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.implementation.bind.annotation;

import net.bytebuddy.build.HashCodeAndEqualsPlugin;
import net.bytebuddy.description.annotation.AnnotationDescription;
import net.bytebuddy.description.method.MethodDescription;
import net.bytebuddy.description.method.MethodList;
import net.bytebuddy.description.method.ParameterDescription;
import net.bytebuddy.description.type.TypeDescription;
import net.bytebuddy.dynamic.TargetType;
import net.bytebuddy.implementation.Implementation;
import net.bytebuddy.implementation.MethodAccessorFactory;
import net.bytebuddy.implementation.bind.MethodDelegationBinder;
import net.bytebuddy.implementation.bytecode.StackManipulation;
import net.bytebuddy.implementation.bytecode.assign.Assigner;
import net.bytebuddy.implementation.bytecode.constant.MethodConstant;
import net.bytebuddy.implementation.bytecode.constant.NullConstant;
import net.bytebuddy.implementation.bytecode.member.FieldAccess;
import org.objectweb.asm.MethodVisitor;

import java.lang.annotation.*;
import java.lang.reflect.Method;

import static net.bytebuddy.matcher.ElementMatchers.named;


A parameter with this annotation is assigned an instance of Method which invokes a default method implementation of this method. If such a method is not available, this annotation causes that this delegation target cannot be bound unless nullIfImpossible() is set to true. The method is declared as public and is invokable unless the instrumented type itself is not visible. Note that requesting such a method exposes the super method to reflection. 
See Also:
/**
 * A parameter with this annotation is assigned an instance of {@link Method} which invokes a default method implementation of this method.
 * If such a method is not available, this annotation causes that this delegation target cannot be bound unless {@link DefaultMethod#nullIfImpossible()}
 * is set to {@code true}. The method is declared as {@code public} and is invokable unless the instrumented type itself is not visible. Note that
 * requesting such a method exposes the super method to reflection.
 *
 * @see net.bytebuddy.implementation.MethodDelegation
 * @see net.bytebuddy.implementation.bind.annotation.TargetMethodAnnotationDrivenBinder
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.PARAMETER)
public @interface DefaultMethod {

    
Indicates if the instance assigned to this parameter should be stored in a static field for reuse.

Returns:true if this method instance should be cached.
/**
     * Indicates if the instance assigned to this parameter should be stored in a static field for reuse.
     *
     * @return {@code true} if this method instance should be cached.
     */
    boolean cached() default true;

    
Indicates if the instance assigned to this parameter should be looked up using an AccessController. 
Returns:true if this method should be looked up using an AccessController.
/**
     * Indicates if the instance assigned to this parameter should be looked up using an {@link java.security.AccessController}.
     *
     * @return {@code true} if this method should be looked up using an {@link java.security.AccessController}.
     */
    boolean privileged() default false;

    
Specifies an explicit type that declares the default method to invoke.

Returns:The type declaring the method to invoke or TargetType to indicate that the instrumented method declared the method.
/**
     * Specifies an explicit type that declares the default method to invoke.
     *
     * @return The type declaring the method to invoke or {@link TargetType} to indicate that the instrumented method declared the method.
     */
    Class<?> targetType() default void.class;

    
Indicates that null should be assigned to this parameter if no default method is invokable. 
Returns:true if null should be assigned if no valid method can be assigned.
/**
     * Indicates that {@code null} should be assigned to this parameter if no default method is invokable.
     *
     * @return {@code true} if {@code null} should be assigned if no valid method can be assigned.
     */
    boolean nullIfImpossible() default false;

    
A binder for the DefaultMethod annotation. 
/**
     * A binder for the {@link DefaultMethod} annotation.
     */
    enum Binder implements TargetMethodAnnotationDrivenBinder.ParameterBinder<DefaultMethod> {

        
The singleton instance.

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

        
The DefaultMethod.cached() property. 
/**
         * The {@link DefaultMethod#cached()} property.
         */
        private static final MethodDescription.InDefinedShape CACHED;

        /**
         * The {@link DefaultMethod#privileged()} property.
         */
        private static final MethodDescription.InDefinedShape PRIVILEGED;

        /**
         * The {@link DefaultMethod#targetType()} property.
         */
        private static final MethodDescription.InDefinedShape TARGET_TYPE;

        /**
         * The {@link DefaultMethod#nullIfImpossible()} property.
         */
        private static final MethodDescription.InDefinedShape NULL_IF_IMPOSSIBLE;

        /*
         * Locates method constants for properties of the default method annotation.
         */
        static {
            MethodList<MethodDescription.InDefinedShape> methodList = TypeDescription.ForLoadedType.of(DefaultMethod.class).getDeclaredMethods();
            CACHED = methodList.filter(named("cached")).getOnly();
            PRIVILEGED = methodList.filter(named("privileged")).getOnly();
            TARGET_TYPE = methodList.filter(named("targetType")).getOnly();
            NULL_IF_IMPOSSIBLE = methodList.filter(named("nullIfImpossible")).getOnly();
        }

        
{@inheritDoc}

/**
         * {@inheritDoc}
         */
        public Class<DefaultMethod> getHandledType() {
            return DefaultMethod.class;
        }

        
{@inheritDoc}

/**
         * {@inheritDoc}
         */
        public MethodDelegationBinder.ParameterBinding<?> bind(final AnnotationDescription.Loadable<DefaultMethod> annotation,
                                                               MethodDescription source,
                                                               ParameterDescription target,
                                                               Implementation.Target implementationTarget,
                                                               Assigner assigner,
                                                               Assigner.Typing typing) {
            if (!target.getType().asErasure().isAssignableFrom(Method.class)) {
                throw new IllegalStateException("Cannot assign Method type to " + target);
            } else if (source.isMethod()) {
                TypeDescription typeDescription = annotation.getValue(TARGET_TYPE).resolve(TypeDescription.class);
                Implementation.SpecialMethodInvocation specialMethodInvocation = (typeDescription.represents(void.class)
                        ? MethodLocator.ForImplicitType.INSTANCE
                        : new MethodLocator.ForExplicitType(typeDescription)).resolve(implementationTarget, source).withCheckedCompatibilityTo(source.asTypeToken());
                if (specialMethodInvocation.isValid()) {
                    return new MethodDelegationBinder.ParameterBinding.Anonymous(new DelegationMethod(specialMethodInvocation,
                            annotation.getValue(CACHED).resolve(Boolean.class),
                            annotation.getValue(PRIVILEGED).resolve(Boolean.class)));
                } else if (annotation.getValue(NULL_IF_IMPOSSIBLE).resolve(Boolean.class)) {
                    return new MethodDelegationBinder.ParameterBinding.Anonymous(NullConstant.INSTANCE);
                } else {
                    return MethodDelegationBinder.ParameterBinding.Illegal.INSTANCE;
                }
            } else if (annotation.getValue(NULL_IF_IMPOSSIBLE).resolve(Boolean.class)) {
                return new MethodDelegationBinder.ParameterBinding.Anonymous(NullConstant.INSTANCE);
            } else {
                return MethodDelegationBinder.ParameterBinding.Illegal.INSTANCE;
            }
        }

        
A method locator is responsible for creating the super method call.

/**
         * A method locator is responsible for creating the super method call.
         */
        protected interface MethodLocator {

            
Resolves the special method invocation to this target.

Params:
  • implementationTarget – The implementation target.
  • source –               The method being instrumented.
Returns:A special method invocation that represents the super call of this binding.
/**
             * Resolves the special method invocation to this target.
             *
             * @param implementationTarget The implementation target.
             * @param source               The method being instrumented.
             * @return A special method invocation that represents the super call of this binding.
             */
            Implementation.SpecialMethodInvocation resolve(Implementation.Target implementationTarget, MethodDescription source);

            
A method locator for an implicit target type.

/**
             * A method locator for an implicit target type.
             */
            enum ForImplicitType implements MethodLocator {

                
The singleton instance.

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

                
{@inheritDoc}

/**
                 * {@inheritDoc}
                 */
                public Implementation.SpecialMethodInvocation resolve(Implementation.Target implementationTarget, MethodDescription source) {
                    return implementationTarget.invokeDefault(source.asSignatureToken());
                }
            }

            
A method locator for an explicit target type.

/**
             * A method locator for an explicit target type.
             */
            @HashCodeAndEqualsPlugin.Enhance
            class ForExplicitType implements MethodLocator {

                
The explicit target type.

/**
                 * The explicit target type.
                 */
                private final TypeDescription typeDescription;

                
Creates a method locator for an explicit target.

Params:
  • typeDescription – The explicit target type.
/**
                 * Creates a method locator for an explicit target.
                 *
                 * @param typeDescription The explicit target type.
                 */
                protected ForExplicitType(TypeDescription typeDescription) {
                    this.typeDescription = typeDescription;
                }

                
{@inheritDoc}

/**
                 * {@inheritDoc}
                 */
                public Implementation.SpecialMethodInvocation resolve(Implementation.Target implementationTarget, MethodDescription source) {
                    if (!typeDescription.isInterface()) {
                        throw new IllegalStateException(source + " method carries default method call parameter on non-interface type");
                    }
                    return implementationTarget.invokeDefault(source.asSignatureToken(), TargetType.resolve(typeDescription, implementationTarget.getInstrumentedType()));
                }
            }
        }

        
Loads the delegation method constant onto the stack.

/**
         * Loads the delegation method constant onto the stack.
         */
        @HashCodeAndEqualsPlugin.Enhance
        protected static class DelegationMethod implements StackManipulation {

            
The special method invocation that represents the super method call.

/**
             * The special method invocation that represents the super method call.
             */
            private final Implementation.SpecialMethodInvocation specialMethodInvocation;

            
true if the method constant should be cached. 
/**
             * {@code true} if the method constant should be cached.
             */
            private final boolean cached;

            
true if the method should be looked up using an AccessController. 
/**
             * {@code true} if the method should be looked up using an {@link java.security.AccessController}.
             */
            private final boolean privileged;

            
Creates a new delegation method.

Params:
  • specialMethodInvocation – The special method invocation that represents the super method call.
  • cached –  true if the method constant should be cached.
  • privileged –  true if the method should be looked up using an AccessController.
/**
             * Creates a new delegation method.
             *
             * @param specialMethodInvocation The special method invocation that represents the super method call.
             * @param cached                  {@code true} if the method constant should be cached.
             * @param privileged              {@code true} if the method should be looked up using an {@link java.security.AccessController}.
             */
            protected DelegationMethod(Implementation.SpecialMethodInvocation specialMethodInvocation, boolean cached, boolean privileged) {
                this.specialMethodInvocation = specialMethodInvocation;
                this.cached = cached;
                this.privileged = privileged;
            }

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            public boolean isValid() {
                return specialMethodInvocation.isValid();
            }

            
{@inheritDoc}

/**
             * {@inheritDoc}
             */
            public Size apply(MethodVisitor methodVisitor, Implementation.Context implementationContext) {
                StackManipulation methodConstant = privileged
                        ? MethodConstant.ofPrivileged(implementationContext.registerAccessorFor(specialMethodInvocation, MethodAccessorFactory.AccessType.PUBLIC))
                        : MethodConstant.of(implementationContext.registerAccessorFor(specialMethodInvocation, MethodAccessorFactory.AccessType.PUBLIC));
                return (cached
                        ? FieldAccess.forField(implementationContext.cache(methodConstant, TypeDescription.ForLoadedType.of(Method.class))).read()
                        : methodConstant).apply(methodVisitor, implementationContext);
            }
        }
    }
}