75 lines
3.1 KiB
Java
75 lines
3.1 KiB
Java
/*
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* Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.reflect;
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import java.security.AccessController;
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import java.security.PrivilegedAction;
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import sun.misc.Unsafe;
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/** Utility class which assists in calling Unsafe.defineClass() by
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creating a new class loader which delegates to the one needed in
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order for proper resolution of the given bytecodes to occur. */
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class ClassDefiner {
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static final Unsafe unsafe = Unsafe.getUnsafe();
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/** <P> We define generated code into a new class loader which
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delegates to the defining loader of the target class. It is
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necessary for the VM to be able to resolve references to the
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target class from the generated bytecodes, which could not occur
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if the generated code was loaded into the bootstrap class
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loader. </P>
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<P> There are two primary reasons for creating a new loader
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instead of defining these bytecodes directly into the defining
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loader of the target class: first, it avoids any possible
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security risk of having these bytecodes in the same loader.
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Second, it allows the generated bytecodes to be unloaded earlier
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than would otherwise be possible, decreasing run-time
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footprint. </P>
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*/
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static Class<?> defineClass(String name, byte[] bytes, int off, int len,
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final ClassLoader parentClassLoader)
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{
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ClassLoader newLoader = AccessController.doPrivileged(
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new PrivilegedAction<ClassLoader>() {
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public ClassLoader run() {
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return new DelegatingClassLoader(parentClassLoader);
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}
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});
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return unsafe.defineClass(name, bytes, off, len, newLoader, null);
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}
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}
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// NOTE: this class's name and presence are known to the virtual
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// machine as of the fix for 4474172.
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class DelegatingClassLoader extends ClassLoader {
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DelegatingClassLoader(ClassLoader parent) {
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super(parent);
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}
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}
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