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/*
* Copyright (c) Facebook, Inc. and its affiliates.
*
* 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.facebook.buck.util;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableList;
import java.io.IOException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.HashMap;
import java.util.Map;
import java.util.Optional;
import javax.annotation.Nullable;
/**
* Maintain a cache mapping class paths to class loaders that load from these class paths. The class
* loaders remain active until ClassLoaderCache itself is unloaded.
*/
public final class ClassLoaderCache implements AutoCloseable {
private final Map<ClassLoader, Map<ImmutableList<URL>, ClassLoader>> cache = new HashMap<>();
private int referenceCount = 1;
private synchronized Map<ImmutableList<URL>, ClassLoader> getCacheForParent(
@Nullable ClassLoader parentClassLoader) {
Map<ImmutableList<URL>, ClassLoader> cacheForParent = cache.get(parentClassLoader);
if (cacheForParent == null) {
cacheForParent = new HashMap<>();
cache.put(parentClassLoader, cacheForParent);
}
return cacheForParent;
}
public synchronized ClassLoader getClassLoaderForClassPath(
@Nullable ClassLoader parentClassLoader, ImmutableList<URL> classPath) {
Map<ImmutableList<URL>, ClassLoader> cacheForParent = getCacheForParent(parentClassLoader);
ClassLoader classLoader = cacheForParent.get(classPath);
if (classLoader == null) {
URL[] urls = classPath.toArray(new URL[0]);
classLoader = new CachedURLClassLoader(urls, parentClassLoader);
cacheForParent.put(classPath, classLoader);
}
return classLoader;
}
@VisibleForTesting
public synchronized void injectClassLoader(
@Nullable ClassLoader parentClassLoader,
ImmutableList<URL> classPath,
ClassLoader injectedClassLoader) {
Map<ImmutableList<URL>, ClassLoader> cacheForParent = getCacheForParent(parentClassLoader);
cacheForParent.put(classPath, injectedClassLoader);
}
public synchronized ClassLoaderCache addRef() {
referenceCount += 1;
return this;
}
@Override
public synchronized void close() throws IOException {
if (referenceCount > 1) {
referenceCount -= 1;
return;
}
Optional<IOException> caughtEx = Optional.empty();
for (Map<ImmutableList<URL>, ClassLoader> cacheForParent : cache.values()) {
for (ClassLoader cl : cacheForParent.values()) {
try {
if (cl instanceof CachedURLClassLoader) {
((CachedURLClassLoader) cl).reallyClose();
}
} catch (IOException ex) {
if (caughtEx.isPresent()) {
caughtEx.get().addSuppressed(ex);
} else {
caughtEx = Optional.of(ex);
}
}
}
}
if (caughtEx.isPresent()) {
throw caughtEx.get();
}
}
private static class CachedURLClassLoader extends URLClassLoader {
public CachedURLClassLoader(URL[] urls, @Nullable ClassLoader parent) {
super(urls, parent);
}
@Override
public void close() {
// Do nothing; only the cache can close this ClassLoader
}
private void reallyClose() throws IOException {
super.close();
}
}
}