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/*
* Copyright (c) 2013, 2020, Oracle and/or its affiliates. All rights reserved.
* 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 jdk.test.lib;
import java.security.SecureClassLoader;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/**
* {@code ByteCodeLoader} can be used for easy loading of byte code already
* present in memory.
*
* {@code InMemoryCompiler} can be used for compiling source code in a string
* into byte code, which then can be loaded with {@code ByteCodeLoader}.
*
* @see InMemoryCompiler
*/
public class ByteCodeLoader extends SecureClassLoader {
private final Map<String,byte[]> classBytesMap;
private final Map<String,Class<?>> cache;
public ByteCodeLoader(Map<String,byte[]> classBytesMap, ClassLoader parent) {
super(parent);
this.classBytesMap = classBytesMap;
cache = new ConcurrentHashMap<>();
}
/**
* Creates a new {@code ByteCodeLoader} ready to load a class with the
* given name and the given byte code, using the default parent class
* loader for delegation.
*
* @param className The name of the class
* @param byteCode The byte code of the class
*/
public ByteCodeLoader(String className, byte[] byteCode) {
super();
classBytesMap = Map.of(className, byteCode);
cache = new ConcurrentHashMap<>();
}
/**
* Creates a new {@code ByteCodeLoader} ready to load a class with the
* given name and the given byte code, using the specified parent class
* loader for delegation.
*
* @param className The name of the class
* @param byteCode The byte code of the class
* @param parent The parent class loader for delegation
*/
public ByteCodeLoader(String className, byte[] byteCode, ClassLoader parent) {
this(Map.of(className, byteCode), parent);
}
private static final Object lock = new Object();
@Override
public Class<?> loadClass(String name) throws ClassNotFoundException {
if (classBytesMap.get(name) == null) {
return super.loadClass(name);
}
Class<?> cls = cache.get(name);
if (cls != null) {
return cls;
}
synchronized (lock) {
cls = cache.get(name);
if (cls == null) {
cls = findClass(name);
cache.put(name, cls);
}
}
return cls;
}
@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {
byte[] byteCode = classBytesMap.get(name);
if (byteCode == null) {
throw new ClassNotFoundException(name);
}
return defineClass(name, byteCode, 0, byteCode.length);
}
/**
* Utility method for creating a new {@code ByteCodeLoader} and then
* directly load the given byte code.
*
* @param className The name of the class
* @param byteCode The byte code for the class
* @throws ClassNotFoundException if the class can't be loaded
* @return A {@see Class} object representing the class
*/
public static Class<?> load(String className, byte[] byteCode) throws ClassNotFoundException {
return new ByteCodeLoader(className, byteCode).loadClass(className);
}
}
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