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    
015    package org.apache.tapestry.services.impl;
016    
017    import java.util.HashMap;
018    import java.util.Map;
019    
020    import ognl.Ognl;
021    
022    import org.apache.hivemind.ApplicationRuntimeException;
023    import org.apache.tapestry.event.ReportStatusEvent;
024    import org.apache.tapestry.event.ReportStatusListener;
025    import org.apache.tapestry.event.ResetEventListener;
026    import org.apache.tapestry.services.ExpressionCache;
027    
028    /**
029     * @author Howard M. Lewis Ship
030     * @since 4.0
031     */
032    public class ExpressionCacheImpl implements ExpressionCache, ResetEventListener,
033            ReportStatusListener
034    {
035        private String _serviceId;
036    
037        private Map _cache = new HashMap();
038    
039        public synchronized void resetEventDidOccur()
040        {
041            _cache.clear();
042        }
043    
044        public void reportStatus(ReportStatusEvent event)
045        {
046            event.title(_serviceId);
047    
048            event.property("cached expression count", _cache.size());
049            event.collection("cached expressions", _cache.keySet());
050        }
051    
052        public synchronized Object getCompiledExpression(String expression)
053        {
054            Object result = _cache.get(expression);
055    
056            if (result == null)
057            {
058                result = parse(expression);
059                _cache.put(expression, result);
060            }
061    
062            return result;
063        }
064    
065        private Object parse(String expression)
066        {
067            try
068            {
069                return Ognl.parseExpression(expression);
070            }
071            catch (Exception ex)
072            {
073                throw new ApplicationRuntimeException(ImplMessages.unableToParseExpression(
074                        expression,
075                        ex), ex);
076            }
077        }
078    
079        public void setServiceId(String serviceId)
080        {
081            _serviceId = serviceId;
082        }
083    
084    }