Java tutorial
/******************************************************************************* * Copyright (c) 2003, 2004 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/epl-v10.html * * Contributors: * IBM Corporation - initial API and implementation *******************************************************************************/ package org.eclipse.core.runtime; /** * The extension registry holds the master list of all * discovered namespaces, extension points and extensions. * <p> * The extension registry can be queried, by name, for * extension points and extensions. * </p> * <p> * The various objects that describe the contents of the extension registry * ({@link IExtensionPoint}, {@link IExtension}, and {@link IConfigurationElement}) * 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 on these object except * <code>isValid()</code> will throw {@link InvalidRegistryObjectException}. * 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 if it accesses extension registry objects, * because it's at risk if plug-in are removed. Similarly, tools that analyze * or display the extension registry are vulnerable. Client code can pre-test for * invalid objects by calling <code>isValid()</code>, which never throws this exception. * However, pre-tests are usually not sufficient because of the possibility of the * extension registry 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> * Extensions and extension points are declared by generic entities called * <cite>namespaces</cite>. The only fact known about namespaces is that they * have unique string-based identifiers. One example of a namespace * is a plug-in, for which the namespace id is the plug-in id. * </p> * <p> * This interface is not intended to be implemented by clients. * </p> * @since 3.0 */ public interface IExtensionRegistry { /** * Adds the given listener for registry change events related to extension points * in the given namespace. * Has no effect if an identical listener is already registered. After * completion of this method, the given listener will be registered for events * related to extension points in the specified namespace. If no namespace * is specified, the listener will receive notifications for changes to * extension points in any namespace. * <p> * Once registered, a listener starts receiving notification of changes to * the registry. Registry change notifications are sent asynchronously. * The listener continues to receive notifications until it is removed. * </p> * @param listener the listener * @param namespace the namespace in which to listen for changes * @see IRegistryChangeListener * @see IRegistryChangeEvent * @see #removeRegistryChangeListener(IRegistryChangeListener) */ public void addRegistryChangeListener(IRegistryChangeListener listener, String namespace); /** * Adds the given listener for registry change events. * Has no effect if an identical listener is already registered. * * <p> * This method is equivalent to: * <pre> * addRegistryChangeListener(listener,null); * </pre> * </p> * * @param listener the listener * @see IRegistryChangeListener * @see IRegistryChangeEvent * @see #addRegistryChangeListener(IRegistryChangeListener, String) * @see #removeRegistryChangeListener(IRegistryChangeListener) */ public void addRegistryChangeListener(IRegistryChangeListener listener); /** * Returns all configuration elements from all extensions configured * into the identified extension point. Returns an empty array if the extension * point does not exist, has no extensions configured, or none of the extensions * contain configuration elements. * * @param extensionPointId the unique identifier of the extension point * (e.g. <code>"org.eclipse.core.resources.builders"</code>) * @return the configuration elements */ public IConfigurationElement[] getConfigurationElementsFor(String extensionPointId); /** * Returns all configuration elements from all extensions configured * into the identified extension point. Returns an empty array if the extension * point does not exist, has no extensions configured, or none of the extensions * contain configuration elements. * * @param namespace the namespace for the extension point * (e.g. <code>"org.eclipse.core.resources"</code>) * @param extensionPointName the simple identifier of the * extension point (e.g. <code>"builders"</code>) * @return the configuration elements */ public IConfigurationElement[] getConfigurationElementsFor(String namespace, String extensionPointName); /** * Returns all configuration elements from the identified extension. * Returns an empty array if the extension does not exist or * contains no configuration elements. * * @param namespace the namespace for the extension point * (e.g. <code>"org.eclipse.core.resources"</code>) * @param extensionPointName the simple identifier of the * extension point (e.g. <code>"builders"</code>) * @param extensionId the unique identifier of the extension * (e.g. <code>"com.example.acme.coolbuilder</code>) * @return the configuration elements */ public IConfigurationElement[] getConfigurationElementsFor(String namespace, String extensionPointName, String extensionId); /** * Returns the specified extension in this extension registry, * or <code>null</code> if there is no such extension. * * @param extensionId the unique identifier of the extension * (e.g. <code>"com.example.acme.coolbuilder"</code>) * @return the extension, or <code>null</code> */ public IExtension getExtension(String extensionId); /** * Returns the specified extension in this extension registry, * or <code>null</code> if there is no such extension. * The first parameter identifies the extension point, and the second * parameter identifies an extension plugged in to that extension point. * * @param extensionPointId the unique identifier of the extension point * (e.g. <code>"org.eclipse.core.resources.builders"</code>) * @param extensionId the unique identifier of the extension * (e.g. <code>"com.example.acme.coolbuilder"</code>) * @return the extension, or <code>null</code> */ public IExtension getExtension(String extensionPointId, String extensionId); /** * Returns the specified extension in this extension registry, * or <code>null</code> if there is no such extension. * The first two parameters identify the extension point, and the third * parameter identifies an extension plugged in to that extension point. * * @param namespace the namespace for the extension point * (e.g. <code>"org.eclipse.core.resources"</code>) * @param extensionPointName the simple identifier of the * extension point (e.g. <code>"builders"</code>) * @param extensionId the unique identifier of the extension * (e.g. <code>"com.example.acme.coolbuilder"</code>) * @return the extension, or <code>null</code> */ public IExtension getExtension(String namespace, String extensionPointName, String extensionId); /** * Returns the extension point with the given extension point identifier * in this extension registry, or <code>null</code> if there is no such * extension point. * * @param extensionPointId the unique identifier of the extension point * (e.g., <code>"org.eclipse.core.resources.builders"</code>) * @return the extension point, or <code>null</code> */ public IExtensionPoint getExtensionPoint(String extensionPointId); /** * Returns the extension point in this extension registry * with the given namespace and extension point simple identifier, * or <code>null</code> if there is no such extension point. * * @param namespace the namespace for the given extension point * (e.g. <code>"org.eclipse.core.resources"</code>) * @param extensionPointName the simple identifier of the * extension point (e.g. <code>" builders"</code>) * @return the extension point, or <code>null</code> */ public IExtensionPoint getExtensionPoint(String namespace, String extensionPointName); /** * Returns all extension points known to this extension registry. * Returns an empty array if there are no extension points. * * @return the extension points known to this extension registry */ public IExtensionPoint[] getExtensionPoints(); /** * Returns all extension points declared in the given namespace. Returns an empty array if * there are no extension points declared in the namespace. * * @param namespace the namespace for the extension points * (e.g. <code>"org.eclipse.core.resources"</code>) * @return the extension points in this registry declared in the given namespace */ public IExtensionPoint[] getExtensionPoints(String namespace); /** * Returns all extensions declared in the given namespace. Returns an empty array if * no extensions are declared in the namespace. * * @param namespace the namespace for the extensions * (e.g. <code>"org.eclipse.core.resources"</code>) * @return the extensions in this registry declared in the given namespace */ public IExtension[] getExtensions(String namespace); /** * Returns all namespaces where extensions and/or extension points. Returns an * empty array if there are no known extensions/extension points in this registry. * * @return all namespaces known to this registry * @since 3.0 */ //TODO This needs to be clarified. public String[] getNamespaces(); /** * Removes the given registry change listener from this registry. * Has no effect if an identical listener is not registered. * * @param listener the listener * @see IRegistryChangeListener * @see #addRegistryChangeListener(IRegistryChangeListener) * @see #addRegistryChangeListener(IRegistryChangeListener, String) */ public void removeRegistryChangeListener(IRegistryChangeListener listener); }