infrastructure;
041
042    private Map _cache = new HashMap();
043
044    public synchronized Object provideObject(Module contributingModule, Class propertyType,
045            String locator, Location location)
046    {
047        Object result = _cache.get(locator);
048
049        if (result == null)
050        {
051            result = readProperty(locator, location);
052            _cache.put(locator, result);
053        }
054
055        return result;
056    }
057
058    Object readProperty(String locator, Location location)
059    {
060        try
061        {            
062            if (PropertyUtils.isReadable(_infrastructure, locator))
063                return PropertyUtils.read(_infrastructure, locator);
064
065            return _infrastructure.getProperty(locator);
066        }
067        catch (Throwable ex)
068        {
069            _errorLog.error(ImplMessages.unableToReadInfrastructureProperty(
070                    locator,
071                    _infrastructure,
072                    ex), location, ex);
073
074            return null;
075        }
076    }
077
078    public void setErrorLog(ErrorLog errorLog)
079    {
080        _errorLog = errorLog;
081    }
082
083    public void setInfrastructure(Infrastructure infrastructure)
084    {
085        _infrastructure = infrastructure;
086    }
087
088}