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Byte Buddy is a Java library for creating Java classes at run time.
This artifact is a build of Byte Buddy with all ASM dependencies repackaged into its own name space.
/*
* Copyright 2014 - Present Rafael Winterhalter
*
* 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 net.bytebuddy.dynamic.loading;
import net.bytebuddy.agent.builder.AgentBuilder;
import net.bytebuddy.build.AccessControllerPlugin;
import net.bytebuddy.build.HashCodeAndEqualsPlugin;
import net.bytebuddy.description.type.TypeDescription;
import net.bytebuddy.dynamic.ClassFileLocator;
import net.bytebuddy.utility.JavaModule;
import net.bytebuddy.utility.dispatcher.JavaDispatcher;
import net.bytebuddy.utility.nullability.AlwaysNull;
import net.bytebuddy.utility.nullability.MaybeNull;
import java.io.File;
import java.io.IOException;
import java.lang.instrument.ClassDefinition;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.Instrumentation;
import java.lang.instrument.UnmodifiableClassException;
import java.security.PrivilegedAction;
import java.security.ProtectionDomain;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
/**
*
* The class reloading strategy allows to redefine loaded {@link java.lang.Class}es. Note that this strategy
* will always attempt to load an existing class prior to its redefinition, even if this class is not yet loaded.
*
*
* Note: In order to redefine any type, neither its name or its modifiers must be changed. Furthermore, no
* fields or methods must be removed or added. This makes this strategy generally incompatible to applying it to a
* rebased class definition as by {@link net.bytebuddy.ByteBuddy#rebase(Class)} which copies the original method
* implementations to additional methods. Furthermore, even the {@link net.bytebuddy.ByteBuddy#redefine(Class)}
* adds a method if the original class contains an explicit class initializer. For these reasons, it is not
* recommended to use this {@link ClassLoadingStrategy} with arbitrary classes.
*
*/
@HashCodeAndEqualsPlugin.Enhance
public class ClassReloadingStrategy implements ClassLoadingStrategy {
/**
* A dispatcher to use with some methods of the {@link Instrumentation} API.
*/
protected static final Dispatcher DISPATCHER = doPrivileged(JavaDispatcher.of(Dispatcher.class));
/**
* This instance's instrumentation.
*/
private final Instrumentation instrumentation;
/**
* An strategy which performs the actual redefinition of a {@link java.lang.Class}.
*/
private final Strategy strategy;
/**
* The strategy to apply for injecting classes into the bootstrap class loader.
*/
private final BootstrapInjection bootstrapInjection;
/**
* The preregistered types of this instance.
*/
private final Map> preregisteredTypes;
/**
* Creates a class reloading strategy for the given instrumentation using an explicit transformation strategy which
* is represented by an {@link Strategy}. The given instrumentation
* must support the strategy's transformation type.
*
* @param instrumentation The instrumentation to be used by this reloading strategy.
* @param strategy A strategy which performs the actual redefinition of a {@link java.lang.Class}.
*/
public ClassReloadingStrategy(Instrumentation instrumentation, Strategy strategy) {
this(instrumentation,
strategy,
BootstrapInjection.Disabled.INSTANCE,
Collections.>emptyMap());
}
/**
* Creates a new class reloading strategy.
*
* @param instrumentation The instrumentation to be used by this reloading strategy.
* @param strategy An strategy which performs the actual redefinition of a {@link java.lang.Class}.
* @param bootstrapInjection The bootstrap class loader injection strategy to use.
* @param preregisteredTypes The preregistered types of this instance.
*/
protected ClassReloadingStrategy(Instrumentation instrumentation,
Strategy strategy,
BootstrapInjection bootstrapInjection,
Map> preregisteredTypes) {
this.instrumentation = instrumentation;
this.strategy = strategy.validate(instrumentation);
this.bootstrapInjection = bootstrapInjection;
this.preregisteredTypes = preregisteredTypes;
}
/**
* A proxy for {@code java.security.AccessController#doPrivileged} that is activated if available.
*
* @param action The action to execute from a privileged context.
* @param The type of the action's resolved value.
* @return The action's resolved value.
*/
@AccessControllerPlugin.Enhance
private static T doPrivileged(PrivilegedAction action) {
return action.run();
}
/**
* Creates a class reloading strategy for the given instrumentation. The given instrumentation must either
* support {@link java.lang.instrument.Instrumentation#isRedefineClassesSupported()} or
* {@link java.lang.instrument.Instrumentation#isRetransformClassesSupported()}. If both modes are supported,
* classes will be transformed using a class retransformation.
*
* @param instrumentation The instrumentation to be used by this reloading strategy.
* @return A suitable class reloading strategy.
*/
public static ClassReloadingStrategy of(Instrumentation instrumentation) {
if (DISPATCHER.isRetransformClassesSupported(instrumentation)) {
return new ClassReloadingStrategy(instrumentation, Strategy.RETRANSFORMATION);
} else if (instrumentation.isRedefineClassesSupported()) {
return new ClassReloadingStrategy(instrumentation, Strategy.REDEFINITION);
} else {
throw new IllegalArgumentException("Instrumentation does not support reloading of classes: " + instrumentation);
}
}
/**
* Resolves the instrumentation provided by {@code net.bytebuddy.agent.Installer}.
*
* @return The installed instrumentation instance.
*/
private static Instrumentation resolveByteBuddyAgentInstrumentation() {
try {
Class installer = ClassLoader.getSystemClassLoader().loadClass("net.bytebuddy.agent.Installer");
JavaModule source = JavaModule.ofType(AgentBuilder.class), target = JavaModule.ofType(installer);
if (source != null && !source.canRead(target)) {
Class module = Class.forName("java.lang.Module");
module.getMethod("addReads", module).invoke(source.unwrap(), target.unwrap());
}
return (Instrumentation) installer.getMethod("getInstrumentation").invoke(null);
} catch (RuntimeException exception) {
throw exception;
} catch (Exception exception) {
throw new IllegalStateException("The Byte Buddy agent is not installed or not accessible", exception);
}
}
/**
*
* Obtains a {@link net.bytebuddy.dynamic.loading.ClassReloadingStrategy} from an installed Byte Buddy agent. This
* agent must be installed either by adding the {@code byte-buddy-agent.jar} when starting up the JVM by
*
*
*
* java -javaagent:byte-buddy-agent.jar -jar app.jar
*
*
* or after the start up using the Attach API. A convenience installer for the OpenJDK is provided by the
* {@code ByteBuddyAgent} within the {@code byte-buddy-agent} module. The strategy is determined by the agent's support
* for redefinition where are retransformation is preferred over a redefinition.
*
* @return A class reloading strategy which uses the Byte Buddy agent's {@link java.lang.instrument.Instrumentation}.
*/
public static ClassReloadingStrategy fromInstalledAgent() {
return ClassReloadingStrategy.of(resolveByteBuddyAgentInstrumentation());
}
/**
*
* Obtains a {@link net.bytebuddy.dynamic.loading.ClassReloadingStrategy} from an installed Byte Buddy agent. This
* agent must be installed either by adding the {@code byte-buddy-agent.jar} when starting up the JVM by
*
*
*
* java -javaagent:byte-buddy-agent.jar -jar app.jar
*
*
* or after the start up using the Attach API. A convenience installer for the OpenJDK is provided by the
* {@code ByteBuddyAgent} within the {@code byte-buddy-agent} module.
*
* @param strategy The strategy to use.
* @return A class reloading strategy which uses the Byte Buddy agent's {@link java.lang.instrument.Instrumentation}.
*/
public static ClassReloadingStrategy fromInstalledAgent(Strategy strategy) {
return new ClassReloadingStrategy(resolveByteBuddyAgentInstrumentation(), strategy);
}
/**
* {@inheritDoc}
*/
public Map> load(@MaybeNull ClassLoader classLoader, Map types) {
Map> availableTypes = new HashMap>(preregisteredTypes);
for (Class type : instrumentation.getInitiatedClasses(classLoader)) {
availableTypes.put(TypeDescription.ForLoadedType.getName(type), type);
}
Map, ClassDefinition> classDefinitions = new ConcurrentHashMap, ClassDefinition>();
Map> loadedClasses = new HashMap>();
Map unloadedClasses = new LinkedHashMap();
for (Map.Entry entry : types.entrySet()) {
Class type = availableTypes.get(entry.getKey().getName());
if (type != null) {
classDefinitions.put(type, new ClassDefinition(type, entry.getValue()));
loadedClasses.put(entry.getKey(), type);
} else {
unloadedClasses.put(entry.getKey(), entry.getValue());
}
}
try {
strategy.apply(instrumentation, classDefinitions);
if (!unloadedClasses.isEmpty()) {
loadedClasses.putAll((classLoader == null
? bootstrapInjection.make(instrumentation)
: new ClassInjector.UsingReflection(classLoader)).inject(unloadedClasses));
}
} catch (ClassNotFoundException exception) {
throw new IllegalArgumentException("Could not locate classes for redefinition", exception);
} catch (UnmodifiableClassException exception) {
throw new IllegalStateException("Cannot redefine specified class", exception);
}
return loadedClasses;
}
/**
* Resets all classes to their original definition while using the first type's class loader as a class file locator.
*
* @param type The types to reset.
* @return This class reloading strategy.
* @throws IOException If a class file locator causes an IO exception.
*/
public ClassReloadingStrategy reset(Class... type) throws IOException {
return type.length == 0
? this
: reset(ClassFileLocator.ForClassLoader.of(type[0].getClassLoader()), type);
}
/**
* Resets all classes to their original definition.
*
* @param classFileLocator The class file locator to use.
* @param type The types to reset.
* @return This class reloading strategy.
* @throws IOException If a class file locator causes an IO exception.
*/
public ClassReloadingStrategy reset(ClassFileLocator classFileLocator, Class... type) throws IOException {
if (type.length > 0) {
try {
strategy.reset(instrumentation, classFileLocator, Arrays.asList(type));
} catch (ClassNotFoundException exception) {
throw new IllegalArgumentException("Cannot locate types " + Arrays.toString(type), exception);
} catch (UnmodifiableClassException exception) {
throw new IllegalStateException("Cannot reset types " + Arrays.toString(type), exception);
}
}
return this;
}
/**
* Enables bootstrap injection for this class reloading strategy.
*
* @param folder The folder to save jar files in that are appended to the bootstrap class path.
* @return A class reloading strategy with bootstrap injection enabled.
*/
public ClassReloadingStrategy enableBootstrapInjection(File folder) {
return new ClassReloadingStrategy(instrumentation, strategy, new BootstrapInjection.Enabled(folder), preregisteredTypes);
}
/**
* Registers a type to be explicitly available without explicit lookup.
*
* @param type The loaded types that are explicitly available.
* @return This class reloading strategy with the given types being explicitly available.
*/
public ClassReloadingStrategy preregistered(Class... type) {
Map> preregisteredTypes = new HashMap>(this.preregisteredTypes);
for (Class aType : type) {
preregisteredTypes.put(TypeDescription.ForLoadedType.getName(aType), aType);
}
return new ClassReloadingStrategy(instrumentation, strategy, bootstrapInjection, preregisteredTypes);
}
/**
* A dispatcher to interact with the instrumentation API.
*/
@JavaDispatcher.Proxied("java.lang.instrument.Instrumentation")
protected interface Dispatcher {
/**
* Invokes the {@code Instrumentation#isModifiableClass} method.
*
* @param instrumentation The instrumentation instance to invoke the method on.
* @param type The type to consider for modifiability.
* @return {@code true} if the supplied type can be modified.
*/
boolean isModifiableClass(Instrumentation instrumentation, Class type);
/**
* Invokes the {@code Instrumentation#isRetransformClassesSupported} method.
*
* @param instrumentation The instrumentation instance to invoke the method on.
* @return {@code true} if the supplied instrumentation instance supports retransformation.
*/
boolean isRetransformClassesSupported(Instrumentation instrumentation);
/**
* Registers a transformer.
*
* @param instrumentation The instrumentation instance to invoke the method on.
* @param classFileTransformer The class file transformer to register.
* @param canRetransform {@code true} if the class file transformer should be invoked upon a retransformation.
*/
void addTransformer(Instrumentation instrumentation, ClassFileTransformer classFileTransformer, boolean canRetransform);
/**
* Retransforms the supplied classes.
*
* @param instrumentation The instrumentation instance to invoke the method on.
* @param type The types to retransform.
* @throws UnmodifiableClassException If any of the supplied types are unmodifiable.
*/
void retransformClasses(Instrumentation instrumentation, Class[] type) throws UnmodifiableClassException;
}
/**
* A strategy which performs the actual redefinition of a {@link java.lang.Class}.
*/
public enum Strategy {
/**
*
* Redefines a class using {@link java.lang.instrument.Instrumentation#redefineClasses(java.lang.instrument.ClassDefinition...)}.
*
*
* This strategy can be more efficient. However, the redefinition strategy does not allow to reset VM anonymous classes (e.g.
* classes that represent lambda expressions).
*
*/
REDEFINITION(true) {
@Override
protected void apply(Instrumentation instrumentation, Map, ClassDefinition> classDefinitions)
throws UnmodifiableClassException, ClassNotFoundException {
instrumentation.redefineClasses(classDefinitions.values().toArray(new ClassDefinition[0]));
}
@Override
protected Strategy validate(Instrumentation instrumentation) {
if (!instrumentation.isRedefineClassesSupported()) {
throw new IllegalArgumentException("Does not support redefinition: " + instrumentation);
}
return this;
}
@Override
public void reset(Instrumentation instrumentation, ClassFileLocator classFileLocator, List> types)
throws IOException, UnmodifiableClassException, ClassNotFoundException {
Map, ClassDefinition> classDefinitions = new HashMap, ClassDefinition>(types.size());
for (Class type : types) {
classDefinitions.put(type, new ClassDefinition(type, classFileLocator.locate(TypeDescription.ForLoadedType.getName(type)).resolve()));
}
apply(instrumentation, classDefinitions);
}
},
/**
*
* Redefines a class using
* {@link java.lang.instrument.Instrumentation#retransformClasses(Class[])}. This requires synchronization on
* the {@link net.bytebuddy.dynamic.loading.ClassReloadingStrategy#instrumentation} object.
*
*
* This strategy can require more time to be applied but does not struggle to reset VM anonymous classes (e.g. classes
* that represent lambda expressions).
*
*/
RETRANSFORMATION(false) {
@Override
protected void apply(Instrumentation instrumentation, Map, ClassDefinition> classDefinitions) throws UnmodifiableClassException {
ClassRedefinitionTransformer classRedefinitionTransformer = new ClassRedefinitionTransformer(classDefinitions);
synchronized (this) {
DISPATCHER.addTransformer(instrumentation, classRedefinitionTransformer, REDEFINE_CLASSES);
try {
DISPATCHER.retransformClasses(instrumentation, classDefinitions.keySet().toArray(new Class[0]));
} finally {
instrumentation.removeTransformer(classRedefinitionTransformer);
}
}
classRedefinitionTransformer.assertTransformation();
}
@Override
protected Strategy validate(Instrumentation instrumentation) {
if (!DISPATCHER.isRetransformClassesSupported(instrumentation)) {
throw new IllegalArgumentException("Does not support retransformation: " + instrumentation);
}
return this;
}
@Override
public void reset(Instrumentation instrumentation, ClassFileLocator classFileLocator, List> types) throws UnmodifiableClassException, ClassNotFoundException {
for (Class type : types) {
if (!DISPATCHER.isModifiableClass(instrumentation, type)) {
throw new IllegalArgumentException("Cannot modify type: " + type);
}
}
DISPATCHER.addTransformer(instrumentation, ClassResettingTransformer.INSTANCE, REDEFINE_CLASSES);
try {
DISPATCHER.retransformClasses(instrumentation, types.toArray(new Class[0]));
} finally {
instrumentation.removeTransformer(ClassResettingTransformer.INSTANCE);
}
}
};
/**
* Indicates that a class is not redefined.
*/
@AlwaysNull
private static final byte[] NO_REDEFINITION = null;
/**
* Instructs a {@link java.lang.instrument.ClassFileTransformer} to redefine classes.
*/
private static final boolean REDEFINE_CLASSES = true;
/**
* {@code true} if the {@link Strategy#REDEFINITION} strategy
* is used.
*/
private final boolean redefinition;
/**
* Creates a new strategy.
*
* @param redefinition {@code true} if the {@link Strategy#REDEFINITION} strategy is used.
*/
Strategy(boolean redefinition) {
this.redefinition = redefinition;
}
/**
* Applies this strategy for the given arguments.
*
* @param instrumentation The instrumentation to be used for applying the redefinition.
* @param classDefinitions A mapping of the classes to be redefined to their redefinition.
* @throws UnmodifiableClassException If a class is not modifiable.
* @throws ClassNotFoundException If a class was not found.
*/
protected abstract void apply(Instrumentation instrumentation, Map, ClassDefinition> classDefinitions)
throws UnmodifiableClassException, ClassNotFoundException;
/**
* Validates that this strategy supports a given transformation type.
*
* @param instrumentation The instrumentation instance being used.
* @return This strategy.
*/
protected abstract Strategy validate(Instrumentation instrumentation);
/**
* Returns {@code true} if this strategy represents {@link Strategy#REDEFINITION}.
*
* @return {@code true} if this strategy represents {@link Strategy#REDEFINITION}.
*/
public boolean isRedefinition() {
return redefinition;
}
/**
* Resets the provided types to their original format.
*
* @param instrumentation The instrumentation instance to use for class redefinition or retransformation.
* @param classFileLocator The class file locator to use.
* @param types The types to reset.
* @throws IOException If an I/O exception occurs.
* @throws UnmodifiableClassException If a class is not modifiable.
* @throws ClassNotFoundException If a class could not be found.
*/
public abstract void reset(Instrumentation instrumentation, ClassFileLocator classFileLocator, List> types) throws IOException, UnmodifiableClassException, ClassNotFoundException;
/**
* A class file transformer that applies a given {@link java.lang.instrument.ClassDefinition}.
*/
protected static class ClassRedefinitionTransformer implements ClassFileTransformer {
/**
* A mapping of classes to be redefined to their redefined class definitions.
*/
private final Map, ClassDefinition> redefinedClasses;
/**
* Creates a new class redefinition transformer.
*
* @param redefinedClasses A mapping of classes to be redefined to their redefined class definitions.
*/
protected ClassRedefinitionTransformer(Map, ClassDefinition> redefinedClasses) {
this.redefinedClasses = redefinedClasses;
}
/**
* {@inheritDoc}
*/
@MaybeNull
public byte[] transform(@MaybeNull ClassLoader classLoader,
@MaybeNull String internalTypeName,
@MaybeNull Class classBeingRedefined,
@MaybeNull ProtectionDomain protectionDomain,
byte[] classfileBuffer) {
if (internalTypeName == null) {
return NO_REDEFINITION;
}
ClassDefinition redefinedClass = redefinedClasses.remove(classBeingRedefined);
return redefinedClass == null
? NO_REDEFINITION
: redefinedClass.getDefinitionClassFile();
}
/**
* Validates that all given classes were redefined.
*/
public void assertTransformation() {
if (!redefinedClasses.isEmpty()) {
throw new IllegalStateException("Could not transform: " + redefinedClasses.keySet());
}
}
}
/**
* A transformer that indicates that a class file should not be transformed.
*/
protected enum ClassResettingTransformer implements ClassFileTransformer {
/**
* The singleton instance.
*/
INSTANCE;
/**
* {@inheritDoc}
*/
@MaybeNull
public byte[] transform(@MaybeNull ClassLoader classLoader,
@MaybeNull String internalTypeName,
@MaybeNull Class classBeingRedefined,
@MaybeNull ProtectionDomain protectionDomain,
byte[] classfileBuffer) {
return NO_REDEFINITION;
}
}
}
/**
* A strategy to apply for injecting classes into the bootstrap class loader.
*/
protected interface BootstrapInjection {
/**
* Creates a class injector to use.
*
* @param instrumentation The instrumentation of this instance.
* @return A class injector for the bootstrap class loader.
*/
ClassInjector make(Instrumentation instrumentation);
/**
* A disabled bootstrap injection strategy.
*/
enum Disabled implements BootstrapInjection {
/**
* The singleton instance.
*/
INSTANCE;
/**
* {@inheritDoc}
*/
public ClassInjector make(Instrumentation instrumentation) {
throw new IllegalStateException("Bootstrap injection is not enabled");
}
}
/**
* An enabled bootstrap class loader injection strategy.
*/
@HashCodeAndEqualsPlugin.Enhance
class Enabled implements BootstrapInjection {
/**
* The folder to save jar files in.
*/
private final File folder;
/**
* Creates an enabled bootstrap class injection strategy.
*
* @param folder The folder to save jar files in.
*/
protected Enabled(File folder) {
this.folder = folder;
}
/**
* {@inheritDoc}
*/
public ClassInjector make(Instrumentation instrumentation) {
return ClassInjector.UsingInstrumentation.of(folder, ClassInjector.UsingInstrumentation.Target.BOOTSTRAP, instrumentation);
}
}
}
}