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Java > Open Source Codes > org > apache > tapestry > services > impl > ExtensionLookupFactory


1 // Copyright 2004, 2005 The Apache Software Foundation
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 package org.apache.tapestry.services.impl;
16
17 import org.apache.hivemind.ApplicationRuntimeException;
18 import org.apache.hivemind.ServiceImplementationFactory;
19 import org.apache.hivemind.ServiceImplementationFactoryParameters;
20 import org.apache.hivemind.lib.DefaultImplementationBuilder;
21 import org.apache.tapestry.spec.IApplicationSpecification;
22
23 /**
24  * An implementation of {@link org.apache.hivemind.ServiceImplementationFactory}that looks for a
25  * service implementation provided as an
26  * {@link org.apache.tapestry.spec.ILibrarySpecification#getExtension(String) application
27  * extension}. If no such extension exists, then a
28  * {@link org.apache.hivemind.lib.DefaultImplementationBuilder default implementation}is
29  * constructed and returned instead. This allows compatibility with Tapestry 3.0 and earlier
30  * application extensions (though those will be phased out in the future).
31  *
32  * @author Howard Lewis Ship
33  * @since 4.0
34  */
35 public class ExtensionLookupFactory implements ServiceImplementationFactory
36 {
37     private IApplicationSpecification _specification;
38
39     private DefaultImplementationBuilder _defaultBuilder;
40
41     public Object JavaDoc createCoreServiceImplementation(
42             ServiceImplementationFactoryParameters factorParameters)
43     {
44         ExtensionLookupParameter p = (ExtensionLookupParameter) factorParameters.getParameters()
45                 .get(0);
46
47         String JavaDoc extensionName = p.getExtensionName();
48
49         Class JavaDoc serviceInterface = factorParameters.getServiceInterface();
50
51         try
52         {
53             if (_specification.checkExtension(extensionName))
54                 return _specification.getExtension(extensionName, serviceInterface);
55
56             if (p.getDefault() != null)
57                 return p.getDefault();
58
59             return _defaultBuilder.buildDefaultImplementation(serviceInterface);
60         }
61         catch (Exception JavaDoc ex)
62         {
63             throw new ApplicationRuntimeException(ex.getMessage(), p.getLocation(), ex);
64         }
65     }
66
67     public void setDefaultBuilder(DefaultImplementationBuilder builder)
68     {
69         _defaultBuilder = builder;
70     }
71
72     public void setSpecification(IApplicationSpecification specification)
73     {
74         _specification = specification;
75     }
76
77 }
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