com.google.inject.internal.aop.ClassDefining 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.inject.internal.InternalFlags;
import com.google.inject.internal.InternalFlags.CustomClassLoadingOption;
import java.util.logging.Logger;
/**
* Entry-point for defining dynamically generated classes.
*
* @author [email protected] (Stuart McCulloch)
*/
public final class ClassDefining {
private ClassDefining() {}
private static final Logger logger = Logger.getLogger(ClassDefining.class.getName());
private static final String CLASS_DEFINING_UNSUPPORTED =
"Unsafe is not accessible and custom classloading is turned OFF.";
// initialization-on-demand...
private static class ClassDefinerHolder {
static final ClassDefiner INSTANCE = bindClassDefiner();
static final boolean IS_UNSAFE = INSTANCE instanceof UnsafeClassDefiner;
}
/** Defines a new class relative to the host. */
public static Class define(Class hostClass, byte[] bytecode) throws Exception {
return ClassDefinerHolder.INSTANCE.define(hostClass, bytecode);
}
/** Returns true if the current class definer allows access to package-private members. */
public static boolean hasPackageAccess() {
return ClassDefinerHolder.IS_UNSAFE;
}
/** Returns true if it's possible to load by name proxies defined from the given host. */
public static boolean canLoadProxyByName(Class hostClass) {
return !ClassDefinerHolder.IS_UNSAFE || UnsafeClassDefiner.canLoadProxyByName(hostClass);
}
/** Returns true if it's possible to downcast to proxies defined from the given host. */
public static boolean canDowncastToProxy(Class hostClass) {
return !ClassDefinerHolder.IS_UNSAFE || UnsafeClassDefiner.canDowncastToProxy(hostClass);
}
/** Binds the preferred {@link ClassDefiner} instance. */
static ClassDefiner bindClassDefiner() {
// ANONYMOUS acts like OFF, it picks the Unsafe definer but changes how it defines classes
CustomClassLoadingOption loadingOption = InternalFlags.getCustomClassLoadingOption();
if (loadingOption == CustomClassLoadingOption.CHILD) {
return new ChildClassDefiner(); // override default choice
} else if (UnsafeClassDefiner.isAccessible()) {
return new UnsafeClassDefiner(); // default choice if available
} else if (loadingOption != CustomClassLoadingOption.OFF) {
return new ChildClassDefiner(); // second choice unless forbidden
} else {
logger.warning(CLASS_DEFINING_UNSUPPORTED);
return (hostClass, bytecode) -> {
throw new UnsupportedOperationException(
"Cannot define class, " + CLASS_DEFINING_UNSUPPORTED);
};
}
}
}