| /* ServiceProviderLoadingAction.java -- Action for loading plug-in services. |
| Copyright (C) 2004 Free Software Foundation |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath 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 for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
| 02110-1301 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| |
| package gnu.classpath; |
| |
| import java.security.PrivilegedExceptionAction; |
| |
| /** |
| * A privileged action for creating a new instance of a service |
| * provider. |
| * |
| * <p>Class loading and instantiation is encapsulated in a |
| * <code>PriviledgedAction</code> in order to restrict the loaded |
| * service providers to the {@link java.security.AccessControlContext} |
| * that was active when {@link |
| * gnu.classpath.ServiceFactory#lookupProviders(Class, ClassLoader)} was |
| * called, even though the actual loading is delayed to the time when the |
| * provider is actually needed. |
| * |
| * @author <a href="mailto:brawer@dandelis.ch">Sascha Brawer</a> |
| */ |
| final class ServiceProviderLoadingAction |
| implements PrivilegedExceptionAction |
| { |
| /** |
| * The interface to which the loaded service provider implementation |
| * must conform. Usually, this is a Java interface type, but it |
| * might also be an abstract class or even a concrete class. |
| */ |
| private final Class spi; |
| |
| |
| /** |
| * The fully qualified name of the class that gets loaded when |
| * this action is executed. |
| */ |
| private final String providerName; |
| |
| |
| /** |
| * The ClassLoader that gets used for loading the service provider |
| * class. |
| */ |
| private final ClassLoader loader; |
| |
| |
| /** |
| * Constructs a privileged action for loading a service provider. |
| * |
| * @param spi the interface to which the loaded service provider |
| * implementation must conform. Usually, this is a Java interface |
| * type, but it might also be an abstract class or even a concrete |
| * superclass. |
| * |
| * @param providerName the fully qualified name of the class that |
| * gets loaded when this action is executed. |
| * |
| * @param loader the ClassLoader that gets used for loading the |
| * service provider class. |
| * |
| * @throws IllegalArgumentException if <code>spi</code>, |
| * <code>providerName</code> or <code>loader</code> is |
| * <code>null</code>. |
| */ |
| ServiceProviderLoadingAction(Class spi, String providerName, |
| ClassLoader loader) |
| { |
| if (spi == null || providerName == null || loader == null) |
| throw new IllegalArgumentException(); |
| |
| this.spi = spi; |
| this.providerName = providerName; |
| this.loader = loader; |
| } |
| |
| |
| /** |
| * Loads an implementation class for a service provider, and creates |
| * a new instance of the loaded class by invoking its public |
| * no-argument constructor. |
| * |
| * @return a new instance of the class whose name was passed as |
| * <code>providerName</code> to the constructor. |
| * |
| * @throws ClassCastException if the service provider does not |
| * implement the <code>spi</code> interface that was passed to the |
| * constructor. |
| * |
| * @throws IllegalAccessException if the service provider class or |
| * its no-argument constructor are not <code>public</code>. |
| * |
| * @throws InstantiationException if the service provider class is |
| * <code>abstract</code>, an interface, a primitive type, an array |
| * class, or void; or if service provider class does not have a |
| * no-argument constructor; or if there some other problem with |
| * creating a new instance of the service provider. |
| */ |
| public Object run() |
| throws Exception |
| { |
| Class loadedClass; |
| Object serviceProvider; |
| |
| loadedClass = loader.loadClass(providerName); |
| serviceProvider = loadedClass.newInstance(); |
| |
| // Ensure that the loaded provider is actually implementing |
| // the service provider interface. |
| if (!spi.isInstance(serviceProvider)) |
| throw new ClassCastException(spi.getName()); |
| |
| return serviceProvider; |
| } |
| } |