1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * https://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.commons.beanutils2.converters;
19
20 import java.io.ByteArrayOutputStream;
21 import java.io.FileNotFoundException;
22 import java.io.IOException;
23 import java.io.InputStream;
24
25 /**
26 * A special classloader useful for testing j2ee-like scenarios.
27 *
28 * <p>
29 * In some tests we want to be able to emulate "container" frameworks, where code runs in a hierarchy of class loaders, and certain classes may be loaded by
30 * various class loaders in the hierarchy.
31 * </p>
32 *
33 * <p>
34 * Normally this is done by having certain jars or class-file-directories in the classpath of some class loaders but not others. This is quite difficult to
35 * integrate with the build process for the unit tests though; compiling certain classes and having the output go into places that is not in the default
36 * classpath for the unit tests would be a major pain.
37 * </p>
38 *
39 * <p>
40 * So this class takes a sneaky alternative approach: it can grab any class already loaded by a parent classloader and <em>reload</em> that class via this
41 * classloader. The effect is exactly as if a class (or jar file) had been present in the classpath for a container's "shared" classloader <em>and</em> been
42 * present in the component-specific classpath too, without any messing about with the way unit test code is compiled or executed.
43 */
44 public class ClassReloader extends ClassLoader {
45
46 public ClassReloader(final ClassLoader parent) {
47 super(parent);
48 }
49
50 /**
51 * Given a class already in the classpath of a parent classloader, reload that class via this classloader.
52 */
53 public Class<?> reload(final Class<?> clazz) throws FileNotFoundException, IOException {
54 final String className = clazz.getName();
55 final String classFile = className.replace('.', '/') + ".class";
56 final ByteArrayOutputStream baos = new ByteArrayOutputStream();
57 try (InputStream classStream = getParent().getResourceAsStream(classFile)) {
58
59 if (classStream == null) {
60 throw new FileNotFoundException(classFile);
61 }
62
63 final byte[] buf = new byte[1024];
64 for (;;) {
65 final int bytesRead = classStream.read(buf);
66 if (bytesRead == -1) {
67 break;
68 }
69 baos.write(buf, 0, bytesRead);
70 }
71 }
72
73 final byte[] classData = baos.toByteArray();
74
75 // now we have the raw class data, let's turn it into a class
76 final Class<?> newClass = defineClass(className, classData, 0, classData.length);
77 resolveClass(newClass);
78 return newClass;
79 }
80 }