1 /*
2 * Licensed to The Apereo Foundation under one or more contributor license
3 * agreements. See the NOTICE file distributed with this work for additional
4 * information regarding copyright ownership.
5 *
6 *
7 * The Apereo Foundation licenses this file to you under the Educational
8 * Community License, Version 2.0 (the "License"); you may not use this file
9 * except in compliance with the License. You may obtain a copy of the License
10 * at:
11 *
12 * http://opensource.org/licenses/ecl2.txt
13 *
14 * Unless required by applicable law or agreed to in writing, software
15 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
16 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
17 * License for the specific language governing permissions and limitations under
18 * the License.
19 *
20 */
21
22
23 package org.opencastproject.mediapackage;
24
25 import org.opencastproject.util.ConfigurationException;
26
27 /**
28 * Factory to retreive instances of a media package element builder. Use the static method {@link #newInstance()} to
29 * obtain a reference to a concrete implementation of a <code>MediaPackageElementBuilderFactory</code>. This instance
30 * can then be used to create or load media package elements.
31 * <p>
32 * The factory can be configured by specifying the concrete implementation class through the system property
33 * <code>org.opencastproject.mediapackage.elementbuilder</code>.
34 * </p>
35 */
36 public final class MediaPackageElementBuilderFactory {
37
38 /** The implementation class name */
39 private static String builderClassName = "org.opencastproject.mediapackage.MediaPackageElementBuilderImpl";
40
41 /** The singleton instance of this factory */
42 private static final MediaPackageElementBuilderFactory factory = new MediaPackageElementBuilderFactory();
43
44 /** The default builder implementation */
45 private MediaPackageElementBuilder builder = null;
46
47 /**
48 * Returns an instance of a MediaPackageElementBuilderFactory.
49 *
50 * @return the media package element builder factory
51 * @throws ConfigurationException
52 * if the factory cannot be instantiated
53 */
54 public static MediaPackageElementBuilderFactory newInstance() throws ConfigurationException {
55 return factory;
56 }
57
58 /**
59 * Factory method that returns an instance of a media package element builder.
60 * <p>
61 * It uses the following ordered lookup procedure to determine which implementation of the
62 * {@link MediaPackageElementBuilder} interface to use:
63 * <ul>
64 * <li>Implementation specified using the <code>org.opencastproject.mediapackage.elementbuilder</code> system property
65 * </li>
66 * <li>Platform default implementation</li>
67 * </ul>
68 *
69 * @return the media package element builder
70 * @throws ConfigurationException
71 * If the builder cannot be instantiated
72 */
73 public MediaPackageElementBuilder newElementBuilder() throws ConfigurationException {
74 if (builder == null) {
75 try {
76 Class<?> builderClass = Class.forName(builderClassName, true,
77 MediaPackageElementBuilderFactory.class.getClassLoader());
78 builder = (MediaPackageElementBuilder) builderClass.newInstance();
79 } catch (ClassNotFoundException e) {
80 throw new ConfigurationException("Class not found while creating element builder: " + e.getMessage(), e);
81 } catch (InstantiationException e) {
82 throw new ConfigurationException("Instantiation exception while creating element builder: " + e.getMessage(), e);
83 } catch (IllegalAccessException e) {
84 throw new ConfigurationException("Access exception while creating element builder: " + e.getMessage(), e);
85 } catch (Exception e) {
86 throw new ConfigurationException("Exception while creating element builder: " + e.getMessage(), e);
87 }
88 }
89 return builder;
90 }
91
92 }