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1   /*
2    * Copyright 2006-2008 the original author or authors.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    * 
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package org.springframework.osgi.extender.support;
18  
19  import org.osgi.framework.BundleContext;
20  import org.springframework.beans.factory.InitializingBean;
21  import org.springframework.osgi.context.DelegatedExecutionOsgiBundleApplicationContext;
22  import org.springframework.osgi.extender.OsgiApplicationContextCreator;
23  import org.springframework.util.Assert;
24  
25  /**
26   * Useful {@link OsgiApplicationContextCreator} implementation that dictates
27   * whether the default application context used by the Spring-DM extender should
28   * be created (or not) based on a <code>boolean</code> value. This allows
29   * clients to handle only the bundleContext filtering while being decoupled from
30   * the context creation process:
31   * 
32   * <pre class="code">
33   * 
34   * ConditionalApplicationContextCreator creator = new ConditionalApplicationContextCreator();
35   * 
36   * creator.setFilter(new ConditionalApplicationContextCreator.BundleContextFilter() {
37   * 	// filter bundles with no copyright
38   * 	public boolean matches(BundleContext bundleContext) {
39   * 		return bundleContext.getBundle().getHeaders().get(Constants.BUNDLE_COPYRIGHT) != null)
40   * 	}
41   * }
42   * 
43   * creator.createApplicationContext(bundleContext); 
44   * </pre>
45   * 
46   * @see OsgiApplicationContextCreator
47   * @author Costin Leau
48   */
49  public class ConditionalApplicationContextCreator implements OsgiApplicationContextCreator, InitializingBean {
50  
51  	/**
52  	 * Callback used to filter the bundle contexts for which the default
53  	 * application contexts are created.
54  	 * 
55  	 * @author Costin Leau
56  	 * 
57  	 */
58  	public static interface BundleContextFilter {
59  
60  		/**
61  		 * Determines if the given bundle context matches the filter criteria.
62  		 * 
63  		 * @param bundleContext the OSGi bundle context to check
64  		 * @return true if the bundle context matches, false otherwise.
65  		 */
66  		boolean matches(BundleContext bundleContext);
67  	}
68  
69  
70  	private BundleContextFilter filter;
71  
72  	private OsgiApplicationContextCreator delegatedContextCreator;
73  
74  
75  	public void afterPropertiesSet() throws Exception {
76  		Assert.notNull(filter, "filter property is required");
77  		if (delegatedContextCreator == null)
78  			delegatedContextCreator = new DefaultOsgiApplicationContextCreator();
79  	}
80  
81  	public DelegatedExecutionOsgiBundleApplicationContext createApplicationContext(BundleContext bundleContext)
82  			throws Exception {
83  		if (filter.matches(bundleContext))
84  			return delegatedContextCreator.createApplicationContext(bundleContext);
85  		else
86  			return null;
87  	}
88  
89  	/**
90  	 * Sets the {@link BundleContextFilter} used by this context creator.
91  	 * 
92  	 * @param filter The bundle context filter to set.
93  	 */
94  	public void setFilter(BundleContextFilter filter) {
95  		this.filter = filter;
96  	}
97  
98  	/**
99  	 * Sets the {@link OsgiApplicationContextCreator} used by this context
100 	 * creator for the actual creation. If none is specified,
101 	 * {@link DefaultOsgiApplicationContextCreator} is used.
102 	 * 
103 	 * @param delegatedContextCreator the instance used for creating the
104 	 * application context
105 	 */
106 	public void setDelegatedApplicationContextCreator(OsgiApplicationContextCreator delegatedContextCreator) {
107 		this.delegatedContextCreator = delegatedContextCreator;
108 	}
109 }