ByteBuddyMockFactory.java

/*
 * Copyright 2023 the original author or authors.
 *
 * 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
 *
 *     https://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 org.spockframework.mock.runtime;

import net.bytebuddy.ByteBuddy;
import net.bytebuddy.TypeCache;
import net.bytebuddy.description.modifier.SynchronizationState;
import net.bytebuddy.description.modifier.SyntheticState;
import net.bytebuddy.description.modifier.Visibility;
import net.bytebuddy.dynamic.Transformer;
import net.bytebuddy.dynamic.loading.ClassInjector;
import net.bytebuddy.dynamic.loading.ClassLoadingStrategy;
import net.bytebuddy.dynamic.scaffold.TypeValidation;
import net.bytebuddy.implementation.FieldAccessor;
import net.bytebuddy.implementation.MethodDelegation;
import net.bytebuddy.implementation.bind.annotation.Morph;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.VisibleForTesting;
import org.spockframework.mock.ISpockMockObject;
import org.spockframework.mock.codegen.Target;
import org.spockframework.util.Nullable;

import java.lang.reflect.Method;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ThreadLocalRandom;

import static net.bytebuddy.matcher.ElementMatchers.any;
import static net.bytebuddy.matcher.ElementMatchers.none;

class ByteBuddyMockFactory {
  /**
   * The mask to use to mask out the {@link TypeCache.SimpleKey#hashCode()} to find the {@link #cacheLocks}.
   */
  private static final int CACHE_LOCK_MASK = 0x0F;

  /**
   * The size of the {@link #cacheLocks}.
   */
  private static final int CACHE_LOCK_SIZE = CACHE_LOCK_MASK + 1;

  private static final Class<?> CODEGEN_TARGET_CLASS = Target.class;
  private static final String CODEGEN_PACKAGE = CODEGEN_TARGET_CLASS.getPackage().getName();

  /**
   * This array contains {@link TypeCachingLock} instances, which are used as java monitor locks for
   * {@link TypeCache#findOrInsert(ClassLoader, Object, Callable, Object)}.
   * The {@code cacheLocks} spreads the lock to acquire over multiple locks instead of using a single lock
   * {@code CACHE} for all {@link TypeCache.SimpleKey}s.
   *
   * <p>Note: We can't simply use the mockedType class lock as a lock,
   * because the {@code TypeCache.SimpleKey}, will be the same for different {@code mockTypes + additionalInterfaces}.
   * See the {@code hashCode} implementation of the {@code TypeCache.SimpleKey}, which has {@code Set} semantics.
   */
  private final TypeCachingLock[] cacheLocks;

  private final TypeCache<TypeCache.SimpleKey> CACHE =
    new TypeCache.WithInlineExpunction<>(TypeCache.Sort.SOFT);

  ByteBuddyMockFactory() {
    cacheLocks = new TypeCachingLock[CACHE_LOCK_SIZE];
    for (int i = 0; i < CACHE_LOCK_SIZE; i++) {
      cacheLocks[i] = new TypeCachingLock();
    }
  }

  Object createMock(final Class<?> type,
                           final List<Class<?>> additionalInterfaces,
                           @Nullable List<Object> constructorArgs,
                           IProxyBasedMockInterceptor interceptor,
                           final ClassLoader classLoader,
                           boolean useObjenesis) {

    TypeCache.SimpleKey key = new TypeCache.SimpleKey(type, additionalInterfaces);

    Class<?> enhancedType = CACHE.findOrInsert(classLoader,
      key,
      () -> {
        String typeName = type.getName();
        Class<?> targetClass = type;
        if (shouldLoadIntoCodegenPackage(type)) {
          typeName = CODEGEN_PACKAGE + "." + type.getSimpleName();
          targetClass = CODEGEN_TARGET_CLASS;
        }
        int randomNumber = Math.abs(ThreadLocalRandom.current().nextInt());
        String name = String.format("%s$%s$%d", typeName, "SpockMock", randomNumber);
        ClassLoadingStrategy<ClassLoader> strategy = determineBestClassLoadingStrategy(targetClass);
        return new ByteBuddy()
          .with(TypeValidation.DISABLED) // https://github.com/spockframework/spock/issues/776
          .ignore(none())
          .subclass(type)
          .name(name)
          .implement(additionalInterfaces)
          .implement(ISpockMockObject.class)
          .method(any())
          .intercept(MethodDelegation.withDefaultConfiguration()
            .withBinders(Morph.Binder.install(ByteBuddyInvoker.class))
            .to(ByteBuddyInterceptorAdapter.class))
          .transform(Transformer.ForMethod.withModifiers(SynchronizationState.PLAIN, Visibility.PUBLIC)) // Overridden methods should be public and non-synchronized.
          .implement(ByteBuddyInterceptorAdapter.InterceptorAccess.class)
          .intercept(FieldAccessor.ofField("$spock_interceptor"))
          .defineField("$spock_interceptor", IProxyBasedMockInterceptor.class, Visibility.PRIVATE, SyntheticState.SYNTHETIC)
          .make()
          .load(classLoader, strategy)
          .getLoaded();
      }, getCacheLockForKey(key));

    Object proxy = MockInstantiator.instantiate(type, enhancedType, constructorArgs, useObjenesis);
    ((ByteBuddyInterceptorAdapter.InterceptorAccess) proxy).$spock_set(interceptor);
    return proxy;
  }

  /**
   * Returns a {@link TypeCachingLock}, which locks the {@link TypeCache#findOrInsert(ClassLoader, Object, Callable, Object)}.
   *
   * @param key the key to lock
   * @return the {@link TypeCachingLock} to use to lock the {@link TypeCache}
   */
  private TypeCachingLock getCacheLockForKey(TypeCache.SimpleKey key) {
    int hashCode = key.hashCode();
    // Try to spread some higher bits with XOR to lower bits, because we only use lower bits.
    hashCode = hashCode ^ (hashCode >>> 16);
    int index = hashCode & CACHE_LOCK_MASK;
    return cacheLocks[index];
  }

  // This method and the ones it calls are inspired by similar code in Mockito's SubclassBytecodeGenerator
  private static boolean shouldLoadIntoCodegenPackage(Class<?> type) {
    return isComingFromJDK(type) || isComingFromSignedJar(type) || isComingFromSealedPackage(type);
  }

  private static boolean isComingFromJDK(Class<?> type) {
    // Try to read Implementation-Title entry from manifest which isn't present in every JDK JAR
    return type.getPackage() != null && "Java Runtime Environment".equalsIgnoreCase(type.getPackage().getImplementationTitle())
      || type.getName().startsWith("java.")
      || type.getName().startsWith("javax.");
  }

  private static boolean isComingFromSealedPackage(Class<?> type) {
    return type.getPackage() != null && type.getPackage().isSealed();
  }

  private static boolean isComingFromSignedJar(Class<?> type) {
    return type.getSigners() != null;
  }

  @NotNull
  private static ClassLoadingStrategy<ClassLoader> determineBestClassLoadingStrategy(Class<?> targetClass) throws Exception {
    if (ClassInjector.UsingLookup.isAvailable()) {
      Class<?> methodHandlesClass = Class.forName("java.lang.invoke.MethodHandles");
      Class<?> lookupClass = Class.forName("java.lang.invoke.MethodHandles$Lookup");
      Method lookupMethod = methodHandlesClass.getMethod("lookup");
      Method privateLookupInMethod = methodHandlesClass.getMethod("privateLookupIn", Class.class, lookupClass);
      Object lookup = lookupMethod.invoke(null);
      Object privateLookup = privateLookupInMethod.invoke(null, targetClass, lookup);
      return ClassLoadingStrategy.UsingLookup.of(privateLookup);
    }
    if (ClassInjector.UsingReflection.isAvailable()) {
      return ClassLoadingStrategy.Default.INJECTION;
    }
    return ClassLoadingStrategy.Default.WRAPPER;
  }

  private static final class TypeCachingLock {
  }
}