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.implementation.Implementation;
import net.bytebuddy.implementation.auxiliary.MethodCallProxy;
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.NullConstant;

import java.lang.annotation.*;
import java.util.concurrent.Callable;

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


A parameter with this annotation is assigned a proxy for invoking a default method that fits the intercepted method.
If no suitable default method for the intercepted method can be identified, the target method with the annotated
parameter is considered to be unbindable.

See Also:
/**
 * A parameter with this annotation is assigned a proxy for invoking a default method that fits the intercepted method.
 * If no suitable default method for the intercepted method can be identified, the target method with the annotated
 * parameter is considered to be unbindable.
 *
 * @see net.bytebuddy.implementation.MethodDelegation
 * @see net.bytebuddy.implementation.bind.annotation.TargetMethodAnnotationDrivenBinder
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.PARAMETER)
public @interface DefaultCall {

    
If this parameter is not explicitly set, a parameter with the DefaultCall is only bound to a source method if this source method directly represents an unambiguous, invokable default method. On the other hand, if a method is not defined unambiguously by an interface, not setting this parameter will exclude the target method with the annotated parameter from a binding to the source method. 
 

If this parameter is however set to an explicit interface type, a default method is always invoked on this given
type as long as this type defines a method with a compatible signature. If this is not the case, the target
method with the annotated parameter is not longer considered as a possible binding candidate of a source method.

Returns:The target interface that a default method invocation is to be defined upon. If no such explicit target is set, this parameter should not be defined as the predefined void type encodes an implicit resolution.
/**
     * If this parameter is not explicitly set, a parameter with the
     * {@link net.bytebuddy.implementation.bind.annotation.DefaultCall} is only bound to a
     * source method if this source method directly represents an unambiguous, invokable default method. On the other
     * hand, if a method is not defined unambiguously by an interface, not setting this parameter will exclude
     * the target method with the annotated parameter from a binding to the source method.
     * <p>&nbsp;</p>
     * If this parameter is however set to an explicit interface type, a default method is always invoked on this given
     * type as long as this type defines a method with a compatible signature. If this is not the case, the target
     * method with the annotated parameter is not longer considered as a possible binding candidate of a source method.
     *
     * @return The target interface that a default method invocation is to be defined upon. If no such explicit target
     * is set, this parameter should not be defined as the predefined {@code void} type encodes an implicit resolution.
     */
    Class<?> targetType() default void.class;

    
Determines if the generated proxy should be Serializable. 
Returns:true if the generated proxy should be Serializable.
/**
     * Determines if the generated proxy should be {@link java.io.Serializable}.
     *
     * @return {@code true} if the generated proxy should be {@link java.io.Serializable}.
     */
    boolean serializableProxy() default false;

    
Assigns null to the parameter if it is impossible to invoke the super method or a possible dominant default method, if permitted. 
Returns:true if a null constant should be assigned to this parameter in case that a legal binding is impossible.
/**
     * Assigns {@code null} to the parameter if it is impossible to invoke the super method or a possible dominant default method, if permitted.
     *
     * @return {@code true} if a {@code null} constant should be assigned to this parameter in case that a legal binding is impossible.
     */
    boolean nullIfImpossible() default false;

    
A binder for handling the DefaultCall annotation. 
See Also:
/**
     * A binder for handling the
     * {@link net.bytebuddy.implementation.bind.annotation.DefaultCall}
     * annotation.
     *
     * @see TargetMethodAnnotationDrivenBinder
     */
    enum Binder implements TargetMethodAnnotationDrivenBinder.ParameterBinder<DefaultCall> {

        
The singleton instance.

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

        
A reference to the target type method of the default call annotation.

/**
         * A reference to the target type method of the default call annotation.
         */
        private static final MethodDescription.InDefinedShape TARGET_TYPE;

        
A reference to the serializable proxy method of the default call annotation.

/**
         * A reference to the serializable proxy method of the default call annotation.
         */
        private static final MethodDescription.InDefinedShape SERIALIZABLE_PROXY;

        
A reference to the null if possible method of the default call annotation.

/**
         * A reference to the null if possible method of the default call annotation.
         */
        private static final MethodDescription.InDefinedShape NULL_IF_IMPOSSIBLE;

        /*
         * Looks up method constants of the default call annotation.
         */
        static {
            MethodList<MethodDescription.InDefinedShape> annotationProperties = TypeDescription.ForLoadedType.of(DefaultCall.class).getDeclaredMethods();
            TARGET_TYPE = annotationProperties.filter(named("targetType")).getOnly();
            SERIALIZABLE_PROXY = annotationProperties.filter(named("serializableProxy")).getOnly();
            NULL_IF_IMPOSSIBLE = annotationProperties.filter(named("nullIfImpossible")).getOnly();
        }

        
{@inheritDoc}

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

        
{@inheritDoc}

/**
         * {@inheritDoc}
         */
        public MethodDelegationBinder.ParameterBinding<?> bind(AnnotationDescription.Loadable<DefaultCall> annotation,
                                                               MethodDescription source,
                                                               ParameterDescription target,
                                                               Implementation.Target implementationTarget,
                                                               Assigner assigner,
                                                               Assigner.Typing typing) {
            TypeDescription targetType = target.getType().asErasure();
            if (!targetType.represents(Runnable.class) && !targetType.represents(Callable.class) && !targetType.represents(Object.class)) {
                throw new IllegalStateException("A default method call proxy can only be assigned to Runnable or Callable types: " + target);
            } else if (source.isConstructor()) {
                return annotation.getValue(NULL_IF_IMPOSSIBLE).resolve(Boolean.class)
                        ? new MethodDelegationBinder.ParameterBinding.Anonymous(NullConstant.INSTANCE)
                        : MethodDelegationBinder.ParameterBinding.Illegal.INSTANCE;
            }
            TypeDescription typeDescription = annotation.getValue(TARGET_TYPE).resolve(TypeDescription.class);
            Implementation.SpecialMethodInvocation specialMethodInvocation = (typeDescription.represents(void.class)
                    ? DefaultMethodLocator.Implicit.INSTANCE
                    : new DefaultMethodLocator.Explicit(typeDescription)).resolve(implementationTarget, source).withCheckedCompatibilityTo(source.asTypeToken());
            StackManipulation stackManipulation;
            if (specialMethodInvocation.isValid()) {
                stackManipulation = new MethodCallProxy.AssignableSignatureCall(specialMethodInvocation, annotation.getValue(SERIALIZABLE_PROXY).resolve(Boolean.class));
            } else if (annotation.load().nullIfImpossible()) {
                stackManipulation = NullConstant.INSTANCE;
            } else {
                return MethodDelegationBinder.ParameterBinding.Illegal.INSTANCE;
            }
            return new MethodDelegationBinder.ParameterBinding.Anonymous(stackManipulation);
        }

        
A default method locator is responsible for looking up a default method to a given source method.

/**
         * A default method locator is responsible for looking up a default method to a given source method.
         */
        protected interface DefaultMethodLocator {

            
Locates the correct default method to a given source method.

Params:
  • implementationTarget – The current implementation target.
  • source –               The source method for which a default method should be looked up.
Returns:A special method invocation of the default method or an illegal special method invocation,
if no suitable invocation could be located.
/**
             * Locates the correct default method to a given source method.
             *
             * @param implementationTarget The current implementation target.
             * @param source               The source method for which a default method should be looked up.
             * @return A special method invocation of the default method or an illegal special method invocation,
             * if no suitable invocation could be located.
             */
            Implementation.SpecialMethodInvocation resolve(Implementation.Target implementationTarget, MethodDescription source);

            
An implicit default method locator that only permits the invocation of a default method if the source
method itself represents a method that was defined on a default method interface.

/**
             * An implicit default method locator that only permits the invocation of a default method if the source
             * method itself represents a method that was defined on a default method interface.
             */
            enum Implicit implements DefaultMethodLocator {

                
The singleton instance.

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

                
{@inheritDoc}

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

            
An explicit default method locator attempts to look up a default method in the specified interface type.

/**
             * An explicit default method locator attempts to look up a default method in the specified interface type.
             */
            @HashCodeAndEqualsPlugin.Enhance
            class Explicit implements DefaultMethodLocator {

                
A description of the type on which the default method should be invoked.

/**
                 * A description of the type on which the default method should be invoked.
                 */
                private final TypeDescription typeDescription;

                
Creates a new explicit default method locator.

Params:
/**
                 * Creates a new explicit default method locator.
                 *
                 * @param typeDescription The actual target interface as explicitly defined by
                 *                        {@link DefaultCall#targetType()}.
                 */
                public Explicit(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(), typeDescription);
                }
            }
        }
    }
}