IExtensionPoint


1   /*******************************************************************************
2    * Copyright (c) 2000, 2006 IBM Corporation and others.
3    * All rights reserved. This program and the accompanying materials
4    * are made available under the terms of the Eclipse Public License v1.0
5    * which accompanies this distribution, and is available at
6    * http://www.eclipse.org/legal/epl-v10.html
7    * 
8    * Contributors:
9    *     IBM Corporation - initial API and implementation
10   *******************************************************************************/
11  package org.eclipse.core.runtime;
12  
13  /**
14   * An extension point declared in a plug-in.
15   * Except for the list of extensions plugged in to it, the information 
16   * available for an extension point is obtained from the declaring plug-in's 
17   * manifest (<code>plugin.xml</code>) file.
18   * <p>
19   * These registry objects are intended for relatively short-term use. Clients that 
20   * deal with these objects must be aware that they may become invalid if the 
21   * declaring plug-in is updated or uninstalled. If this happens, all methods except
22   * {@link #isValid()} will throw {@link InvalidRegistryObjectException}.
23   * For extension point objects, the most common case is code in a plug-in dealing
24   * with one of the extension points it declares. These extension point objects are
25   * guaranteed to be valid while the plug-in is active. Code in a plug-in that has
26   * declared that it is not dynamic aware (or not declared anything) can also safely
27   * ignore this issue, since the registry would not be modified while it is
28   * active. However, code in a plug-in that declares that it is dynamic aware
29   * must be careful if it access the extension point object of a different plug-in,
30   * because it's at risk if that other plug-in is removed. Similarly,
31   * tools that analyze or display the extension registry are vulnerable.
32   * Client code can pre-test for invalid objects by calling {@link #isValid()},
33   * which never throws this exception. However, pre-tests are usually not sufficient
34   * because of the possibility of the extension point object becoming invalid as a
35   * result of a concurrent activity. At-risk clients must treat 
36   * <code>InvalidRegistryObjectException</code> as if it were a checked exception.
37   * Also, such clients should probably register a listener with the extension registry
38   * so that they receive notification of any changes to the registry.
39   * </p><p>
40   * This interface can be used without OSGi running.
41   * </p><p>
42   * This interface is not intended to be implemented by clients.
43   * </p>
44   */
45  public interface IExtensionPoint {
46      /**
47       * Returns all configuration elements from all extensions configured
48       * into this extension point. Returns an empty array if this extension 
49       * point has no extensions configured, or none of the extensions 
50       * contain configuration elements.
51       *
52       * @return the configuration elements for all extension configured 
53       *   into this extension point
54       * @throws InvalidRegistryObjectException if this extension point is no longer valid
55       */
56      public IConfigurationElement[] getConfigurationElements() throws InvalidRegistryObjectException;
57  
58      /**
59       * Returns the namespace for this extension point. This value can be used
60       * in various global facilities to discover this extension point's provider.
61       * 
62       * @return the namespace for this extension point
63       * @throws InvalidRegistryObjectException if this extension point is no longer valid
64       * @see IExtensionRegistry
65       * @since 3.0
66       * @deprecated As namespace is no longer restricted to the contributor name, 
67       *  use {@link #getNamespaceIdentifier()} to obtain namespace name or {@link #getContributor()}
68       *  to get the name of the contributor of this registry element.  
69       * <p>
70       * In the past namespace was dictated by the name of the bundle. If bundle <code>org.abc</code> 
71       * contributed registry element with Id of <code>MyId</code>, the namespace of 
72       * the element was always set to <code>org.abc</code>, producing the qualified name of 
73       * <code>org.abc.MyId</code>.
74       * </p><p>
75       * The namespace used to be the same as the bundle name. As a result, the {@link #getNamespace()} 
76       * method was used both to obtain the name of the bundle and to obtain the namespace of a registry 
77       * element.
78       * </p><p>
79       * Since 3.2, the extension registry allows elements to specify qualified name. The extension point 
80       * of the plug-in <code>org.abc</code> could specify <code>org.zzz.MyExtPoint</code> as 
81       * an Id. In this case, namespace name is <code>org.zzz</code>, but the contributor 
82       * name is <code>org.abc</code>.  
83       * </p><p>
84       * (The use of a simple Id is still a preferred way. Whenever possible, specify only the simple 
85       * Id and let runtime take care of the rest.)
86       * </p><p>
87       * If your code used the {@link #getNamespace()} to obtain the name of the contributing bundle, 
88       * use {@link #getContributor()}. The typical usage pattern here is to find a bundle name to obtain 
89       * some information from the corresponding OSGi bundle. For example, deducing the file location 
90       * specified as a relative path to the bundle install location would fall into this group.
91       * </p><p>
92       * If your code used the {@link #getNamespace()} to obtain the namespace of the registry element, 
93       * use {@link #getNamespaceIdentifier()}. Typically, this is the case when code is trying to process 
94       * registry elements belonging to some logical group. For example, processing notifications for all 
95       * elements belonging to the <code>org.abc</code> namespace would fall into this category.
96       * </p>
97       */
98      public String   getNamespace() throws InvalidRegistryObjectException;
99  
100     /**
101      * Returns the namespace name for this extension point.
102      * 
103      * @return the namespace name for this extension point
104      * @throws InvalidRegistryObjectException if this extension point is no longer valid
105      * @since org.eclipse.equinox.registry 3.2   
106      */
107     public String   getNamespaceIdentifier() throws InvalidRegistryObjectException;
108 
109     /**
110      * Returns the contributor of this extension point.
111      * 
112      * @return the contributor for this extension point
113      * @throws InvalidRegistryObjectException if this extension point is no longer valid
114      * @since org.eclipse.equinox.registry 3.2   
115      */
116     public IContributor getContributor() throws InvalidRegistryObjectException;
117 
118     /**
119      * Returns the extension with the given unique identifier configured into
120      * this extension point, or <code>null</code> if there is no such extension.
121      * Since an extension might not have an identifier, some extensions
122      * can only be found via the <code>getExtensions</code> method.
123      *
124      * @param extensionId the unique identifier of an extension 
125      *      (e.g. <code>"com.example.acme.main"</code>).
126      * @return an extension, or <code>null</code>
127      * @throws InvalidRegistryObjectException if this extension point is no longer valid
128      */
129     public IExtension getExtension(String   extensionId) throws InvalidRegistryObjectException;
130 
131     /**
132      * Returns all extensions configured into this extension point.
133      * Returns an empty array if this extension point has no extensions.
134      *
135      * @return the extensions configured into this extension point
136      * @throws InvalidRegistryObjectException if this extension point is no longer valid
137      */
138     public IExtension[] getExtensions() throws InvalidRegistryObjectException;
139 
140     /**
141      * Returns a displayable label for this extension point.
142      * Returns the empty string if no label for this extension point
143      * is specified in the plug-in manifest file.
144      * <p> Note that any translation specified in the plug-in manifest
145      * file is automatically applied.
146      * </p>
147      *
148      * @return a displayable string label for this extension point,
149      *    possibly the empty string
150      * @throws InvalidRegistryObjectException if this extension point is no longer valid
151      */
152     public String   getLabel() throws InvalidRegistryObjectException;
153 
154     /**
155      * Returns reference to the extension point schema. The schema 
156      * reference is returned as a URL path relative to the plug-in 
157      * installation URL. 
158      * Returns the empty string if no schema for this extension point
159      * is specified in the plug-in manifest file.
160      *
161      * @return a relative URL path, or an empty string
162      * @throws InvalidRegistryObjectException if this extension point is no longer valid
163      */
164     public String   getSchemaReference() throws InvalidRegistryObjectException;
165 
166     /**
167      * Returns the simple identifier of this extension point.
168      * This identifier is a non-empty string containing no
169      * period characters (<code>'.'</code>) and is guaranteed
170      * to be unique within the namespace.
171      *
172      * @return the simple identifier of the extension point (e.g. <code>"builders"</code>)
173      * @throws InvalidRegistryObjectException if this extension point is no longer valid
174      */
175     public String   getSimpleIdentifier() throws InvalidRegistryObjectException;
176 
177     /**
178      * Returns the unique identifier of this extension point.
179      * This identifier is unique within the plug-in registry, and
180      * is composed of the namespace for this extension point 
181      * and this extension point's simple identifier.
182      * 
183      *
184      * @return the unique identifier of the extension point
185      *    (e.g. <code>"org.eclipse.core.resources.builders"</code>)
186      * @throws InvalidRegistryObjectException if this extension point is no longer valid
187      */
188     public String   getUniqueIdentifier() throws InvalidRegistryObjectException;
189 
190     /* (non-javadoc) 
191      * @see Object#equals(java.lang.Object)
192      */
193     public boolean equals(Object   o);
194 
195     /**
196      * Returns whether this extension point object is valid.
197      * 
198      * @return <code>true</code> if the object is valid, and <code>false</code>
199      * if it is no longer valid
200      * @since 3.1
201      */
202     public boolean isValid();
203 }
204
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