bundles/org.eclipse.core.runtime/src/org/eclipse/core/internal/runtime/AdapterFactoryProxy.java

/**********************************************************************
 * Copyright (c) 2004 IBM Corporation and others. All rights reserved.   This
 * program and the accompanying materials are made available under the terms of
 * the Common Public License v1.0 which accompanies this distribution, and is
 * available at http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors: 
 * IBM - Initial API and implementation
 **********************************************************************/
package org.eclipse.core.internal.runtime;

import java.util.ArrayList;
import org.eclipse.core.runtime.*;
import org.osgi.framework.Bundle;

/**
 * Instances of this class represent adapter factories that have been
 * contributed via the adapters extension point. The concrete factory is not
 * loaded until the factory's plugin is loaded, AND until the factory is
 * requested to supply an adapter.
 */
class AdapterFactoryProxy implements IAdapterFactory {
	private IConfigurationElement element;
	/**
	 * The real factory. Null until the factory is loaded.
	 */
	private IAdapterFactory factory;
	private boolean factoryLoaded = false;

	/**
	 * Creates a new factory proxy based on the given configuration element.
	 * Returns the new proxy, or null if the element could not be created.
	 */
	public static AdapterFactoryProxy createProxy(IConfigurationElement element) {
		AdapterFactoryProxy result = new AdapterFactoryProxy();
		result.element = element;
		if ("factory".equals(element.getName())) //$NON-NLS-1$
			return result;
		result.logError();
		return null;
	}

	String getAdaptableType() {
		//cannot return null because it can cause startup failure
		String result = element.getAttribute("adaptableType"); //$NON-NLS-1$
		if (result != null)
			return result;
		logError();
		return ""; //$NON-NLS-1$
	}

	public Object getAdapter(Object adaptableObject, Class adapterType) {
		if (!factoryLoaded)
			loadFactory(false);
		return factory == null ? null : factory.getAdapter(adaptableObject, adapterType);
	}

	public Class[] getAdapterList() {
		if (!factoryLoaded)
			loadFactory(false);
		return factory == null ? null : factory.getAdapterList();
	}

	String[] getAdapterNames() {
		IConfigurationElement[] children = element.getChildren();
		ArrayList adapters = new ArrayList(children.length);
		for (int i = 0; i < children.length; i++) {
			//ignore unknown children for forward compatibility
			if ("adapter".equals(children[i].getName())) { //$NON-NLS-1$
				String type = children[i].getAttribute("type"); //$NON-NLS-1$
				if (type != null)
					adapters.add(type);
			}
		}
		if (adapters.isEmpty())
			logError();
		return (String[]) adapters.toArray(new String[adapters.size()]);
	}

	IExtension getExtension() {
		return element.getDeclaringExtension();
	}

	/**
	 * Loads the real adapter factory, but only if its associated plug-in is
	 * already loaded. Returns the real factory if it was successfully loaded.
	 * @param force if <code>true</code> the plugin providing the 
	 * factory will be loaded if necessary, otherwise no plugin activations
	 * will occur.
	 */
	IAdapterFactory loadFactory(boolean force) {
		synchronized (this) {
			if (factory != null || factoryLoaded)
				return factory;
			String bundleId = element.getDeclaringExtension().getNamespace();
			if (!force && Platform.getBundle(bundleId).getState() != Bundle.ACTIVE)
				return null;
			//set to true to prevent repeated attempts to load a broken factory
			factoryLoaded = true;
		}
		try {
			factory = (IAdapterFactory) element.createExecutableExtension("class"); //$NON-NLS-1$
		} catch (CoreException e) {
			InternalPlatform.getDefault().log(e.getStatus());
		}
		return factory;
	}

	/**
	 * The factory extension was malformed. Log an appropriate exception
	 */
	private void logError() {
		String msg = Policy.bind("adapters.badAdapterFactory", element.getDeclaringExtension().getNamespace()); //$NON-NLS-1$
		InternalPlatform.getDefault().log(new Status(IStatus.ERROR, Platform.PI_RUNTIME, 1, msg, null));
	}
}