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// Copyright 2014 The Bazel Authors. All rights reserved.
//
// 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.devtools.build.android.incrementaldeployment;
import android.util.Log;
import dalvik.system.BaseDexClassLoader;
import java.io.File;
import java.lang.reflect.Field;
import java.util.List;
/**
* A class loader that loads classes from any .dex file in a particular directory on the SD card.
*
* <p>Used to implement incremental deployment to Android phones.
*/
public class IncrementalClassLoader extends ClassLoader {
private final DelegateClassLoader delegateClassLoader;
public IncrementalClassLoader(ClassLoader original,
String packageName, File codeCacheDir, String nativeLibDir, List<String> dexes) {
super(original.getParent());
// TODO(bazel-team): For some mysterious reason, we need to use two class loaders so that
// everything works correctly. Investigate why that is the case so that the code can be
// simplified.
delegateClassLoader = createDelegateClassLoader(codeCacheDir, nativeLibDir, dexes, original);
}
@Override
public Class<?> findClass(String className) throws ClassNotFoundException {
return delegateClassLoader.findClass(className);
}
/**
* A class loader whose only purpose is to make {@code findClass()} public.
*/
private static class DelegateClassLoader extends BaseDexClassLoader {
private DelegateClassLoader(
String dexPath, File optimizedDirectory, String libraryPath, ClassLoader parent) {
super(dexPath, optimizedDirectory, libraryPath, parent);
}
@Override
public Class<?> findClass(String name) throws ClassNotFoundException {
return super.findClass(name);
}
}
private static DelegateClassLoader createDelegateClassLoader(
File codeCacheDir, String nativeLibDir, List<String> dexes, ClassLoader original) {
StringBuilder pathBuilder = new StringBuilder();
boolean first = true;
for (String dex : dexes) {
if (first) {
first = false;
} else {
pathBuilder.append(File.pathSeparator);
}
pathBuilder.append(dex);
}
Log.v("IncrementalClassLoader", "Incremental dex path is " + pathBuilder);
Log.v("IncrementalClassLoader", "Native lib dir is " + nativeLibDir);
return new DelegateClassLoader(pathBuilder.toString(), codeCacheDir,
nativeLibDir, original);
}
private static void setParent(ClassLoader classLoader, ClassLoader newParent) {
try {
Field parent = ClassLoader.class.getDeclaredField("parent");
parent.setAccessible(true);
parent.set(classLoader, newParent);
} catch (IllegalArgumentException | IllegalAccessException | NoSuchFieldException e) {
throw new RuntimeException(e);
}
}
public static void inject(
ClassLoader classLoader, String packageName, File codeCacheDir,
String nativeLibDir, List<String> dexes) {
IncrementalClassLoader incrementalClassLoader =
new IncrementalClassLoader(classLoader, packageName, codeCacheDir, nativeLibDir, dexes);
setParent(classLoader, incrementalClassLoader);
}
}
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