/* ********************************************************************** **
** Copyright notice **
** **
** (c) 2005-2009 RSSOwl Development Team **
** http://www.rssowl.org/ **
** **
** 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.rssowl.org/legal/epl-v10.html **
** **
** A copy is found in the file epl-v10.html and important notices to the **
** license from the team is found in the textfile LICENSE.txt distributed **
** in this package. **
** **
** This copyright notice MUST APPEAR in all copies of the file! **
** **
** Contributors: **
** RSSOwl Development Team - initial API and implementation **
** **
** ********************************************************************** */
package org.rssowl.core.util;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.Platform;
import org.rssowl.core.internal.Activator;
/**
* Utility class to work with the <code>IExtensionRegistry</code> of the
* platform in order to handle contributions.
*
* @author bpasero
*/
public class ExtensionUtils {
/** The RSSOwl Namespace for extension points */
public static final String RSSOWL_NAMESPACE = "org.rssowl"; //$NON-NLS-1$
/** The RSSOwl Namespace for extension points */
public static final String RSSOWL_TESTS_NAMESPACE = "org.rssowl.core.tests"; //$NON-NLS-1$
/* Attribute for executable extensions */
private static final String EXECUTABLE_ATTRIBUTE = "class"; //$NON-NLS-1$
/**
* Returns the result of creating an executable extension from the "class"
* attribute of the first contribution that matches the given extension point.
* Third-Party contributions will be chosen over the default contribution.
*
* @param extensionPoint The fully qualified identifier of the extension point
* to use (e.g. "org.rssowl.core.ApplicationLayer")
* @return Returns the result of creating an executable extension from the
* "class" attribute of the first contribution that matches the given
* extension point. Third-Party contributions will be chosen over the default
* contribution.
* @throws IllegalStateException if no contribution was found.
*/
public static Object loadSingletonExecutableExtension(String extensionPoint) {
return loadSingletonExecutableExtension(extensionPoint, null);
}
/**
* Returns the result of creating an executable extension from the "class"
* attribute of the first contribution that matches the given extension point.
* Third-Party contributions will be chosen over the default contribution. If
* no contribution is found, the default is returned if provided.
*
* @param extensionPoint The fully qualified identifier of the extension point
* to use (e.g. "org.rssowl.core.ApplicationLayer")
* @param defaultExecutable The default executable that should be returned if
* no contribution was found.
* @return Returns the result of creating an executable extension from the
* "class" attribute of the first contribution that matches the given
* extension point. Third-Party contributions will be chosen over the default
* contribution. If no contribution is found, the default is returned if
* provided.
* @throws IllegalStateException if no contribution was found and the default
* executable is <code>NULL</code>.
*/
public static Object loadSingletonExecutableExtension(String extensionPoint, Object defaultExecutable) {
IExtensionRegistry reg = Platform.getExtensionRegistry();
IConfigurationElement elements[] = reg.getConfigurationElementsFor(extensionPoint);
/* More than one contribution - Choose 3d party over our own */
if (elements.length > 1) {
for (IConfigurationElement element : elements) {
/* Let 3d-Party contributions override our contributions */
if (!element.getNamespaceIdentifier().contains(RSSOWL_NAMESPACE)) {
try {
return element.createExecutableExtension(EXECUTABLE_ATTRIBUTE);
} catch (CoreException e) {
Activator.getDefault().getLog().log(e.getStatus());
}
}
}
}
/* One Contribution or fallback if more than one Contrib matches org.rssowl */
else if (elements.length == 1) {
try {
return elements[0].createExecutableExtension(EXECUTABLE_ATTRIBUTE);
} catch (CoreException e) {
Activator.getDefault().getLog().log(e.getStatus());
}
}
/* Return default if provided */
if (defaultExecutable != null)
return defaultExecutable;
/* Indicate missing extension with Exception */
throw new IllegalStateException("Unable to load contributions for " + extensionPoint); //$NON-NLS-1$
}
}