com.google.inject.internal.aop.ChildClassDefiner Maven / Gradle / Ivy
/*
* Copyright (C) 2020 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.inject.internal.aop;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.logging.Logger;
/**
* {@link ClassDefiner} that defines classes using child {@link ClassLoader}s.
*
* @author [email protected] (Stuart McCulloch)
*/
final class ChildClassDefiner implements ClassDefiner {
private static final Logger logger = Logger.getLogger(ChildClassDefiner.class.getName());
// initialization-on-demand...
private static class SystemChildLoaderHolder {
static final ChildLoader SYSTEM_CHILD_LOADER = doPrivileged(ChildLoader::new);
}
// initialization-on-demand...
private static class ChildLoaderCacheHolder {
static final LoadingCache CHILD_LOADER_CACHE =
CacheBuilder.newBuilder()
.weakKeys()
.weakValues()
.build(CacheLoader.from(ChildClassDefiner::childLoader));
}
@Override
public Class define(Class hostClass, byte[] bytecode) throws Exception {
ClassLoader hostLoader = hostClass.getClassLoader();
ChildLoader childLoader =
hostLoader != null
? ChildLoaderCacheHolder.CHILD_LOADER_CACHE.get(hostLoader)
: SystemChildLoaderHolder.SYSTEM_CHILD_LOADER;
return childLoader.defineInChild(bytecode);
}
/** Utility method to remove doPrivileged ambiguity */
static T doPrivileged(PrivilegedAction action) {
return AccessController.doPrivileged(action);
}
/** Creates a child loader for the given host loader */
static ChildLoader childLoader(ClassLoader hostLoader) {
logger.fine("Creating a child loader for " + hostLoader);
return doPrivileged(() -> new ChildLoader(hostLoader));
}
/** Custom class loader that grants access to defineClass */
private static final class ChildLoader extends ClassLoader {
ChildLoader(ClassLoader parent) {
super(parent);
}
ChildLoader() {
// delegate to system loader
}
Class defineInChild(byte[] bytecode) {
Class type = defineClass(null, bytecode, 0, bytecode.length, null);
resolveClass(type);
return type;
}
}
}