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.Locale;
018
019import org.apache.hivemind.ApplicationRuntimeException;
020import org.apache.hivemind.ClassResolver;
021import org.apache.hivemind.ErrorLog;
022import org.apache.tapestry.IEngine;
023import org.apache.tapestry.engine.BaseEngine;
024import org.apache.tapestry.services.EngineFactory;
025import org.apache.tapestry.spec.IApplicationSpecification;
026
027/**
028 * Standard implementation of {@link org.apache.tapestry.services.EngineFactory} service. This
029 * should do for most purposes, since a major focus of Tapestry 4.0 is to no longer require
030 * subclassing of {@link org.apache.tapestry.engine.BaseEngine}.
031 * 
032 * @author Howard Lewis Ship
033 * @since 4.0
034 */
035public class EngineFactoryImpl implements EngineFactory
036{
037    private IApplicationSpecification _applicationSpecification;
038
039    private String _defaultEngineClassName;
040
041    private EngineConstructor _constructor;
042
043    private ClassResolver _classResolver;
044
045    private ErrorLog _errorLog;
046
047    interface EngineConstructor
048    {
049        IEngine construct();
050    }
051
052    // TODO: Create a BaseEngineConstructor that is hardcoded to
053    // instantiate a BaseEngine instance, without using reflection
054    // (for efficiency).
055
056    static class ReflectiveEngineConstructor implements EngineConstructor
057    {
058        private Class _engineClass;
059
060        ReflectiveEngineConstructor(Class engineClass)
061        {
062            _engineClass = engineClass;
063        }
064
065        public IEngine construct()
066        {
067            try
068            {
069                return (IEngine) _engineClass.newInstance();
070            }
071            catch (Exception ex)
072            {
073                throw new ApplicationRuntimeException(ImplMessages.errorInstantiatingEngine(
074                        _engineClass,
075                        ex), ex);
076            }
077        }
078    }
079
080    public void initializeService()
081    {
082        String engineClassName = _applicationSpecification.getEngineClassName();
083
084        // TODO: Check in web.xml first.
085
086        if (engineClassName == null)
087            engineClassName = _defaultEngineClassName;
088
089        Class engineClass = _classResolver.checkForClass(engineClassName);
090
091        if (engineClass == null)
092        {
093            _errorLog.error(ImplMessages.engineClassNotFound(engineClassName), null, null);
094            engineClass = BaseEngine.class;
095        }
096
097        _constructor = new ReflectiveEngineConstructor(engineClass);
098    }
099
100    public IEngine constructNewEngineInstance(Locale locale)
101    {
102        IEngine result = _constructor.construct();
103
104        result.setLocale(locale);
105
106        return result;
107    }
108
109    public void setApplicationSpecification(IApplicationSpecification specification)
110    {
111        _applicationSpecification = specification;
112    }
113
114    public void setClassResolver(ClassResolver resolver)
115    {
116        _classResolver = resolver;
117    }
118
119    public void setDefaultEngineClassName(String string)
120    {
121        _defaultEngineClassName = string;
122    }
123
124    public void setErrorLog(ErrorLog errorLog)
125    {
126        _errorLog = errorLog;
127    }
128
129}