| /* |
| * Copyright (c) 1999, 2011, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package com.sun.naming.internal; |
| |
| import java.util.List; |
| import javax.naming.NamingException; |
| |
| /** |
| * The FactoryEnumeration is used for returning factory instances. |
| * |
| * @author Rosanna Lee |
| * @author Scott Seligman |
| */ |
| |
| // no need to implement Enumeration since this is only for internal use |
| public final class FactoryEnumeration { |
| // List<NamedWeakReference<Class | Object>> |
| private List<NamedWeakReference<Object>> factories; |
| private int posn = 0; |
| private ClassLoader loader; |
| |
| /** |
| * Records the input list and uses it directly to satisfy |
| * hasMore()/next() requests. An alternative would have been to use |
| * an enumeration/iterator from the list, but we want to update the |
| * list so we keep the |
| * original list. The list initially contains Class objects. |
| * As each element is used, the Class object is replaced by an |
| * instance of the Class itself; eventually, the list contains |
| * only a list of factory instances and no more updates are required. |
| * |
| * <p> Both Class objects and factories are wrapped in weak |
| * references so as not to prevent GC of the class loader. Each |
| * weak reference is tagged with the factory's class name so the |
| * class can be reloaded if the reference is cleared. |
| * |
| * @param factories A non-null list |
| * @param loader The class loader of the list's contents |
| * |
| * This internal method is used with Thread Context Class Loader (TCCL), |
| * please don't expose this method as public. |
| */ |
| FactoryEnumeration(List<NamedWeakReference<Object>> factories, |
| ClassLoader loader) { |
| this.factories = factories; |
| this.loader = loader; |
| } |
| |
| public Object next() throws NamingException { |
| synchronized (factories) { |
| |
| NamedWeakReference<Object> ref = factories.get(posn++); |
| Object answer = ref.get(); |
| if ((answer != null) && !(answer instanceof Class)) { |
| return answer; |
| } |
| |
| String className = ref.getName(); |
| |
| try { |
| if (answer == null) { // reload class if weak ref cleared |
| Class<?> cls = Class.forName(className, true, loader); |
| answer = cls; |
| } |
| // Instantiate Class to get factory |
| @SuppressWarnings("deprecation") |
| Object tmp = ((Class) answer).newInstance(); |
| answer = tmp; |
| ref = new NamedWeakReference<>(answer, className); |
| factories.set(posn-1, ref); // replace Class object or null |
| return answer; |
| } catch (ClassNotFoundException e) { |
| NamingException ne = |
| new NamingException("No longer able to load " + className); |
| ne.setRootCause(e); |
| throw ne; |
| } catch (InstantiationException e) { |
| NamingException ne = |
| new NamingException("Cannot instantiate " + answer); |
| ne.setRootCause(e); |
| throw ne; |
| } catch (IllegalAccessException e) { |
| NamingException ne = new NamingException("Cannot access " + answer); |
| ne.setRootCause(e); |
| throw ne; |
| } |
| } |
| } |
| |
| public boolean hasMore() { |
| synchronized (factories) { |
| return posn < factories.size(); |
| } |
| } |
| } |