package net.bytebuddy.implementation.bind.annotation;
import lombok.EqualsAndHashCode;
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 {@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.
*
* @return {@code true} if this method instance should be cached.
*/
boolean cached() default true;
/**
* 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 {@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 {@link DefaultMethod} annotation.
*/
enum Binder implements TargetMethodAnnotationDrivenBinder.ParameterBinder<DefaultMethod> {
/**
* The singleton instance.
*/
INSTANCE;
/**
* The {@link DefaultMethod#cached()} property.
*/
private static final MethodDescription.InDefinedShape CACHED;
/**
* 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 = new TypeDescription.ForLoadedType(DefaultMethod.class).getDeclaredMethods();
CACHED = methodList.filter(named("cached")).getOnly();
TARGET_TYPE = methodList.filter(named("targetType")).getOnly();
NULL_IF_IMPOSSIBLE = methodList.filter(named("nullIfImpossible")).getOnly();
}
@Override
public Class<DefaultMethod> getHandledType() {
return DefaultMethod.class;
}
@Override
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);
if (specialMethodInvocation.isValid()) {
return new MethodDelegationBinder.ParameterBinding.Anonymous(new DelegationMethod(specialMethodInvocation, annotation.getValue(CACHED).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.
*/
protected interface MethodLocator {
/**
* 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.
*/
enum ForImplicitType implements MethodLocator {
/**
* The singleton instance.
*/
INSTANCE;
@Override
public Implementation.SpecialMethodInvocation resolve(Implementation.Target implementationTarget, MethodDescription source) {
return implementationTarget.invokeDefault(source.asSignatureToken());
}
}
/**
* A method locator for an explicit target type.
*/
@EqualsAndHashCode
class ForExplicitType implements MethodLocator {
/**
* The explicit target type.
*/
private final TypeDescription typeDescription;
/**
* Creates a method locator for an explicit target.
*
* @param typeDescription The explicit target type.
*/
protected ForExplicitType(TypeDescription typeDescription) {
this.typeDescription = typeDescription;
}
@Override
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.
*/
@EqualsAndHashCode
protected static class DelegationMethod implements StackManipulation {
/**
* The special method invocation that represents the super method call.
*/
private final Implementation.SpecialMethodInvocation specialMethodInvocation;
/**
* {@code true} if the method constant should be cached.
*/
private final boolean cached;
/**
* 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.
*/
protected DelegationMethod(Implementation.SpecialMethodInvocation specialMethodInvocation, boolean cached) {
this.specialMethodInvocation = specialMethodInvocation;
this.cached = cached;
}
@Override
public boolean isValid() {
return specialMethodInvocation.isValid();
}
@Override
public Size apply(MethodVisitor methodVisitor, Implementation.Context implementationContext) {
StackManipulation stackManipulation = MethodConstant.forMethod(implementationContext.registerAccessorFor(specialMethodInvocation,
MethodAccessorFactory.AccessType.PUBLIC));
return (cached
? FieldAccess.forField(implementationContext.cache(stackManipulation, new TypeDescription.ForLoadedType(Method.class))).read()
: stackManipulation).apply(methodVisitor, implementationContext);
}
}
}
}