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 * http://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.beanutils.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>In some tests we want to be able to emulate "container" frameworks,
29 * where code runs in a hierarchy of classloaders, and certain classes may
30 * be loaded by various classloaders in the hierarchy.</p>
31 *
32 * <p>Normally this is done by having certain jars or class-file-directories
33 * in the classpath of some classloaders but not others. This is quite
34 * difficult difficult to integrate with the build process for the unit
35 * tests though; compiling certain classes and having the output go into
36 * places that is not in the default classpath for the unit tests would be
37 * a major pain.</p>
38 *
39 * <p>So this class takes a sneaky alternative approach: it can grab any class
40 * already loaded by a parent classloader and <i>reload</i> that class via this
41 * classloader. The effect is exactly as if a class (or jar file) had been
42 * present in the classpath for a container's "shared" classloader <i>and</i>
43 * been present in the component-specific classpath too, without any messing
44 * about with the way unit test code is compiled or executed.
45 *
46 * @version $Id$
47 */
48
49 public class ClassReloader extends ClassLoader {
50 public ClassReloader(final ClassLoader parent) {
51 super(parent);
52 }
53
54 /**
55 * Given a class already in the classpath of a parent classloader,
56 * reload that class via this classloader.
57 */
58 public Class<?> reload(final Class<?> clazz) throws FileNotFoundException, IOException {
59 final String className = clazz.getName();
60 final String classFile = className.replace('.', '/') + ".class";
61 final InputStream classStream = getParent().getResourceAsStream(classFile);
62
63 if (classStream == null) {
64 throw new FileNotFoundException(classFile);
65 }
66
67 final byte[] buf = new byte[1024];
68 final ByteArrayOutputStream baos = new ByteArrayOutputStream();
69 for(;;) {
70 final int bytesRead = classStream.read(buf);
71 if (bytesRead == -1) {
72 break;
73 }
74 baos.write(buf, 0, bytesRead);
75 }
76 classStream.close();
77
78 final byte[] classData = baos.toByteArray();
79
80 // now we have the raw class data, let's turn it into a class
81 final Class<?> newClass = defineClass(className, classData, 0, classData.length);
82 resolveClass(newClass);
83 return newClass;
84 }
85 }