Copyright (c) 2000, 2009 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2000, 2009 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.runtime;

An extension declared in a plug-in.
All information is obtained from the declaring plug-in's
manifest (plugin.xml) file.
 These registry objects are intended for relatively short-term use. Clients that deal with these objects must be aware that they may become invalid if the declaring plug-in is updated or uninstalled. If this happens, all methods except isValid() will throw InvalidRegistryObjectException. For extension objects, the most common case is code in a plug-in dealing with extensions contributed to one of the extension points it declares. Code in a plug-in that has declared that it is not dynamic aware (or not declared anything) can safely ignore this issue, since the registry would not be modified while it is active. However, code in a plug-in that declares that it is dynamic aware must be careful when accessing the extension objects because they become invalid if the contributing plug-in is removed. Similarly, tools that analyze or display the extension registry are vulnerable. Client code can pre-test for invalid objects by calling isValid(), which never throws this exception. However, pre-tests are usually not sufficient because of the possibility of the extension object becoming invalid as a result of a concurrent activity. At-risk clients must treat InvalidRegistryObjectException as if it were a checked exception.
Also, such clients should probably register a listener with the extension registry
so that they receive notification of any changes to the registry.

This interface can be used without OSGi running.

This interface is not intended to be implemented by clients.

@noimplement
This interface is not intended to be implemented by clients./**
 * An extension declared in a plug-in.
 * All information is obtained from the declaring plug-in's
 * manifest (<code>plugin.xml</code>) file.
 * <p>
 * These registry objects are intended for relatively short-term use. Clients that
 * deal with these objects must be aware that they may become invalid if the
 * declaring plug-in is updated or uninstalled. If this happens, all methods except
 * {@link #isValid()} will throw {@link InvalidRegistryObjectException}.
 * For extension objects, the most common case is code in a plug-in dealing
 * with extensions contributed to one of the extension points it declares.
 * Code in a plug-in that has declared that it is not dynamic aware (or not
 * declared anything) can safely ignore this issue, since the registry
 * would not be modified while it is active. However, code in a plug-in that
 * declares that it is dynamic aware must be careful when accessing the extension
 * objects because they become invalid if the contributing plug-in is removed.
 * Similarly, tools that analyze or display the extension registry are vulnerable.
 * Client code can pre-test for invalid objects by calling {@link #isValid()},
 * which never throws this exception. However, pre-tests are usually not sufficient
 * because of the possibility of the extension object becoming invalid as a
 * result of a concurrent activity. At-risk clients must treat
 * <code>InvalidRegistryObjectException</code> as if it were a checked exception.
 * Also, such clients should probably register a listener with the extension registry
 * so that they receive notification of any changes to the registry.
 * </p><p>
 * This interface can be used without OSGi running.
 * </p><p>
 * This interface is not intended to be implemented by clients.
 * </p>
 * @noimplement This interface is not intended to be implemented by clients.
 */
public interface IExtension {
	
Returns all configuration elements declared by this extension.
These elements are a direct reflection of the configuration
markup supplied in the manifest (plugin.xml)
file for the plug-in that declares this extension.
Returns an empty array if this extension does not declare any
configuration elements.
Throws:
InvalidRegistryObjectException – if this extension is no longer valid
Returns:
the configuration elements declared by this extension/**
	 * Returns all configuration elements declared by this extension.
	 * These elements are a direct reflection of the configuration
	 * markup supplied in the manifest (<code>plugin.xml</code>)
	 * file for the plug-in that declares this extension.
	 * Returns an empty array if this extension does not declare any
	 * configuration elements.
	 *
	 * @return the configuration elements declared by this extension
	 * @throws InvalidRegistryObjectException if this extension is no longer valid
	 */
	public IConfigurationElement[] getConfigurationElements() throws InvalidRegistryObjectException;

	
Returns the namespace for this extension. This value can be used
in various global facilities to discover this extension's provider.
Throws:
InvalidRegistryObjectException – if this extension is no longer valid
See Also:
IExtensionRegistry
Returns:
the namespace for this extension
Since:
3.0
Deprecated:
As namespace is no longer restricted to the contributor name, use getNamespaceIdentifier() to obtain namespace name or getContributor() to get the name of the contributor of this registry element. 

In the past namespace was dictated by the name of the bundle. If bundle org.abc
contributed registry element with Id of MyId, the namespace of
the element was always set to org.abc, producing the qualified name of
org.abc.MyId.
 The namespace used to be the same as the bundle name. As a result, the getNamespace() method was used both to obtain the name of the bundle and to obtain the namespace of a registry element. 

Since 3.2, the extension registry allows elements to specify qualified name. The extension point
of the plug-in org.abc could specify org.zzz.MyExtPoint as
an Id. In this case, namespace name is org.zzz, but the contributor
name is org.abc.

(The use of a simple Id is still a preferred way. Whenever possible, specify only the simple
Id and let runtime take care of the rest.)
 If your code used the getNamespace() to obtain the name of the contributing bundle, use getContributor(). The typical usage pattern here is to find a bundle name to obtain some information from the corresponding OSGi bundle. For example, deducing the file location specified as a relative path to the bundle install location would fall into this group. 
 If your code used the getNamespace() to obtain the namespace of the registry element, use getNamespaceIdentifier(). Typically, this is the case when code is trying to process registry elements belonging to some logical group. For example, processing notifications for all elements belonging to the org.abc namespace would fall into this category.
/**
	 * Returns the namespace for this extension. This value can be used
	 * in various global facilities to discover this extension's provider.
	 *
	 * @return the namespace for this extension
	 * @throws InvalidRegistryObjectException if this extension is no longer valid
	 * @see IExtensionRegistry
	 * @since 3.0
	 * @deprecated As namespace is no longer restricted to the contributor name,
	 * 	use {@link #getNamespaceIdentifier()} to obtain namespace name or {@link #getContributor()}
	 * 	to get the name of the contributor of this registry element.
	 * <p>
	 * In the past namespace was dictated by the name of the bundle. If bundle <code>org.abc</code>
	 * contributed registry element with Id of <code>MyId</code>, the namespace of
	 * the element was always set to <code>org.abc</code>, producing the qualified name of
	 * <code>org.abc.MyId</code>.
	 * </p><p>
	 * The namespace used to be the same as the bundle name. As a result, the {@link #getNamespace()}
	 * method was used both to obtain the name of the bundle and to obtain the namespace of a registry
	 * element.
	 * </p><p>
	 * Since 3.2, the extension registry allows elements to specify qualified name. The extension point
	 * of the plug-in <code>org.abc</code> could specify <code>org.zzz.MyExtPoint</code> as
	 * an Id. In this case, namespace name is <code>org.zzz</code>, but the contributor
	 * name is <code>org.abc</code>.
	 * </p><p>
	 * (The use of a simple Id is still a preferred way. Whenever possible, specify only the simple
	 * Id and let runtime take care of the rest.)
	 * </p><p>
	 * If your code used the {@link #getNamespace()} to obtain the name of the contributing bundle,
	 * use {@link #getContributor()}. The typical usage pattern here is to find a bundle name to obtain
	 * some information from the corresponding OSGi bundle. For example, deducing the file location
	 * specified as a relative path to the bundle install location would fall into this group.
	 * </p><p>
	 * If your code used the {@link #getNamespace()} to obtain the namespace of the registry element,
	 * use {@link #getNamespaceIdentifier()}. Typically, this is the case when code is trying to process
	 * registry elements belonging to some logical group. For example, processing notifications for all
	 * elements belonging to the <code>org.abc</code> namespace would fall into this category.
	 * </p>
	 */
	@Deprecated
	public String getNamespace() throws InvalidRegistryObjectException;

	
Returns the namespace name for this extension.
Throws:
InvalidRegistryObjectException – if this extension is no longer valid
Returns:
the namespace name for this extension
Since:
org.eclipse.equinox.registry 3.2/**
	 * Returns the namespace name for this extension.
	 *
	 * @return the namespace name for this extension
	 * @throws InvalidRegistryObjectException if this extension is no longer valid
	 * @since org.eclipse.equinox.registry 3.2
	 */
	public String getNamespaceIdentifier() throws InvalidRegistryObjectException;

	
Returns the contributor of this extension.
Throws:
InvalidRegistryObjectException – if this extension is no longer valid
Returns:
the contributor for this extension
Since:
org.eclipse.equinox.registry 3.2/**
	 * Returns the contributor of this extension.
	 *
	 * @return the contributor for this extension
	 * @throws InvalidRegistryObjectException if this extension is no longer valid
	 * @since org.eclipse.equinox.registry 3.2
	 */
	public IContributor getContributor() throws InvalidRegistryObjectException;

	
Returns the unique identifier of the extension point
to which this extension should be contributed.
Throws:
InvalidRegistryObjectException – if this extension is no longer valid
Returns:
the unique identifier of the relevant extension point/**
	 * Returns the unique identifier of the extension point
	 * to which this extension should be contributed.
	 *
	 * @return the unique identifier of the relevant extension point
	 * @throws InvalidRegistryObjectException if this extension is no longer valid
	 */
	public String getExtensionPointUniqueIdentifier() throws InvalidRegistryObjectException;

	
Returns a displayable label for this extension.
Returns the empty string if no label for this extension
is specified in the plug-in manifest file.
 Note that any translation specified in the plug-in manifest
file is automatically applied.

Throws:
InvalidRegistryObjectException – if this extension is no longer valid
Returns:
a displayable string label for this extension,
   possibly the empty string/**
	 * Returns a displayable label for this extension.
	 * Returns the empty string if no label for this extension
	 * is specified in the plug-in manifest file.
	 * <p> Note that any translation specified in the plug-in manifest
	 * file is automatically applied.
	 * <p>
	 *
	 * @return a displayable string label for this extension,
	 *    possibly the empty string
	 * @throws InvalidRegistryObjectException if this extension is no longer valid
	 */
	public String getLabel() throws InvalidRegistryObjectException;

	
When multi-language support is enabled, this method returns a displayable label for this
extension in the specified locale. Returns the empty string if no label for this extension
is specified in the plug-in manifest file.

The locale matching tries to find the best match between available translations and
the requested locale, falling back to a more generic locale ("en") when the specific
locale ("en_US") is not available.
 If multi-language support is not enabled, this method is equivalent to the method getLabel(). 
Params:
locale – the requested locale
Throws:
InvalidRegistryObjectException – if this extension is no longer valid
See Also:
IExtensionRegistry.isMultiLanguage()
Returns:
a displayable string label for this extension,
   possibly the empty string
Since:
3.5/**
	 * When multi-language support is enabled, this method returns a displayable label for this
	 * extension in the specified locale. Returns the empty string if no label for this extension
	 * is specified in the plug-in manifest file.
	 * <p>
	 * The locale matching tries to find the best match between available translations and
	 * the requested locale, falling back to a more generic locale ("en") when the specific
	 * locale ("en_US") is not available.
	 * </p><p>
	 * If multi-language support is not enabled, this method is equivalent to the method
	 * {@link #getLabel()}.
	 * </p>
	 * @param locale the requested locale
	 * @return a displayable string label for this extension,
	 *    possibly the empty string
	 * @throws InvalidRegistryObjectException if this extension is no longer valid
	 * @see IExtensionRegistry#isMultiLanguage()
	 * @since 3.5
	 */
	public String getLabel(String locale) throws InvalidRegistryObjectException;

	
Returns the simple identifier of this extension, or null
if this extension does not have an identifier.
This identifier is specified in the plug-in manifest (plugin.xml)
file as a non-empty string containing no period characters
('.') and must be unique within the namespace.
Throws:
InvalidRegistryObjectException – if this extension is no longer valid
Returns:
the simple identifier of the extension (e.g. "main")
 or null/**
	 * Returns the simple identifier of this extension, or <code>null</code>
	 * if this extension does not have an identifier.
	 * This identifier is specified in the plug-in manifest (<code>plugin.xml</code>)
	 * file as a non-empty string containing no period characters
	 * (<code>'.'</code>) and must be unique within the namespace.
	 *
	 * @return the simple identifier of the extension (e.g. <code>"main"</code>)
	 *  or <code>null</code>
	 * @throws InvalidRegistryObjectException if this extension is no longer valid
	 */
	public String getSimpleIdentifier() throws InvalidRegistryObjectException;

	
Returns the unique identifier of this extension, or null
if this extension does not have an identifier.
If available, this identifier is unique within the plug-in registry, and
is composed of the namespace where this extension
was declared and this extension's simple identifier.
Throws:
InvalidRegistryObjectException – if this extension is no longer valid
Returns:
the unique identifier of the extension
   (e.g. "com.example.acme.main"), or null/**
	 * Returns the unique identifier of this extension, or <code>null</code>
	 * if this extension does not have an identifier.
	 * If available, this identifier is unique within the plug-in registry, and
	 * is composed of the namespace where this extension
	 * was declared and this extension's simple identifier.
	 *
	 * @return the unique identifier of the extension
	 *    (e.g. <code>"com.example.acme.main"</code>), or <code>null</code>
	 * @throws InvalidRegistryObjectException if this extension is no longer valid
	 */
	public String getUniqueIdentifier() throws InvalidRegistryObjectException;

	@Override
	public boolean equals(Object o);

	
Returns whether this extension object is valid.
Returns:
true if the object is valid, and false
if it is no longer valid
Since:
3.1/**
	 * Returns whether this extension object is valid.
	 *
	 * @return <code>true</code> if the object is valid, and <code>false</code>
	 * if it is no longer valid
	 * @since 3.1
	 */
	public boolean isValid();
}