tapestry/tapestry-framework/src/java/org/apache/tapestry/services/impl/InfrastructureObjectProvider.java

// Copyright 2004, 2005 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package org.apache.tapestry.services.impl;

import java.util.HashMap;
import java.util.Map;

import org.apache.hivemind.ErrorLog;
import org.apache.hivemind.Location;
import org.apache.hivemind.internal.Module;
import org.apache.hivemind.service.ObjectProvider;
import org.apache.hivemind.util.PropertyUtils;
import org.apache.tapestry.services.Infrastructure;

/**
 * An ObjectProvider that streamlines access to the central
 * {@link org.apache.tapestry.services.Infrastructure}object. The locator for this provider is the
 * name of a property of the Infrastructure.
 * 
 * @author Howard Lewis Ship
 * @since 4.0
 */

public class InfrastructureObjectProvider implements ObjectProvider
{
    private ErrorLog _errorLog;

    private Infrastructure _infrastructure;

    private Map _cache = new HashMap();

    public synchronized Object provideObject(Module contributingModule, Class propertyType,
            String locator, Location location)
    {
        Object result = _cache.get(locator);

        if (result == null)
        {
            result = readProperty(locator, location);
            _cache.put(locator, result);
        }

        return result;
    }

    Object readProperty(String locator, Location location)
    {
        try
        {            
            if (PropertyUtils.isReadable(_infrastructure, locator))
                return PropertyUtils.read(_infrastructure, locator);

            return _infrastructure.getProperty(locator);
        }
        catch (Throwable ex)
        {
            _errorLog.error(ImplMessages.unableToReadInfrastructureProperty(
                    locator,
                    _infrastructure,
                    ex), location, ex);

            return null;
        }
    }

    public void setErrorLog(ErrorLog errorLog)
    {
        _errorLog = errorLog;
    }

    public void setInfrastructure(Infrastructure infrastructure)
    {
        _infrastructure = infrastructure;
    }

}