| /******************************************************************************* |
| * Copyright (c) 2003, 2006 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.osgi.framework.internal.core; |
| |
| import java.net.URL; |
| import java.util.Enumeration; |
| import org.eclipse.osgi.framework.util.KeyedHashSet; |
| |
| /** |
| * This class is used to optimize finding provided-packages for a bundle. |
| * If the package cannot be found in a list of required bundles then this class |
| * is used to cache a null package source so that the search does not need to |
| * be done again. |
| */ |
| public class NullPackageSource extends PackageSource { |
| static KeyedHashSet sources; |
| private NullPackageSource(String name) { |
| super(name); |
| } |
| |
| public SingleSourcePackage[] getSuppliers() { |
| return null; |
| } |
| |
| public boolean isNullSource() { |
| return true; |
| } |
| |
| public String toString() { |
| return id + " -> null"; //$NON-NLS-1$ |
| } |
| |
| public Class loadClass(String name) { |
| return null; |
| } |
| |
| public URL getResource(String name) { |
| return null; |
| } |
| |
| public Enumeration getResources(String name) { |
| return null; |
| } |
| |
| public static synchronized NullPackageSource getNullPackageSource(String name) { |
| if (sources == null) |
| sources = new KeyedHashSet(); |
| NullPackageSource result = (NullPackageSource) sources.getByKey(name); |
| if (result != null) |
| return result; |
| result = new NullPackageSource(name); |
| sources.add(result); |
| return result; |
| } |
| } |