https://bytebuddy.net/byte-buddy-dep: Byte Buddy is a Java library for creating Java classes at run time. This artifact is a build of Byte Buddy with a remaining dependency onto ASM. You should never depend on this module without repackaging Byte Buddy and ASM into your own namespace. 
/*
 * Copyright 2014 - 2020 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 edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
import net.bytebuddy.build.HashCodeAndEqualsPlugin;
import net.bytebuddy.description.type.TypeDescription;
import net.bytebuddy.dynamic.ClassFileLocator;

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.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.ProtectionDomain;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;


 The class reloading strategy allows to redefine loaded Classes. 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 ByteBuddy.rebase(Class<Object>) which copies the original method implementations to additional methods. Furthermore, even the ByteBuddy.redefine(Class<Object>) adds a method if the original class contains an explicit class initializer. For these reasons, it is not recommended to use this ClassLoadingStrategy with arbitrary classes. 


/**
 * <p>
 * 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.
 * </p>
 * <p>
 * <b>Note</b>: 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 <i>class initializer</i>. For these reasons, it is not
 * recommended to use this {@link ClassLoadingStrategy} with arbitrary classes.
 * </p>
 */
@HashCodeAndEqualsPlugin.Enhance
public class ClassReloadingStrategy implements ClassLoadingStrategy<ClassLoader> {

    
The name of the Byte Buddy net.bytebuddy.agent.Installer class. 
/**
     * The name of the Byte Buddy {@code net.bytebuddy.agent.Installer} class.
     */
    private static final String INSTALLER_TYPE = "net.bytebuddy.agent.Installer";

    
The name of the net.bytebuddy.agent.Installer getter for reading an installed Instrumentation. 
/**
     * The name of the {@code net.bytebuddy.agent.Installer} getter for reading an installed {@link Instrumentation}.
     */
    private static final String INSTRUMENTATION_GETTER = "getInstrumentation";

    
Indicator for access to a static member via reflection to make the code more readable.

/**
     * Indicator for access to a static member via reflection to make the code more readable.
     */
    private static final Object STATIC_MEMBER = null;

    
A dispatcher to use with some methods of the Instrumentation API. 
/**
     * A dispatcher to use with some methods of the {@link Instrumentation} API.
     */
    protected static final Dispatcher DISPATCHER = AccessController.doPrivileged(Dispatcher.CreationAction.INSTANCE);

    
This instance's instrumentation.

/**
     * This instance's instrumentation.
     */
    private final Instrumentation instrumentation;

    
An strategy which performs the actual redefinition of a Class. 
/**
     * 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.

/**
     * The strategy to apply for injecting classes into the bootstrap class loader.
     */
    private final BootstrapInjection bootstrapInjection;

    
The preregistered types of this instance.

/**
     * The preregistered types of this instance.
     */
    private final Map<String, Class<?>> preregisteredTypes;

    
Creates a class reloading strategy for the given instrumentation using an explicit transformation strategy which is represented by an Strategy. The given instrumentation must support the strategy's transformation type. 
Params:
  • instrumentation – The instrumentation to be used by this reloading strategy.
  • strategy –  A strategy which performs the actual redefinition of a Class.
/**
     * 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.<String, Class<?>>emptyMap());
    }

    
Creates a new class reloading strategy.

Params:
  • instrumentation –    The instrumentation to be used by this reloading strategy.
  • strategy –  An strategy which performs the actual redefinition of a Class.
  • bootstrapInjection – The bootstrap class loader injection strategy to use.
  • preregisteredTypes – The preregistered types of this instance.
/**
     * 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<String, Class<?>> preregisteredTypes) {
        this.instrumentation = instrumentation;
        this.strategy = strategy.validate(instrumentation);
        this.bootstrapInjection = bootstrapInjection;
        this.preregisteredTypes = preregisteredTypes;
    }

    
Creates a class reloading strategy for the given instrumentation. The given instrumentation must either support Instrumentation.isRedefineClassesSupported() or Instrumentation.isRetransformClassesSupported(). If both modes are supported, classes will be transformed using a class retransformation. 
Params:
  • instrumentation – The instrumentation to be used by this reloading strategy.
Returns:A suitable class reloading strategy.
/**
     * 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);
        }
    }

    
 Obtains a ClassReloadingStrategy from an installed Byte Buddy agent. This agent must be installed either by adding the 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 ByteBuddyAgent within the byte-buddy-agent module. The strategy is determined by the agent's support for redefinition where are retransformation is preferred over a redefinition. 
Returns:A class reloading strategy which uses the Byte Buddy agent's Instrumentation.
/**
     * <p>
     * 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
     * </p>
     * <p>
     * <code>
     * java -javaagent:byte-buddy-agent.jar -jar app.jar
     * </code>
     * </p>
     * 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() {
        try {
            return ClassReloadingStrategy.of((Instrumentation) ClassLoader.getSystemClassLoader()
                    .loadClass(INSTALLER_TYPE)
                    .getMethod(INSTRUMENTATION_GETTER)
                    .invoke(STATIC_MEMBER));
        } catch (RuntimeException exception) {
            throw exception;
        } catch (Exception exception) {
            throw new IllegalStateException("The Byte Buddy agent is not installed or not accessible", exception);
        }
    }

    
 Obtains a ClassReloadingStrategy from an installed Byte Buddy agent. This agent must be installed either by adding the 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 ByteBuddyAgent within the byte-buddy-agent module. 
Params:
  • strategy – The strategy to use.
Returns:A class reloading strategy which uses the Byte Buddy agent's Instrumentation.
/**
     * <p>
     * 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
     * </p>
     * <p>
     * <code>
     * java -javaagent:byte-buddy-agent.jar -jar app.jar
     * </code>
     * </p>
     * 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) {
        try {
            return new ClassReloadingStrategy((Instrumentation) ClassLoader.getSystemClassLoader()
                    .loadClass(INSTALLER_TYPE)
                    .getMethod(INSTRUMENTATION_GETTER)
                    .invoke(STATIC_MEMBER), strategy);
        } catch (RuntimeException exception) {
            throw exception;
        } catch (Exception exception) {
            throw new IllegalStateException("The Byte Buddy agent is not installed or not accessible", exception);
        }
    }

    
{@inheritDoc}

/**
     * {@inheritDoc}
     */
    public Map<TypeDescription, Class<?>> load(ClassLoader classLoader, Map<TypeDescription, byte[]> types) {
        Map<String, Class<?>> availableTypes = new HashMap<String, Class<?>>(preregisteredTypes);
        for (Class<?> type : instrumentation.getInitiatedClasses(classLoader)) {
            availableTypes.put(TypeDescription.ForLoadedType.getName(type), type);
        }
        Map<Class<?>, ClassDefinition> classDefinitions = new ConcurrentHashMap<Class<?>, ClassDefinition>();
        Map<TypeDescription, Class<?>> loadedClasses = new HashMap<TypeDescription, Class<?>>();
        Map<TypeDescription, byte[]> unloadedClasses = new LinkedHashMap<TypeDescription, byte[]>();
        for (Map.Entry<TypeDescription, byte[]> 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.

Params:
  • type – The types to reset.
Throws:
  • IOException – If a class file locator causes an IO exception.
Returns:This class reloading strategy.
/**
     * 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.

Params:
  • classFileLocator – The class file locator to use.
  • type –             The types to reset.
Throws:
  • IOException – If a class file locator causes an IO exception.
Returns:This class reloading strategy.
/**
     * 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.

Params:
  • folder – The folder to save jar files in that are appended to the bootstrap class path.
Returns:A class reloading strategy with bootstrap injection enabled.
/**
     * 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.

Params:
  • type – The loaded types that are explicitly available.
Returns:This class reloading strategy with the given types being explicitly available.
/**
     * 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<String, Class<?>> preregisteredTypes = new HashMap<String, Class<?>>(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.

/**
     * A dispatcher to interact with the instrumentation API.
     */
    protected interface Dispatcher {

        
Invokes the Instrumentation#isModifiableClass method. 
Params:
  • instrumentation – The instrumentation instance to invoke the method on.
  • type –            The type to consider for modifiability.
Returns:true if the supplied type can be modified.
/**
         * 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 Instrumentation#isRetransformClassesSupported method. 
Params:
  • instrumentation – The instrumentation instance to invoke the method on.
Returns:true if the supplied instrumentation instance supports retransformation.
/**
         * 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.

Params:
  • instrumentation –      The instrumentation instance to invoke the method on.
  • classFileTransformer – The class file transformer to register.
  • canRetransform –  true if the class file transformer should be invoked upon a retransformation.
/**
         * 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.

Params:
  • instrumentation – The instrumentation instance to invoke the method on.
  • type –            The types to retransform.
Throws:
/**
         * 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;

        
An action to create an appropriate Dispatcher. 
/**
         * An action to create an appropriate {@link Dispatcher}.
         */
        enum CreationAction implements PrivilegedAction<Dispatcher> {

            
The singleton instance.

/**
             * The singleton instance.
             */
            INSTANCE;

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            public Dispatcher run() {
                try {
                    Class<?> instrumentation = Class.forName("java.lang.instrument.Instrumentation");
                    return new ForJava6CapableVm(instrumentation.getMethod("isModifiableClass", Class.class),
                            instrumentation.getMethod("isRetransformClassesSupported"),
                            instrumentation.getMethod("addTransformer", ClassFileTransformer.class, boolean.class),
                            instrumentation.getMethod("retransformClasses", Class[].class));
                } catch (ClassNotFoundException ignored) {
                    return ForLegacyVm.INSTANCE;
                } catch (NoSuchMethodException ignored) {
                    return ForLegacyVm.INSTANCE;
                }
            }
        }

        
A dispatcher for a legacy VM that does not support retransformation.

/**
         * A dispatcher for a legacy VM that does not support retransformation.
         */
        enum ForLegacyVm implements Dispatcher {

            
The singleton instance.

/**
             * The singleton instance.
             */
            INSTANCE;

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            public boolean isModifiableClass(Instrumentation instrumentation, Class<?> type) {
                return !type.isArray() && !type.isPrimitive();
            }

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            public boolean isRetransformClassesSupported(Instrumentation instrumentation) {
                return false;
            }

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            public void addTransformer(Instrumentation instrumentation, ClassFileTransformer classFileTransformer, boolean canRetransform) {
                if (canRetransform) {
                    throw new UnsupportedOperationException("Cannot apply retransformation on legacy VM");
                } else {
                    instrumentation.addTransformer(classFileTransformer);
                }
            }

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            public void retransformClasses(Instrumentation instrumentation, Class<?>[] type) {
                throw new IllegalStateException();
            }
        }

        
A dispatcher for a Java 6 capable VM that is potentially capable of retransformation.

/**
         * A dispatcher for a Java 6 capable VM that is potentially capable of retransformation.
         */
        class ForJava6CapableVm implements Dispatcher {

            
The Instrumentation#isModifiableClass method. 
/**
             * The {@code Instrumentation#isModifiableClass} method.
             */
            private final Method isModifiableClass;

            
The Instrumentation#isRetransformClassesSupported method. 
/**
             * The {@code Instrumentation#isRetransformClassesSupported} method.
             */
            private final Method isRetransformClassesSupported;

            
The Instrumentation#addTransformer method. 
/**
             * The {@code Instrumentation#addTransformer} method.
             */
            private final Method addTransformer;

            
The Instrumentation#retransformClasses method. 
/**
             * The {@code Instrumentation#retransformClasses} method.
             */
            private final Method retransformClasses;

            
Creates a dispatcher for a Java 6 compatible VM.

Params:
  • isModifiableClass –  The Instrumentation#isModifiableClass method.
  • isRetransformClassesSupported – The Instrumentation#isRetransformClassesSupported method.
  • addTransformer –  The Instrumentation#addTransformer method.
  • retransformClasses –  The Instrumentation#retransformClasses method.
/**
             * Creates a dispatcher for a Java 6 compatible VM.
             *
             * @param isModifiableClass             The {@code Instrumentation#isModifiableClass} method.
             * @param isRetransformClassesSupported The {@code Instrumentation#isRetransformClassesSupported} method.
             * @param addTransformer                The {@code Instrumentation#addTransformer} method.
             * @param retransformClasses            The {@code Instrumentation#retransformClasses} method.
             */
            protected ForJava6CapableVm(Method isModifiableClass,
                                        Method isRetransformClassesSupported,
                                        Method addTransformer,
                                        Method retransformClasses) {
                this.isModifiableClass = isModifiableClass;
                this.isRetransformClassesSupported = isRetransformClassesSupported;
                this.addTransformer = addTransformer;
                this.retransformClasses = retransformClasses;
            }

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            public boolean isModifiableClass(Instrumentation instrumentation, Class<?> type) {
                try {
                    return (Boolean) isModifiableClass.invoke(instrumentation, type);
                } catch (IllegalAccessException exception) {
                    throw new IllegalStateException("Cannot access java.lang.instrument.Instrumentation#isModifiableClass", exception);
                } catch (InvocationTargetException exception) {
                    throw new IllegalStateException("Error invoking java.lang.instrument.Instrumentation#isModifiableClass", exception.getCause());
                }
            }

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            public boolean isRetransformClassesSupported(Instrumentation instrumentation) {
                try {
                    return (Boolean) isRetransformClassesSupported.invoke(instrumentation);
                } catch (IllegalAccessException exception) {
                    throw new IllegalStateException("Cannot access java.lang.instrument.Instrumentation#isModifiableClass", exception);
                } catch (InvocationTargetException exception) {
                    throw new IllegalStateException("Error invoking java.lang.instrument.Instrumentation#isModifiableClass", exception.getCause());
                }
            }

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            public void addTransformer(Instrumentation instrumentation, ClassFileTransformer classFileTransformer, boolean canRetransform) {
                try {
                    addTransformer.invoke(instrumentation, classFileTransformer, canRetransform);
                } catch (IllegalAccessException exception) {
                    throw new IllegalStateException("Cannot access java.lang.instrument.Instrumentation#addTransformer", exception);
                } catch (InvocationTargetException exception) {
                    throw new IllegalStateException("Error invoking java.lang.instrument.Instrumentation#addTransformer", exception.getCause());
                }
            }

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            public void retransformClasses(Instrumentation instrumentation, Class<?>[] type) throws UnmodifiableClassException {
                try {
                    retransformClasses.invoke(instrumentation, (Object) type);
                } catch (IllegalAccessException exception) {
                    throw new IllegalStateException("Cannot access java.lang.instrument.Instrumentation#retransformClasses", exception);
                } catch (InvocationTargetException exception) {
                    Throwable cause = exception.getCause();
                    if (cause instanceof UnmodifiableClassException) {
                        throw (UnmodifiableClassException) cause;
                    } else {
                        throw new IllegalStateException("Error invoking java.lang.instrument.Instrumentation#retransformClasses", cause);
                    }
                }
            }
        }
    }

    
A strategy which performs the actual redefinition of a Class. 
/**
     * A strategy which performs the actual redefinition of a {@link java.lang.Class}.
     */
    public enum Strategy {

        
 Redefines a class using Instrumentation.redefineClasses(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).



/**
         * <p>
         * Redefines a class using {@link java.lang.instrument.Instrumentation#redefineClasses(java.lang.instrument.ClassDefinition...)}.
         * </p>
         * <p>
         * 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).
         * </p>
         */
        REDEFINITION(true) {
            @Override
            protected void apply(Instrumentation instrumentation, Map<Class<?>, 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<Class<?>> types)
                    throws IOException, UnmodifiableClassException, ClassNotFoundException {
                Map<Class<?>, ClassDefinition> classDefinitions = new HashMap<Class<?>, 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 Instrumentation.retransformClasses(Class<?>[]). This requires synchronization on the 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).



/**
         * <p>
         * Redefines a class using
         * {@link java.lang.instrument.Instrumentation#retransformClasses(Class[])}. This requires synchronization on
         * the {@link net.bytebuddy.dynamic.loading.ClassReloadingStrategy#instrumentation} object.
         * </p>
         * <p>
         * 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).
         * </p>
         */
        RETRANSFORMATION(false) {
            @Override
            protected void apply(Instrumentation instrumentation, Map<Class<?>, 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<Class<?>> 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.

/**
         * Indicates that a class is not redefined.
         */
        private static final byte[] NO_REDEFINITION = null;

        
Instructs a ClassFileTransformer to redefine classes. 
/**
         * Instructs a {@link java.lang.instrument.ClassFileTransformer} to redefine classes.
         */
        private static final boolean REDEFINE_CLASSES = true;

        
true if the REDEFINITION strategy is used. 
/**
         * {@code true} if the {@link Strategy#REDEFINITION} strategy
         * is used.
         */
        private final boolean redefinition;

        
Creates a new strategy.

Params:
/**
         * 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.

Params:
  • instrumentation –  The instrumentation to be used for applying the redefinition.
  • classDefinitions – A mapping of the classes to be redefined to their redefinition.
Throws:
/**
         * 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<Class<?>, ClassDefinition> classDefinitions)
                throws UnmodifiableClassException, ClassNotFoundException;

        
Validates that this strategy supports a given transformation type.

Params:
  • instrumentation – The instrumentation instance being used.
Returns:This strategy.
/**
         * 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 true if this strategy represents REDEFINITION. 
Returns:true if this strategy represents REDEFINITION.
/**
         * 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.

Params:
  • instrumentation –  The instrumentation instance to use for class redefinition or retransformation.
  • classFileLocator – The class file locator to use.
  • types –            The types to reset.
Throws:
/**
         * 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<Class<?>> types) throws IOException, UnmodifiableClassException, ClassNotFoundException;

        
A class file transformer that applies a given ClassDefinition. 
/**
         * 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.

/**
             * A mapping of classes to be redefined to their redefined class definitions.
             */
            private final Map<Class<?>, ClassDefinition> redefinedClasses;

            
Creates a new class redefinition transformer.

Params:
  • redefinedClasses – A mapping of classes to be redefined to their redefined class definitions.
/**
             * Creates a new class redefinition transformer.
             *
             * @param redefinedClasses A mapping of classes to be redefined to their redefined class definitions.
             */
            protected ClassRedefinitionTransformer(Map<Class<?>, ClassDefinition> redefinedClasses) {
                this.redefinedClasses = redefinedClasses;
            }

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            @SuppressFBWarnings(value = "EI_EXPOSE_REP", justification = "Value is always null")
            public byte[] transform(ClassLoader classLoader,
                                    String internalTypeName,
                                    Class<?> classBeingRedefined,
                                    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.

/**
             * 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.

/**
         * A transformer that indicates that a class file should not be transformed.
         */
        protected enum ClassResettingTransformer implements ClassFileTransformer {

            
The singleton instance.

/**
             * The singleton instance.
             */
            INSTANCE;

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            public byte[] transform(ClassLoader classLoader,
                                    String internalTypeName,
                                    Class<?> classBeingRedefined,
                                    ProtectionDomain protectionDomain,
                                    byte[] classfileBuffer) {
                return NO_REDEFINITION;
            }
        }
    }

    
A strategy to apply for injecting classes into the bootstrap class loader.

/**
     * A strategy to apply for injecting classes into the bootstrap class loader.
     */
    protected interface BootstrapInjection {

        
Creates a class injector to use.

Params:
  • instrumentation – The instrumentation of this instance.
Returns:A class injector for the bootstrap class loader.
/**
         * 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.

/**
         * A disabled bootstrap injection strategy.
         */
        enum Disabled implements BootstrapInjection {

            
The singleton instance.

/**
             * The singleton instance.
             */
            INSTANCE;

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            public ClassInjector make(Instrumentation instrumentation) {
                throw new IllegalStateException("Bootstrap injection is not enabled");
            }
        }

        
An enabled bootstrap class loader injection strategy.

/**
         * An enabled bootstrap class loader injection strategy.
         */
        @HashCodeAndEqualsPlugin.Enhance
        class Enabled implements BootstrapInjection {

            
The folder to save jar files in.

/**
             * The folder to save jar files in.
             */
            private final File folder;

            
Creates an enabled bootstrap class injection strategy.

Params:
  • folder – The folder to save jar files in.
/**
             * Creates an enabled bootstrap class injection strategy.
             *
             * @param folder The folder to save jar files in.
             */
            protected Enabled(File folder) {
                this.folder = folder;
            }

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            public ClassInjector make(Instrumentation instrumentation) {
                return ClassInjector.UsingInstrumentation.of(folder, ClassInjector.UsingInstrumentation.Target.BOOTSTRAP, instrumentation);
            }
        }
    }
}