me.lucko.shadow.DynamicClassTarget Maven / Gradle / Ivy

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/*
 * This file is part of shadow, licensed under the MIT License.
 *
 *  Copyright (c) lucko (Luck) 
 *  Copyright (c) contributors
 *
 *  Permission is hereby granted, free of charge, to any person obtaining a copy
 *  of this software and associated documentation files (the "Software"), to deal
 *  in the Software without restriction, including without limitation the rights
 *  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 *  copies of the Software, and to permit persons to whom the Software is
 *  furnished to do so, subject to the following conditions:
 *
 *  The above copyright notice and this permission notice shall be included in all
 *  copies or substantial portions of the Software.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 *  SOFTWARE.
 */

package me.lucko.shadow;

import org.checkerframework.checker.nullness.qual.NonNull;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.util.Optional;

/**
 * Defines a class target with a dynamic value, calculated on demand by a function.
 */
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface DynamicClassTarget {

    /**
     * Gets the loading function class.
     *
     * An instance of the function is retrieved/constructed on demand by the implementation in
     * the following order.
     * 
     * 
     * a static method named {@code getInstance} accepting no parameters and returning an instance of the implementation.
     * via a single enum constant, if the loading function class is an enum following the enum singleton pattern.
     * a static field named {@code instance} with the same type as and containing an instance of the implementation.
     * a static field named {@code INSTANCE} with the same type as and containing an instance of the implementation.
     * a no-args constructor
     * 
     *
     * Values defined for this property should be aware of this, and ensure an instance can be
     * retrieved/constructed.
     *
     * @return the loading function class
     */
    @NonNull Class value();

    /**
     * A functional interface encapsulating the target value computation.
     */
    @FunctionalInterface
    interface Function {
        /**
         * Computes the target class for the given {@code shadowClass}.
         *
         * @param shadowClass the shadow class to compute a target for
         * @return the target
         * @throws ClassNotFoundException if the resultant target class cannot be loaded
         */
        @NonNull Class computeClass(@NonNull Class shadowClass) throws ClassNotFoundException;
    }

    /**
     * A {@link TargetResolver} for the {@link DynamicClassTarget} annotation.
     */
    TargetResolver RESOLVER = new TargetResolver() {
        @Override
        public @NonNull Optional> lookupClass(@NonNull Class shadowClass) throws ClassNotFoundException {
            DynamicClassTarget annotation = shadowClass.getAnnotation(DynamicClassTarget.class);
            if (annotation == null) {
                return Optional.empty();
            }

            return Optional.of(Reflection.getInstance(DynamicClassTarget.Function.class, annotation.value()).computeClass(shadowClass));
        }
    };

}