1 /*
   2  * Copyright (c) 2018, 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 
  25 package pkg;
  26 
  27 import java.util.*;
  28 import java.io.*;
  29 
  30 // This class loader loads Foo, Child, and Grand.
  31 public class ClassLoaderForChildGrandFoo extends ClassLoader {
  32 
  33     ClassLoader l2 = null;
  34 
  35     private final Set<String> names = new HashSet<>();
  36 
  37     public ClassLoaderForChildGrandFoo(String... names) {
  38         for (String n : names) this.names.add(n);
  39     }
  40 
  41     protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
  42         // Create class loader l2 to load Parent and Foo.  And, pass this class
  43         // loader to l2 so l2 can use it to load Grand.
  44         if (name.contains("Parent") && l2 == null) {
  45             l2 = new ClassLoaderForParentFoo(this, "pkg.Foo", "pkg.Grand", "pkg.Parent");
  46             Class<?> b = l2.loadClass("pkg.Parent");
  47             return b;
  48         }
  49         if (!names.contains(name)) return super.loadClass(name, resolve);
  50         Class<?> result = findLoadedClass(name);
  51 
  52         if (result == null) {
  53             String filename = name.replace('.', '/') + ".class";
  54             try (InputStream data = getResourceAsStream(filename)) {
  55                 if (data == null) throw new ClassNotFoundException();
  56                 try (ByteArrayOutputStream buffer = new ByteArrayOutputStream()) {
  57                     int b;
  58                     do {
  59                         b = data.read();
  60                         if (b >= 0) buffer.write(b);
  61                     } while (b >= 0);
  62                     byte[] bytes = buffer.toByteArray();
  63                     result = defineClass(name, bytes, 0, bytes.length);
  64                 }
  65             } catch (IOException e) {
  66                 throw new ClassNotFoundException("Error reading class file", e);
  67             }
  68         }
  69         if (resolve) resolveClass(result);
  70         return result;
  71     }
  72 
  73 }