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/*
* Copyright (C) 2015 The Android Open Source Project
*
* 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.android.tools.fd.runtime;
import com.android.annotations.NonNull;
import android.util.Log;
import java.io.File;
import java.lang.reflect.Field;
import java.util.List;
import dalvik.system.BaseDexClassLoader;
import static com.android.tools.fd.runtime.BootstrapApplication.LOG_TAG;
// This is based on com.google.devtools.build.android.incrementaldeployment.IncrementalClassLoader
// with some cleanup around path handling and made it compile on JDK 6 (e.g. removed multicatch
// etc)
// See
// https://github.com/google/bazel/blob/master/src/tools/android/java/com/google/devtools/build/android/incrementaldeployment/IncrementalClassLoader.java
// (May 11 revision, ca96e11)
/**
* A class loader that loads classes from any .dex file in a particular directory on the SD card.
* <p>
* <p>Used to implement incremental deployment to Android phones.
*/
public class IncrementalClassLoader extends ClassLoader {
/** When false, compiled out of runtime library */
public static final boolean DEBUG_CLASS_LOADING = false;
private final DelegateClassLoader delegateClassLoader;
public IncrementalClassLoader(
ClassLoader original, String nativeLibraryPath, String codeCacheDir, 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(nativeLibraryPath, codeCacheDir, dexes,
original);
}
@Override
public Class<?> findClass(String className) throws ClassNotFoundException {
try {
Class<?> aClass = delegateClassLoader.findClass(className);
//noinspection PointlessBooleanExpression,ConstantConditions
if (DEBUG_CLASS_LOADING && Log.isLoggable(LOG_TAG, Log.VERBOSE)) {
Log.v(LOG_TAG, "Incremental class loader: findClass(" + className + ") = " + aClass);
}
return aClass;
} catch (ClassNotFoundException e) {
//noinspection PointlessBooleanExpression,ConstantConditions
if (DEBUG_CLASS_LOADING && Log.isLoggable(LOG_TAG, Log.VERBOSE)) {
Log.v(LOG_TAG, "Incremental class loader: findClass(" + className + ") : not found");
}
throw e;
}
}
/**
* 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 {
try {
Class<?> aClass = super.findClass(name);
//noinspection PointlessBooleanExpression,ConstantConditions
if (DEBUG_CLASS_LOADING && Log.isLoggable(LOG_TAG, Log.VERBOSE)) {
Log.v(LOG_TAG, "Delegate class loader: findClass(" + name + ") = " + aClass);
}
return aClass;
} catch (ClassNotFoundException e) {
//noinspection PointlessBooleanExpression,ConstantConditions
if (DEBUG_CLASS_LOADING && Log.isLoggable(LOG_TAG, Log.VERBOSE)) {
Log.v(LOG_TAG, "Delegate class loader: findClass(" + name + ") : not found");
}
throw e;
}
}
}
private static DelegateClassLoader createDelegateClassLoader(
String nativeLibraryPath, String codeCacheDir, List<String> dexes,
ClassLoader original) {
String pathBuilder = createDexPath(dexes);
return new DelegateClassLoader(pathBuilder, new File(codeCacheDir),
nativeLibraryPath, original);
}
@NonNull
private static String createDexPath(List<String> dexes) {
StringBuilder pathBuilder = new StringBuilder();
boolean first = true;
for (String dex : dexes) {
if (first) {
first = false;
} else {
pathBuilder.append(File.pathSeparator);
}
pathBuilder.append(dex);
}
if (Log.isLoggable(LOG_TAG, Log.VERBOSE)) {
Log.v(LOG_TAG, "Incremental dex path is "
+ BootstrapApplication.join('\n', dexes));
}
return pathBuilder.toString();
}
private static void setParent(ClassLoader classLoader, ClassLoader newParent) {
try {
Field parent = ClassLoader.class.getDeclaredField("parent");
parent.setAccessible(true);
parent.set(classLoader, newParent);
} catch (IllegalArgumentException e) {
throw new RuntimeException(e);
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
} catch (NoSuchFieldException e) {
throw new RuntimeException(e);
}
}
public static ClassLoader inject(
ClassLoader classLoader, String nativeLibraryPath, String codeCacheDir,
List<String> dexes) {
IncrementalClassLoader incrementalClassLoader =
new IncrementalClassLoader(classLoader, nativeLibraryPath, codeCacheDir, dexes);
setParent(classLoader, incrementalClassLoader);
// This works as follows:
// We're given the current class loader that's used to load the bootstrap application.
// We have a new class loader which reads patches/overrides from the data directory
// instead. We want *that* class loader to have the bootstrap class loader's parent
// as its parent, and then we make the bootstrap class loader parented by our
// class loader.
//
// In other words, we have this:
// BootstrapApplication.classLoader = ClassLoader1, parent=ClassLoader2
// We create ClassLoader3 from the .dex files in the data directory, and arrange for
// the hierarchy to be like this:
// BootstrapApplication.classLoader = ClassLoader1, parent=ClassLoader3, parent=ClassLoader2
// With this approach, a class find (which should always look at the parents first) should
// find anything from ClassLoader3 before they get them from ClassLoader1.
// (Note that ClassLoader2 in the above is generally the BootClassLoader, not containing
// any classes we care about.)
return incrementalClassLoader;
}
}