/* * Copyright (c) 1999, 2001, 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 usepublic final class FactoryEnumeration { private List 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 */ FactoryEnumeration(List factories, ClassLoader loader) { this.factories = factories; this.loader = loader; } public Object next() throws NamingException { synchronized (factories) { NamedWeakReference ref = (NamedWeakReference) 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 answer = Class.forName(className, true, loader); } // Instantiate Class to get factory answer = ((Class) answer).newInstance(); 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(); } }}
/*
* Copyright (c) 1999, 2001, 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 {
private List 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
*/
FactoryEnumeration(List factories, ClassLoader loader) {
this.factories = factories;
this.loader = loader;
}
public Object next() throws NamingException {
synchronized (factories) {
NamedWeakReference ref = (NamedWeakReference) 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
answer = Class.forName(className, true, loader);
}
// Instantiate Class to get factory
answer = ((Class) answer).newInstance();
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();
}
}
}