--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/src/share/classes/com/sun/tools/javac/util/CloseableURLClassLoader.java	Fri Dec 11 14:26:27 2009 -0800
@@ -0,0 +1,108 @@
+/*
+ * Copyright 2007 Sun Microsystems, Inc.  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.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package com.sun.tools.javac.util;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.ArrayList;
+import java.util.jar.JarFile;
+
+/**
+ * A URLClassLoader that also implements Closeable.
+ * Reflection is used to access internal data structures in the URLClassLoader,
+ * since no public API exists for this purpose. Therefore this code is somewhat
+ * fragile. Caveat emptor.
+ * @throws Error if the internal data structures are not as expected.
+ *
+ *  <p><b>This is NOT part of any API supported by Sun Microsystems.  If
+ *  you write code that depends on this, you do so at your own risk.
+ *  This code and its internal interfaces are subject to change or
+ *  deletion without notice.</b>
+ */
+public class CloseableURLClassLoader
+        extends URLClassLoader implements Closeable {
+    public CloseableURLClassLoader(URL[] urls, ClassLoader parent) throws Error {
+        super(urls, parent);
+        try {
+            getLoaders(); //proactive check that URLClassLoader is as expected
+        } catch (Throwable t) {
+            throw new Error("cannot create CloseableURLClassLoader", t);
+        }
+    }
+
+    /**
+     * Close any jar files that may have been opened by the class loader.
+     * Reflection is used to access the jar files in the URLClassLoader's
+     * internal data structures.
+     * @throws java.io.IOException if the jar files cannot be found for any
+     * reson, or if closing the jar file itself causes an IOException.
+     */
+    @Override
+    public void close() throws IOException {
+        try {
+            for (Object l: getLoaders()) {
+                if (l.getClass().getName().equals("sun.misc.URLClassPath$JarLoader")) {
+                    Field jarField = l.getClass().getDeclaredField("jar");
+                    JarFile jar = (JarFile) getField(l, jarField);
+                    if (jar != null) {
+                        //System.err.println("CloseableURLClassLoader: closing " + jar);
+                        jar.close();
+                    }
+                }
+            }
+        } catch (Throwable t) {
+            IOException e = new IOException("cannot close class loader");
+            e.initCause(t);
+            throw e;
+        }
+    }
+
+    private ArrayList<?> getLoaders()
+            throws NoSuchFieldException, IllegalArgumentException, IllegalAccessException
+    {
+        Field ucpField = URLClassLoader.class.getDeclaredField("ucp");
+        Object urlClassPath = getField(this, ucpField);
+        if (urlClassPath == null)
+            throw new AssertionError("urlClassPath not set in URLClassLoader");
+        Field loadersField = urlClassPath.getClass().getDeclaredField("loaders");
+        return (ArrayList<?>) getField(urlClassPath, loadersField);
+    }
+
+    private Object getField(Object o, Field f)
+            throws IllegalArgumentException, IllegalAccessException {
+        boolean prev = f.isAccessible();
+        try {
+            f.setAccessible(true);
+            return f.get(o);
+        } finally {
+            f.setAccessible(prev);
+        }
+    }
+
+}