1 files changed, 149 insertions, 0 deletions
diff --git a/libjava/gnu/classpath/ServiceProviderLoadingAction.java b/libjava/gnu/classpath/ServiceProviderLoadingAction.java
new file mode 100644
index 0000000..4832c97
--- /dev/null
+++ b/libjava/gnu/classpath/ServiceProviderLoadingAction.java
@@ -0,0 +1,149 @@
+/* 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., 59 Temple Place, Suite 330, Boston, MA
+02111-1307 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} 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;
+  }
+}