com.google.inject.internal.aop.MethodPartition 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 static java.lang.reflect.Modifier.FINAL;
import com.google.inject.TypeLiteral;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Consumer;
/**
* Accumulates methods with the same name and number of parameters. This helps focus the search for
* bridge delegates that involve type-erasure of generic parameter types, since the parameter count
* will be the same for the bridge method and its delegate.
*
* @author [email protected] (Stuart McCulloch)
*/
final class MethodPartition {
/** Reverse order of declaration; super-methods appear later in the list. */
private final List candidates = new ArrayList<>();
/** Each partition starts off with at least two methods. */
public MethodPartition(Method first, Method second) {
candidates.add(first);
candidates.add(second);
}
/** Add a new method to this partition for resolution. */
public MethodPartition addCandidate(Method method) {
candidates.add(method);
return this;
}
/**
* Resolve and collect enhanceable methods into the given list; one per method-signature. Methods
* declared in sub-classes are preferred over those in super-classes with the same signature.
* (Unless it's a bridge method, in which case we prefer to report the non-bridge method from the
* super-class as a convenience to AOP method matchers that always ignore synthetic methods.)
*
* At the same time we use generic type resolution to match resolved bridge methods to the
* methods they delegate to (this avoids the need to crack open the original class resource for
* in-depth analysis by ASM, especially since the class bytes might not be accessible.)
*/
public void collectEnhanceableMethods(
TypeLiteral hostType,
Consumer methodVisitor,
Map bridgeDelegates) {
Map leafMethods = new HashMap<>();
Map bridgeTargets = new HashMap<>();
// First resolve the 'leaf' methods; these represent the latest declaration of each method in
// the class hierarchy (ie. ignoring super-class declarations with the same parameter types)
for (Method candidate : candidates) {
String parametersKey = parametersKey(candidate.getParameterTypes());
Method existingLeafMethod = leafMethods.putIfAbsent(parametersKey, candidate);
if (existingLeafMethod == null) {
if (candidate.isBridge()) {
// Record that we've started looking for the bridge's delegate
bridgeTargets.put(parametersKey, null);
}
} else if (existingLeafMethod.isBridge()) {
// Are we looking at another method with identical parameters in the leaf class?
if (existingLeafMethod.getDeclaringClass() == candidate.getDeclaringClass()) {
if (!candidate.isBridge()) {
// Leaf has a matching non-bridge method; choose that as the method to enhance
leafMethods.put(parametersKey, candidate);
bridgeTargets.remove(parametersKey);
} else if (existingLeafMethod
.getReturnType()
.isAssignableFrom(candidate.getReturnType())) {
// Leaf has multiple matching bridge methods; choose the more specific return type
leafMethods.put(parametersKey, candidate);
}
} else if (!candidate.isBridge()) {
// Found potential bridge delegate in superclass with identical parameters
bridgeTargets.putIfAbsent(parametersKey, candidate);
}
}
}
// Discard any 'final' methods, as they cannot be enhanced, and report non-bridge leaf methods
for (Map.Entry methodEntry : leafMethods.entrySet()) {
Method method = methodEntry.getValue();
if ((method.getModifiers() & FINAL) != 0) {
bridgeTargets.remove(methodEntry.getKey());
} else if (!method.isBridge()) {
methodVisitor.accept(method);
}
}
// This leaves bridge methods which need further resolution; specifically around finding the
// real bridge delegate so we can call it using invokevirtual from our enhanced method rather
// than relying on super-class invocation to the original bridge method (as this would bypass
// interception if the delegate method was itself intercepted by a different interceptor!)
for (Map.Entry targetEntry : bridgeTargets.entrySet()) {
Method originalBridge = leafMethods.get(targetEntry.getKey());
Method superTarget = targetEntry.getValue();
Method enhanceableMethod = originalBridge;
// scan all methods looking for the bridge delegate by comparing generic parameters
// (these are the kind of bridge methods that were added to account for type-erasure)
for (Method candidate : candidates) {
if (!candidate.isBridge()) {
@SuppressWarnings("ReferenceEquality")
boolean sameMethod = candidate == superTarget;
if (sameMethod) {
// if we haven't matched our bridge by generic type and our non-bridge super-method has
// identical parameters and return type to the original (and isn't from an interface)
// then ignore the original bridge method and enhance the super-method instead - this
// helps improve interception behaviour when AOP matchers skip all synthetic methods
if (originalBridge.getReturnType() == superTarget.getReturnType()
&& !superTarget.getDeclaringClass().isInterface()) {
enhanceableMethod = superTarget;
}
break; // we've reached the non-bridge super-method so default to super-class invocation
}
// compare bridge method against resolved candidate
if (resolvedParametersMatch(originalBridge, hostType, candidate)
|| (superTarget != null
// compare candidate against resolved super-method
&& resolvedParametersMatch(candidate, hostType, superTarget))) {
// found a bridge target that differs by raw types but matches after generic resolution;
// record this delegation so we can call it from our enhanced method with invokevirtual
bridgeDelegates.put(originalBridge, candidate);
break;
}
}
}
// bridge methods aren't typically final, but just in case...
if ((enhanceableMethod.getModifiers() & FINAL) == 0) {
methodVisitor.accept(enhanceableMethod);
}
}
}
/** Each method is uniquely identified in the partition by its actual parameter types. */
private static String parametersKey(Class[] parameterTypes) {
StringBuilder key = new StringBuilder();
for (int i = 0, len = parameterTypes.length; i < len; i++) {
if (i > 0) {
key.append(',');
}
key.append(parameterTypes[i].getName());
}
return key.toString();
}
/** Compares a sub-method with a generic super-method by resolving it against the host class. */
private static boolean resolvedParametersMatch(
Method subMethod, TypeLiteral host, Method superMethod) {
Class[] parameterTypes = subMethod.getParameterTypes();
List> resolvedTypes = host.getParameterTypes(superMethod);
for (int i = 0, len = parameterTypes.length; i < len; i++) {
if (parameterTypes[i] != resolvedTypes.get(i).getRawType()) {
return false;
}
}
return true;
}
}