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/*
* 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 com.google.inject.internal.BytecodeGen.ENHANCER_BY_GUICE_MARKER;
import static com.google.inject.internal.aop.BytecodeTasks.box;
import static com.google.inject.internal.aop.BytecodeTasks.loadArgument;
import static com.google.inject.internal.aop.BytecodeTasks.packArguments;
import static com.google.inject.internal.aop.BytecodeTasks.pushInteger;
import static com.google.inject.internal.aop.BytecodeTasks.unbox;
import static com.google.inject.internal.aop.BytecodeTasks.unpackArguments;
import static java.lang.reflect.Modifier.ABSTRACT;
import static java.lang.reflect.Modifier.FINAL;
import static java.lang.reflect.Modifier.NATIVE;
import static java.lang.reflect.Modifier.PRIVATE;
import static java.lang.reflect.Modifier.PUBLIC;
import static java.lang.reflect.Modifier.STATIC;
import static java.lang.reflect.Modifier.SYNCHRONIZED;
import static org.objectweb.asm.ClassWriter.COMPUTE_MAXS;
import static org.objectweb.asm.Opcodes.AALOAD;
import static org.objectweb.asm.Opcodes.ACC_SUPER;
import static org.objectweb.asm.Opcodes.ACONST_NULL;
import static org.objectweb.asm.Opcodes.ALOAD;
import static org.objectweb.asm.Opcodes.ARETURN;
import static org.objectweb.asm.Opcodes.CHECKCAST;
import static org.objectweb.asm.Opcodes.DUP;
import static org.objectweb.asm.Opcodes.GETFIELD;
import static org.objectweb.asm.Opcodes.H_INVOKESTATIC;
import static org.objectweb.asm.Opcodes.INVOKEINTERFACE;
import static org.objectweb.asm.Opcodes.INVOKESPECIAL;
import static org.objectweb.asm.Opcodes.INVOKESTATIC;
import static org.objectweb.asm.Opcodes.INVOKEVIRTUAL;
import static org.objectweb.asm.Opcodes.IRETURN;
import static org.objectweb.asm.Opcodes.NEW;
import static org.objectweb.asm.Opcodes.PUTFIELD;
import static org.objectweb.asm.Opcodes.PUTSTATIC;
import static org.objectweb.asm.Opcodes.RETURN;
import static org.objectweb.asm.Opcodes.SWAP;
import static org.objectweb.asm.Opcodes.V1_8;
import java.lang.invoke.MethodHandle;
import java.lang.reflect.Constructor;
import java.lang.reflect.Executable;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Handle;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Type;
/**
* Generates enhanced classes.
*
* Each enhancer has the same number of constructors as the class it enhances, but each
* constructor takes an additional handler array before the rest of the expected arguments.
*
*
Enhanced methods are overridden to call the handler with the same index as the method. The
* handler delegates to the interceptor stack. Once the last interceptor returns the handler will
* call back into the trampoline with the method index, which invokes the superclass method.
*
*
The trampoline also provides access to constructor invokers that take a context object (the
* handler array) with an argument array and invokes the appropriate enhanced constructor. These
* invokers are used in the proxy factory to create enhanced instances.
*
*
Enhanced classes have the following pseudo-Java structure:
*
*
* public class HostClass$$EnhancerByGuice
* extends HostClass
* {
* // InterceptorStackCallbacks, one per enhanced method
* private final InvocationHandler[] GUICE$HANDLERS;
*
* public HostClass$$EnhancerByGuice(InvocationHandler[] handlers, ...) {
* // JVM lets us store this before calling the superclass constructor
* GUICE$HANDLERS = handlers;
* super(...);
* }
*
* public static Object GUICE$TRAMPOLINE(int index, Object context, Object[] args) {
* switch (index) {
* case 0: {
* return new HostClass$$EnhancerByGuice((InvocationHandler[]) context, ...);
* }
* case 1: {
* return context.super.instanceMethod(...); // call original unenhanced method
* }
* }
* return null;
* }
*
* // enhanced method
* public final Object instanceMethod(...) {
* // pack arguments and trigger the associated InterceptorStackCallback
* return GUICE$HANDLERS[0].invoke(this, null, args);
* }
*
* // ...
* }
*
*
* @author [email protected] (Stuart McCulloch)
*/
final class Enhancer extends AbstractGlueGenerator {
private static final String HANDLERS_NAME = "GUICE$HANDLERS";
private static final String HANDLERS_DESCRIPTOR = "[Ljava/lang/reflect/InvocationHandler;";
private static final String HANDLER_TYPE = Type.getInternalName(InvocationHandler.class);
private static final String HANDLER_ARRAY_TYPE = Type.getInternalName(InvocationHandler[].class);
private static final String INVOKERS_NAME = "GUICE$INVOKERS";
private static final String INVOKERS_DESCRIPTOR = "Ljava/lang/invoke/MethodHandle;";
private static final String CALLBACK_DESCRIPTOR =
"(Ljava/lang/Object;"
+ "Ljava/lang/reflect/Method;"
+ "[Ljava/lang/Object;)"
+ "Ljava/lang/Object;";
// Describes the LambdaMetafactory.metafactory method arguments and return type
private static final String METAFACTORY_DESCRIPTOR =
"(Ljava/lang/invoke/MethodHandles$Lookup;"
+ "Ljava/lang/String;"
+ "Ljava/lang/invoke/MethodType;"
+ "Ljava/lang/invoke/MethodType;"
+ "Ljava/lang/invoke/MethodHandle;"
+ "Ljava/lang/invoke/MethodType;)"
+ "Ljava/lang/invoke/CallSite;";
private static final Type INDEX_TO_INVOKER_METHOD_TYPE =
Type.getMethodType("(I)Ljava/util/function/BiFunction;");
private static final Type RAW_INVOKER_METHOD_TYPE =
Type.getMethodType("(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;");
private static final Type INVOKER_METHOD_TYPE =
Type.getMethodType("(Ljava/lang/Object;[Ljava/lang/Object;)Ljava/lang/Object;");
private final Map bridgeDelegates;
private final String checkcastToProxy;
Enhancer(Class hostClass, Map bridgeDelegates) {
super(hostClass, ENHANCER_BY_GUICE_MARKER);
this.bridgeDelegates = bridgeDelegates;
// with defineAnonymousClass we can't downcast to the proxy and must use host instead
this.checkcastToProxy = ClassDefining.canDowncastToProxy(hostClass) ? proxyName : hostName;
}
@Override
protected byte[] generateGlue(Collection members) {
ClassWriter cw = new ClassWriter(COMPUTE_MAXS);
// target Java8 because that's all we need for the generated trampoline code
cw.visit(V1_8, PUBLIC | ACC_SUPER, proxyName, null, hostName, null);
cw.visitSource(GENERATED_SOURCE, null);
// this shared field either contains the trampoline or glue to make it into an invoker table
cw.visitField(PUBLIC | STATIC | FINAL, INVOKERS_NAME, INVOKERS_DESCRIPTOR, null, null)
.visitEnd();
setupInvokerTable(cw);
generateTrampoline(cw, members);
// this field will hold the handlers configured for this particular enhanced instance
cw.visitField(PRIVATE | FINAL, HANDLERS_NAME, HANDLERS_DESCRIPTOR, null, null).visitEnd();
Set remainingBridgeMethods = new HashSet<>(bridgeDelegates.keySet());
int methodIndex = 0;
for (Executable member : members) {
if (member instanceof Constructor) {
enhanceConstructor(cw, (Constructor) member);
} else {
enhanceMethod(cw, (Method) member, methodIndex++);
remainingBridgeMethods.remove(member);
}
}
// replace any remaining bridge methods with virtual dispatch to their non-bridge targets
for (Method method : remainingBridgeMethods) {
Method target = bridgeDelegates.get(method);
if (target != null) {
generateVirtualBridge(cw, method, target);
}
}
cw.visitEnd();
return cw.toByteArray();
}
/** Generate static initializer to setup invoker table based on the trampoline. */
private void setupInvokerTable(ClassWriter cw) {
MethodVisitor mv = cw.visitMethod(PRIVATE | STATIC, "", "()V", null, null);
mv.visitCode();
Handle trampolineHandle =
new Handle(H_INVOKESTATIC, proxyName, TRAMPOLINE_NAME, TRAMPOLINE_DESCRIPTOR, false);
if (ClassDefining.canLoadProxyByName(hostClass)) {
// generate lambda glue to make the raw trampoline look like an invoker table
mv.visitMethodInsn(
INVOKESTATIC,
"java/lang/invoke/MethodHandles",
"lookup",
"()Ljava/lang/invoke/MethodHandles$Lookup;",
false);
mv.visitLdcInsn("apply");
mv.visitLdcInsn(INDEX_TO_INVOKER_METHOD_TYPE);
mv.visitLdcInsn(RAW_INVOKER_METHOD_TYPE);
mv.visitLdcInsn(trampolineHandle);
mv.visitLdcInsn(INVOKER_METHOD_TYPE);
mv.visitMethodInsn(
INVOKESTATIC,
"java/lang/invoke/LambdaMetafactory",
"metafactory",
METAFACTORY_DESCRIPTOR,
false);
mv.visitMethodInsn(
INVOKEVIRTUAL,
"java/lang/invoke/CallSite",
"getTarget",
"()Ljava/lang/invoke/MethodHandle;",
false);
} else {
// proxy class is hidden so we can't create our lambda glue, store raw trampoline instead
mv.visitLdcInsn(trampolineHandle);
}
mv.visitFieldInsn(PUTSTATIC, proxyName, INVOKERS_NAME, INVOKERS_DESCRIPTOR);
mv.visitInsn(RETURN);
mv.visitMaxs(0, 0);
mv.visitEnd();
}
/** Generate enhanced constructor that takes a handler array along with the expected arguments. */
private void enhanceConstructor(ClassWriter cw, Constructor constructor) {
String descriptor = Type.getConstructorDescriptor(constructor);
String enhancedDescriptor = '(' + HANDLERS_DESCRIPTOR + descriptor.substring(1);
MethodVisitor mv =
cw.visitMethod(PUBLIC, "", enhancedDescriptor, null, exceptionNames(constructor));
mv.visitCode();
mv.visitVarInsn(ALOAD, 0);
mv.visitInsn(DUP);
mv.visitVarInsn(ALOAD, 1);
// store handlers before invoking the superclass constructor (JVM allows this)
mv.visitFieldInsn(PUTFIELD, proxyName, HANDLERS_NAME, HANDLERS_DESCRIPTOR);
int slot = 2;
for (Class parameterType : constructor.getParameterTypes()) {
slot += loadArgument(mv, parameterType, slot);
}
mv.visitMethodInsn(INVOKESPECIAL, hostName, "", descriptor, false);
mv.visitInsn(RETURN);
mv.visitMaxs(0, 0);
mv.visitEnd();
}
/** Generate enhanced method that calls the handler with the same index. */
private void enhanceMethod(ClassWriter cw, Method method, int methodIndex) {
MethodVisitor mv =
cw.visitMethod(
FINAL | (method.getModifiers() & ~(ABSTRACT | NATIVE | SYNCHRONIZED)),
method.getName(),
Type.getMethodDescriptor(method),
null,
exceptionNames(method));
mv.visitVarInsn(ALOAD, 0);
mv.visitInsn(DUP);
mv.visitFieldInsn(GETFIELD, proxyName, HANDLERS_NAME, HANDLERS_DESCRIPTOR);
pushInteger(mv, methodIndex);
mv.visitInsn(AALOAD);
mv.visitInsn(SWAP);
// we don't use the method argument in InterceptorStackCallback.invoke, so can use null here
mv.visitInsn(ACONST_NULL);
packArguments(mv, method.getParameterTypes());
mv.visitMethodInsn(INVOKEINTERFACE, HANDLER_TYPE, "invoke", CALLBACK_DESCRIPTOR, true);
Class returnType = method.getReturnType();
if (returnType == void.class) {
mv.visitInsn(RETURN);
} else if (returnType.isPrimitive()) {
Type primitiveType = Type.getType(returnType);
unbox(mv, primitiveType);
mv.visitInsn(primitiveType.getOpcode(IRETURN));
} else {
mv.visitTypeInsn(CHECKCAST, Type.getInternalName(returnType));
mv.visitInsn(ARETURN);
}
mv.visitMaxs(0, 0);
mv.visitEnd();
}
@Override
protected void generateConstructorInvoker(MethodVisitor mv, Constructor constructor) {
String descriptor = Type.getConstructorDescriptor(constructor);
String enhancedDescriptor = '(' + HANDLERS_DESCRIPTOR + descriptor.substring(1);
mv.visitTypeInsn(NEW, proxyName);
mv.visitInsn(DUP);
mv.visitVarInsn(ALOAD, 1);
mv.visitTypeInsn(CHECKCAST, HANDLER_ARRAY_TYPE);
unpackArguments(mv, constructor.getParameterTypes());
mv.visitMethodInsn(INVOKESPECIAL, proxyName, "", enhancedDescriptor, false);
}
@Override
protected void generateMethodInvoker(MethodVisitor mv, Method method) {
Method target = bridgeDelegates.getOrDefault(method, method);
// if this was a bridge method and we know the target then replace superclass delegation
// with virtual dispatch to avoid skipping other interceptors overriding the target method
int invokeOpcode = target != method ? INVOKEVIRTUAL : INVOKESPECIAL;
mv.visitVarInsn(ALOAD, 1);
mv.visitTypeInsn(CHECKCAST, checkcastToProxy);
unpackArguments(mv, target.getParameterTypes());
mv.visitMethodInsn(
invokeOpcode, hostName, target.getName(), Type.getMethodDescriptor(target), false);
Class returnType = target.getReturnType();
if (returnType == void.class) {
mv.visitInsn(ACONST_NULL);
} else if (returnType.isPrimitive()) {
box(mv, Type.getType(returnType));
}
}
/** Override the original bridge method and replace it with virtual dispatch to the target. */
private void generateVirtualBridge(ClassWriter cw, Method bridge, Method target) {
MethodVisitor mv =
cw.visitMethod(
FINAL | (bridge.getModifiers() & ~(ABSTRACT | NATIVE | SYNCHRONIZED)),
bridge.getName(),
Type.getMethodDescriptor(bridge),
null,
exceptionNames(bridge));
mv.visitVarInsn(ALOAD, 0);
mv.visitTypeInsn(CHECKCAST, checkcastToProxy);
Class[] bridgeParameterTypes = bridge.getParameterTypes();
Class[] targetParameterTypes = target.getParameterTypes();
int slot = 1;
for (int i = 0, len = targetParameterTypes.length; i < len; i++) {
Class parameterType = targetParameterTypes[i];
slot += loadArgument(mv, parameterType, slot);
if (parameterType != bridgeParameterTypes[i]) {
// cast incoming argument to the specific type expected by target
mv.visitTypeInsn(CHECKCAST, Type.getInternalName(parameterType));
}
}
mv.visitMethodInsn(
INVOKEVIRTUAL, hostName, target.getName(), Type.getMethodDescriptor(target), false);
Type returnType = Type.getType(bridge.getReturnType());
if (target.getReturnType() != bridge.getReturnType()) {
// cast return value to the specific type expected by bridge
mv.visitTypeInsn(CHECKCAST, returnType.getInternalName());
}
mv.visitInsn(returnType.getOpcode(IRETURN));
mv.visitMaxs(0, 0);
mv.visitEnd();
}
@Override
protected MethodHandle lookupInvokerTable(Class glueClass) throws Throwable {
return (MethodHandle) glueClass.getField(INVOKERS_NAME).get(null);
}
/** Returns internal names of exceptions declared by the given constructor/method. */
private static String[] exceptionNames(Executable member) {
Class[] exceptionClasses = member.getExceptionTypes();
String[] exceptionNames = new String[exceptionClasses.length];
Arrays.setAll(exceptionNames, i -> Type.getInternalName(exceptionClasses[i]));
return exceptionNames;
}
}