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/*
* Copyright (c) 2018 by SAP AG, Walldorf, Germany.
* 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.
*
* 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
package test;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.security.SecureClassLoader;
import java.util.Arrays;
import java.util.HashSet;
import java.util.stream.Collectors;
/**
* This is a class loader which can load the same classes as another class loader.
* <p>
* This is mainly useful for tests when you want to load a class, but do it with a class
* loader you can dispose. The clone loader just asks the loader to be cloned to get
* the bytecodes, but defines the class itself.
* <p>
* Additionally you can specify a set of classes the loader should not be able to load.
*/
public class IAE_Loader2 extends SecureClassLoader {
/**
* The class loaded to clone.
*/
private final ClassLoader toClone;
/**
* The strings we cannot load.
*/
private final HashSet<String> notLoadable;
/**
* The strings we just delegate.
*/
private final HashSet<String> simpleDelegate;
/**
* Creates a class loader which can load the same classes as the loader which
* loaded the <code>IAE_Loader2</code> class itself.
* <p>
* Only the classes which are loadable by the 'parent' loader are delegated to that
* loader (to make it possible mix classes).
*
* @param name the name of the class loader.
* @param parent the parent loader which is first asked to load a class.
* @param toClone the class loader to mimic. The clone class loader will be able to
* load the same classes as the 'toClone' loader.
* @param notLoadable The classes we should not be able to load via this loader.
* @param simpleDelegate The names of the classes for which we simply delegate.
*/
public IAE_Loader2(String name, ClassLoader parent, ClassLoader toClone,
String[] notLoadable, String[] simpleDelegate) {
super(name, parent);
this.toClone = toClone;
this.notLoadable = Arrays.stream(notLoadable).collect(Collectors.toCollection(HashSet<String>::new));
this.simpleDelegate = Arrays.stream(simpleDelegate).collect(Collectors.toCollection(HashSet<String>::new));
}
/**
* @see java.lang.ClassLoader#findClass(java.lang.String)
*/
@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {
if (notLoadable.contains(name)) {
throw new ClassNotFoundException("The clone class loader explicitely " +
"didn't found the class");
}
if (simpleDelegate.contains(name)) {
return toClone.loadClass(name);
}
// We just ask the wrapper class loader to find the resource for us
URL res = toClone.getResource(name.replace('.', '/') + ".class");
if (res == null) {
throw new ClassNotFoundException(name);
}
try {
InputStream is = res.openStream();
byte[] code = readStreamIntoBuffer(is, 8192);
is.close();
return defineClass(name, code, 0, code.length);
} catch (IOException e) {
throw new ClassNotFoundException(name, e);
}
}
/**
* Reads all data of a stream into a byte array. The method allocates as
* much memory as necessary to put the whole data into that byte
* array. The data is read in chunks of <code>chunkSize</code>
* chunks.<br><br>
* <b>Implementation Note: </b> The data is read in chunks of
* <code>chunkSize</code> bytes. The data is copied to the result
* array. The memory consumption at the end of the reading is
* <code>2 x [size of resulting array] + chunkSize</code>.
*
* @param is the stream to read the data from
* @param chunkSize the size of the chunks the data should be read in
* @return the <b>whole</b> data of the stream read into an byte array
* @throws IllegalArgumentException if chunkSize <= 0
* @throws NullPointerException if is == null
* @throws IOException thrown if the provided stream encounters IO problems
*/
public static byte[] readStreamIntoBuffer(InputStream is, int chunkSize)
throws IOException {
// Check preconditions.
if (chunkSize <= 0) {
throw new IllegalArgumentException("chunkSize <= 0");
}
else if (is == null) {
throw new NullPointerException("is is null");
}
// Temporary buffer for read operations and result buffer.
byte[] tempBuffer = new byte[chunkSize];
byte[] buffer = new byte[0];
int bytesRead = 0; // bytes actual read
int oldSize = 0; // size of the resulting buffer
while ((bytesRead = is.read(tempBuffer)) > 0) {
// Temporary reference to the buffer for the copy operation.
byte[] oldBuffer = buffer;
// Create a new buffer with the size needed and copy data.
buffer = new byte[oldSize + bytesRead];
System.arraycopy(oldBuffer, 0, buffer, 0, oldBuffer.length);
// Copy the new data.
System.arraycopy(tempBuffer, 0, buffer, oldSize, bytesRead);
oldSize += bytesRead;
}
return buffer;
}
}
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