net.bytebuddy.dynamic.scaffold.subclass.ConstructorStrategy Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of byte-buddy Show documentation
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.
There is a newer version: 1.15.11
Show newest version
package net.bytebuddy.dynamic.scaffold.subclass;

import net.bytebuddy.description.method.MethodDescription;
import net.bytebuddy.description.method.MethodList;
import net.bytebuddy.description.type.TypeDescription;
import net.bytebuddy.description.type.generic.GenericTypeDescription;
import net.bytebuddy.dynamic.MethodTransformer;
import net.bytebuddy.dynamic.scaffold.MethodRegistry;
import net.bytebuddy.implementation.SuperMethodCall;
import net.bytebuddy.implementation.attribute.MethodAttributeAppender;
import net.bytebuddy.matcher.LatentMethodMatcher;

import java.util.Collections;
import java.util.List;

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

/**
 * A constructor strategy is responsible for creating bootstrap constructors for a
 * {@link SubclassDynamicTypeBuilder}.
 *
 * @see net.bytebuddy.dynamic.scaffold.subclass.ConstructorStrategy.Default
 */
public interface ConstructorStrategy {

    /**
     * Extracts constructors for a given super type. The extracted constructor signatures will then be imitated by the
     * created dynamic type.
     *
     * @param instrumentedType The type for which the constructors should be created.
     * @return A list of tokens that describe the constructors that are to be implemented.
     */
    List extractConstructors(TypeDescription instrumentedType);

    /**
     * Returns a method registry that is capable of creating byte code for the constructors that were
     * provided by the
     * {@link net.bytebuddy.dynamic.scaffold.subclass.ConstructorStrategy#extractConstructors(TypeDescription)}
     * method of this instance.
     *
     * @param methodRegistry                        The original method registry.
     * @param defaultMethodAttributeAppenderFactory The default method attribute appender factory.
     * @return A method registry that is capable of providing byte code for the constructors that were added by
     * this strategy.
     */
    MethodRegistry inject(MethodRegistry methodRegistry, MethodAttributeAppender.Factory defaultMethodAttributeAppenderFactory);

    /**
     * Default implementations of constructor strategies.
     */
    enum Default implements ConstructorStrategy {

        /**
         * This strategy is adding no constructors such that the instrumented type will by default not have any. This
         * is legal by Java byte code requirements. However, if no constructor is added manually if this strategy is
         * applied, the type is not constructable without using JVM non-public functionality.
         */
        NO_CONSTRUCTORS {
            @Override
            public List extractConstructors(TypeDescription superType) {
                return Collections.emptyList();
            }

            @Override
            public MethodRegistry inject(MethodRegistry methodRegistry, MethodAttributeAppender.Factory defaultMethodAttributeAppenderFactory) {
                return methodRegistry;
            }
        },

        /**
         * This strategy is adding a default constructor that calls it's super types default constructor. If no such
         * constructor is defined, an {@link IllegalArgumentException} is thrown. Note that the default constructor
         * needs to be visible to its sub type for this strategy to work.
         */
        DEFAULT_CONSTRUCTOR {
            @Override
            public List extractConstructors(TypeDescription instrumentedType) {
                TypeDescription superType = instrumentedType.getSuperType().asErasure();
                MethodList defaultConstructors = superType == null
                        ? new MethodList.Empty()
                        : superType.getDeclaredMethods().filter(isConstructor().and(takesArguments(0)).and(isVisibleTo(instrumentedType)));
                if (defaultConstructors.size() == 1) {
                    return defaultConstructors.asTokenList();
                } else {
                    throw new IllegalArgumentException(instrumentedType.getSuperType() + " declares no constructor that is visible to " + instrumentedType);
                }
            }

            @Override
            public MethodRegistry inject(MethodRegistry methodRegistry, MethodAttributeAppender.Factory defaultMethodAttributeAppenderFactory) {
                return methodRegistry.append(new LatentMethodMatcher.Resolved(isConstructor()),
                        new MethodRegistry.Handler.ForImplementation(SuperMethodCall.INSTANCE),
                        defaultMethodAttributeAppenderFactory,
                        MethodTransformer.NoOp.INSTANCE);
            }
        },

        /**
         * This strategy is adding all constructors of the instrumented type's super type where each constructor is
         * directly invoking its signature-equivalent super type constructor. Only constructors that are visible to the
         * instrumented type are added, i.e. package-private constructors are only added if the super type is defined
         * in the same package as the instrumented type and private constructors are always skipped.
         */
        IMITATE_SUPER_TYPE {
            @Override
            public List extractConstructors(TypeDescription instrumentedType) {
                GenericTypeDescription superType = instrumentedType.getSuperType();
                return (superType == null
                        ? new MethodList.Empty()
                        : superType.getDeclaredMethods().filter(isConstructor().and(isVisibleTo(instrumentedType)))).asTokenList();
            }

            @Override
            public MethodRegistry inject(MethodRegistry methodRegistry, MethodAttributeAppender.Factory defaultMethodAttributeAppenderFactory) {
                return methodRegistry.append(new LatentMethodMatcher.Resolved(isConstructor()),
                        new MethodRegistry.Handler.ForImplementation(SuperMethodCall.INSTANCE),
                        defaultMethodAttributeAppenderFactory,
                        MethodTransformer.NoOp.INSTANCE);
            }
        },

        /**
         * This strategy is adding all constructors of the instrumented type's super type where each constructor is
         * directly invoking its signature-equivalent super type constructor. Only {@code public} constructors are
         * added.
         */
        IMITATE_SUPER_TYPE_PUBLIC {
            @Override
            public List extractConstructors(TypeDescription instrumentedType) {
                GenericTypeDescription superType = instrumentedType.getSuperType();
                return (superType == null
                        ? new MethodList.Empty()
                        : superType.asErasure().getDeclaredMethods().filter(isPublic().and(isConstructor()))).asTokenList();
            }

            @Override
            public MethodRegistry inject(MethodRegistry methodRegistry, MethodAttributeAppender.Factory defaultMethodAttributeAppenderFactory) {
                return methodRegistry.append(new LatentMethodMatcher.Resolved(isConstructor()),
                        new MethodRegistry.Handler.ForImplementation(SuperMethodCall.INSTANCE),
                        defaultMethodAttributeAppenderFactory,
                        MethodTransformer.NoOp.INSTANCE);
            }
        };

        @Override
        public String toString() {
            return "ConstructorStrategy.Default." + name();
        }
    }
}