ComponentContext


1   /*
2    * $Header: /cvshome/build/org.osgi.service.component/src/org/osgi/service/component/ComponentContext.java,v 1.20 2006/06/16 16:31:26 hargrave Exp $
3    *
4    * Copyright (c) OSGi Alliance (2004, 2006). All Rights Reserved.
5    * 
6    * Licensed under the Apache License, Version 2.0 (the "License");
7    * you may not use this file except in compliance with the License.
8    * You may obtain a copy of the License at
9    *
10   *      http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.osgi.service.component;
20  
21  import java.util.Dictionary  ;
22  
23  import org.osgi.framework.*;
24  
25  /**
26   * A Component Context object is used by a component instance to interact with
27   * its execution context including locating services by reference name. Each
28   * component instance has a unique Component Context.
29   * 
30   * <p>
31   * A component's implementation class may optionaly implement an activate
32   * method:
33   * 
34   * <pre>
35   * protected void activate(ComponentContext context);
36   * </pre>
37   * 
38   * If a component implements this method, this method will be called when a
39   * component configuration is activated to provide the component instance's
40   * Component Context object.
41   * 
42   * <p>
43   * A component's implementation class may optionaly implement a deactivate
44   * method:
45   * 
46   * <pre>
47   * protected void deactivate(ComponentContext context);
48   * </pre>
49   * 
50   * If a component implements this method, this method will be called when the
51   * component configuration is deactivated.
52   * 
53   * <p>
54   * The activate and deactivate methods will be called using reflection and must
55   * be protected or public accessible. These methods should not be public methods
56   * so that they do not appear as public methods on the component instance when
57   * used as a service object. These methods will be located by looking through
58   * the component's implementation class hierarchy for the first declaration of
59   * the method. If the method is found, if it is declared protected or public,
60   * the method will be called. Otherwise, the method will not be called.
61   * 
62   * @version $Revision: 1.20 $
63   */
64  public interface ComponentContext {
65      /**
66       * Returns the component properties for this Component Context.
67       * 
68       * @return The properties for this Component Context. The Dictionary is read
69       *         only and cannot be modified.
70       */
71      public Dictionary   getProperties();
72  
73      /**
74       * Returns the service object for the specified reference name.
75       * 
76       * <p>
77       * If the cardinality of the reference is <code>0..n</code> or
78       * <code>1..n</code> and multiple services are bound to the reference, the
79       * service with the highest ranking (as specified in its
80       * <code>Constants.SERVICE_RANKING</code> property) is returned. If there
81       * is a tie in ranking, the service with the lowest service ID (as specified
82       * in its <code>Constants.SERVICE_ID</code> property); that is, the
83       * service that was registered first is returned.
84       * 
85       * @param name The name of a reference as specified in a
86       *        <code>reference</code> element in this component's description.
87       * @return A service object for the referenced service or <code>null</code>
88       *         if the reference cardinality is <code>0..1</code> or
89       *         <code>0..n</code> and no bound service is available.
90       * @throws ComponentException If the Service Component Runtime catches an
91       *         exception while activating the bound service.
92       */
93      public Object   locateService(String   name);
94  
95      /**
96       * Returns the service object for the specified reference name and
97       * <code>ServiceReference</code>.
98       * 
99       * @param name The name of a reference as specified in a
100      *        <code>reference</code> element in this component's description.
101      * @param reference The <code>ServiceReference</code> to a bound service.
102      *        This must be a <code>ServiceReference</code> provided to the
103      *        component via the bind or unbind method for the specified
104      *        reference name.
105      * @return A service object for the referenced service or <code>null</code>
106      *         if the specified <code>ServiceReference</code> is not a bound
107      *         service for the specified reference name.
108      * @throws ComponentException If the Service Component Runtime catches an
109      *         exception while activating the bound service.
110      */
111     public Object   locateService(String   name, ServiceReference reference);
112 
113     /**
114      * Returns the service objects for the specified reference name.
115      * 
116      * @param name The name of a reference as specified in a
117      *        <code>reference</code> element in this component's description.
118      * @return An array of service objects for the referenced service or
119      *         <code>null</code> if the reference cardinality is
120      *         <code>0..1</code> or <code>0..n</code> and no bound service
121      *         is available.
122      * @throws ComponentException If the Service Component Runtime catches an
123      *         exception while activating a bound service.
124      */
125     public Object  [] locateServices(String   name);
126 
127     /**
128      * Returns the <code>BundleContext</code> of the bundle which contains
129      * this component.
130      * 
131      * @return The <code>BundleContext</code> of the bundle containing this
132      *         component.
133      */
134     public BundleContext getBundleContext();
135 
136     /**
137      * If the component instance is registered as a service using the
138      * <code>servicefactory=&quot;true&quot;</code> attribute, then this
139      * method returns the bundle using the service provided by the component
140      * instance.
141      * <p>
142      * This method will return <code>null</code> if:
143      * <ul>
144      * <li>The component instance is not a service, then no bundle can be using
145      * it as a service.
146      * <li>The component instance is a service but did not specify the
147      * <code>servicefactory=&quot;true&quot;</code> attribute, then all
148      * bundles using the service provided by the component instance will share
149      * the same component instance.
150      * <li>The service provided by the component instance is not currently
151      * being used by any bundle.
152      * </ul>
153      * 
154      * @return The bundle using the component instance as a service or
155      *         <code>null</code>.
156      */
157     public Bundle getUsingBundle();
158 
159     /**
160      * Returns the Component Instance object for the component instance
161      * associated with this Component Context.
162      * 
163      * @return The Component Instance object for the component instance.
164      */
165     public ComponentInstance getComponentInstance();
166 
167     /**
168      * Enables the specified component name. The specified component name must
169      * be in the same bundle as this component.
170      * 
171      * @param name The name of a component or <code>null</code> to indicate
172      *        all components in the bundle.
173      */
174     public void enableComponent(String   name);
175 
176     /**
177      * Disables the specified component name. The specified component name must
178      * be in the same bundle as this component.
179      * 
180      * @param name The name of a component.
181      */
182     public void disableComponent(String   name);
183 
184     /**
185      * If the component instance is registered as a service using the
186      * <code>service</code> element, then this method returns the service
187      * reference of the service provided by this component instance.
188      * <p>
189      * This method will return <code>null</code> if the component instance is
190      * not registered as a service.
191      * 
192      * @return The <code>ServiceReference</code> object for the component
193      *         instance or <code>null</code> if the component instance is not
194      *         registered as a service.
195      */
196     public ServiceReference getServiceReference();
197 
198 }
199
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