1 /* 2 * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 24 import java.util.*; 25 import java.io.*; 26 27 public class PreemptingClassLoader extends ClassLoader { 28 29 private final Set<String> names = new HashSet<>(); 30 31 public PreemptingClassLoader(String... names) { 32 for (String n : names) this.names.add(n); 33 } 34 35 protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException { 36 if (!names.contains(name)) return super.loadClass(name, resolve); 37 Class<?> result = findLoadedClass(name); 38 if (result == null) { 39 String filename = name.replace('.', '/') + ".class"; 40 try (InputStream data = getResourceAsStream(filename)) { 41 if (data == null) throw new ClassNotFoundException(); 42 try (ByteArrayOutputStream buffer = new ByteArrayOutputStream()) { 43 int b; 44 do { 45 b = data.read(); 46 if (b >= 0) buffer.write(b); 47 } while (b >= 0); 48 byte[] bytes = buffer.toByteArray(); 49 result = defineClass(name, bytes, 0, bytes.length); 50 } 51 } catch (IOException e) { 52 throw new ClassNotFoundException("Error reading class file", e); 53 } 54 } 55 if (resolve) resolveClass(result); 56 return result; 57 } 58 59 }