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 org.apache.hivemind.ApplicationRuntimeException; 018import org.apache.hivemind.ServiceImplementationFactory; 019import org.apache.hivemind.ServiceImplementationFactoryParameters; 020import org.apache.hivemind.lib.DefaultImplementationBuilder; 021import org.apache.tapestry.spec.IApplicationSpecification; 022 023/** 024 * An implementation of {@link org.apache.hivemind.ServiceImplementationFactory}that looks for a 025 * service implementation provided as an 026 * {@link org.apache.tapestry.spec.ILibrarySpecification#getExtension(String) application 027 * extension}. If no such extension exists, then a 028 * {@link org.apache.hivemind.lib.DefaultImplementationBuilder default implementation}is 029 * constructed and returned instead. This allows compatibility with Tapestry 3.0 and earlier 030 * application extensions (though those will be phased out in the future). 031 * 032 * @author Howard Lewis Ship 033 * @since 4.0 034 */ 035public class ExtensionLookupFactory implements ServiceImplementationFactory 036{ 037 private IApplicationSpecification _specification; 038 039 private DefaultImplementationBuilder _defaultBuilder; 040 041 public Object createCoreServiceImplementation( 042 ServiceImplementationFactoryParameters factorParameters) 043 { 044 ExtensionLookupParameter p = (ExtensionLookupParameter) factorParameters.getParameters() 045 .get(0); 046 047 String extensionName = p.getExtensionName(); 048 049 Class serviceInterface = factorParameters.getServiceInterface(); 050 051 try 052 { 053 if (_specification.checkExtension(extensionName)) 054 return _specification.getExtension(extensionName, serviceInterface); 055 056 if (p.getDefault() != null) 057 return p.getDefault(); 058 059 return _defaultBuilder.buildDefaultImplementation(serviceInterface); 060 } 061 catch (Exception ex) 062 { 063 throw new ApplicationRuntimeException(ex.getMessage(), p.getLocation(), ex); 064 } 065 } 066 067 public void setDefaultBuilder(DefaultImplementationBuilder builder) 068 { 069 _defaultBuilder = builder; 070 } 071 072 public void setSpecification(IApplicationSpecification specification) 073 { 074 _specification = specification; 075 } 076 077}