Java example source code file (CompositeTypeBasedGuardingDynamicLinker.java)

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Java - Java tags/keywords

classtolinker, classvalue, compositetypebasedguardingdynamiclinker, exception, guardedinvocation, linkedlist, linkerservices, list, no_linker, object, override, serializable, suppresswarnings, typebasedguardingdynamiclinker, util

The CompositeTypeBasedGuardingDynamicLinker.java Java example source code

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
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 *
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/*
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file, and Oracle licenses the original version of this file under the BSD
 * license:
 */
/*
   Copyright 2009-2013 Attila Szegedi

   Licensed under both the Apache License, Version 2.0 (the "Apache License")
   and the BSD License (the "BSD License"), with licensee being free to
   choose either of the two at their discretion.

   You may not use this file except in compliance with either the Apache
   License or the BSD License.

   If you choose to use this file in compliance with the Apache License, the
   following notice applies to you:

       You may obtain a copy of the Apache 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.

   If you choose to use this file in compliance with the BSD License, the
   following notice applies to you:

       Redistribution and use in source and binary forms, with or without
       modification, are permitted provided that the following conditions are
       met:
       * Redistributions of source code must retain the above copyright
         notice, this list of conditions and the following disclaimer.
       * Redistributions in binary form must reproduce the above copyright
         notice, this list of conditions and the following disclaimer in the
         documentation and/or other materials provided with the distribution.
       * Neither the name of the copyright holder nor the names of
         contributors may be used to endorse or promote products derived from
         this software without specific prior written permission.

       THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
       IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
       TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
       PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
       BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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       WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

package jdk.internal.dynalink.support;

import java.io.Serializable;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import jdk.internal.dynalink.linker.GuardedInvocation;
import jdk.internal.dynalink.linker.GuardingDynamicLinker;
import jdk.internal.dynalink.linker.LinkRequest;
import jdk.internal.dynalink.linker.LinkerServices;
import jdk.internal.dynalink.linker.TypeBasedGuardingDynamicLinker;

/**
 * A composite type-based guarding dynamic linker. When a receiver of a not yet seen class is encountered, all linkers
 * are queried sequentially on their {@link TypeBasedGuardingDynamicLinker#canLinkType(Class)} method. The linkers
 * returning true are then bound to the class, and next time a receiver of same type is encountered, the linking is
 * delegated to those linkers only, speeding up dispatch.
 *
 * @author Attila Szegedi
 */
public class CompositeTypeBasedGuardingDynamicLinker implements TypeBasedGuardingDynamicLinker, Serializable {
    private static final long serialVersionUID = 1L;

    // Using a separate static class instance so there's no strong reference from the class value back to the composite
    // linker.
    private static class ClassToLinker extends ClassValue<List {
        private static final List<TypeBasedGuardingDynamicLinker> NO_LINKER = Collections.emptyList();
        private final TypeBasedGuardingDynamicLinker[] linkers;
        private final List<TypeBasedGuardingDynamicLinker>[] singletonLinkers;

        @SuppressWarnings("unchecked")
        ClassToLinker(TypeBasedGuardingDynamicLinker[] linkers) {
            this.linkers = linkers;
            singletonLinkers = new List[linkers.length];
            for(int i = 0; i < linkers.length; ++i) {
                singletonLinkers[i] = Collections.singletonList(linkers[i]);
            }
        }

        @Override
        protected List<TypeBasedGuardingDynamicLinker> computeValue(Class clazz) {
            List<TypeBasedGuardingDynamicLinker> list = NO_LINKER;
            for(int i = 0; i < linkers.length; ++i) {
                final TypeBasedGuardingDynamicLinker linker = linkers[i];
                if(linker.canLinkType(clazz)) {
                    switch(list.size()) {
                        case 0: {
                            list = singletonLinkers[i];
                            break;
                        }
                        case 1: {
                            list = new LinkedList<>(list);
                        }
                        //$FALL-THROUGH$
                        default: {
                            list.add(linker);
                        }
                    }
                }
            }
            return list;
        }
    }

    private final ClassValue<List classToLinker;

    /**
     * Creates a new composite type-based linker.
     *
     * @param linkers the component linkers
     */
    public CompositeTypeBasedGuardingDynamicLinker(Iterable<? extends TypeBasedGuardingDynamicLinker> linkers) {
        final List<TypeBasedGuardingDynamicLinker> l = new LinkedList<>();
        for(TypeBasedGuardingDynamicLinker linker: linkers) {
            l.add(linker);
        }
        this.classToLinker = new ClassToLinker(l.toArray(new TypeBasedGuardingDynamicLinker[l.size()]));
    }

    @Override
    public boolean canLinkType(Class<?> type) {
        return !classToLinker.get(type).isEmpty();
    }

    @Override
    public GuardedInvocation getGuardedInvocation(LinkRequest linkRequest, final LinkerServices linkerServices)
            throws Exception {
        final Object obj = linkRequest.getReceiver();
        if(obj == null) {
            return null;
        }
        for(TypeBasedGuardingDynamicLinker linker: classToLinker.get(obj.getClass())) {
            final GuardedInvocation invocation = linker.getGuardedInvocation(linkRequest, linkerServices);
            if(invocation != null) {
                return invocation;
            }
        }
        return null;
    }

    /**
     * Optimizes a list of type-based linkers. If a group of adjacent linkers in the list all implement
     * {@link TypeBasedGuardingDynamicLinker}, they will be replaced with a single instance of
     * {@link CompositeTypeBasedGuardingDynamicLinker} that contains them.
     *
     * @param linkers the list of linkers to optimize
     * @return the optimized list
     */
    public static List<GuardingDynamicLinker> optimize(Iterable linkers) {
        final List<GuardingDynamicLinker> llinkers = new LinkedList<>();
        final List<TypeBasedGuardingDynamicLinker> tblinkers = new LinkedList<>();
        for(GuardingDynamicLinker linker: linkers) {
            if(linker instanceof TypeBasedGuardingDynamicLinker) {
                tblinkers.add((TypeBasedGuardingDynamicLinker)linker);
            } else {
                addTypeBased(llinkers, tblinkers);
                llinkers.add(linker);
            }
        }
        addTypeBased(llinkers, tblinkers);
        return llinkers;
    }

    private static void addTypeBased(List<GuardingDynamicLinker> llinkers,
            List<TypeBasedGuardingDynamicLinker> tblinkers) {
        switch(tblinkers.size()) {
            case 0: {
                break;
            }
            case 1: {
                llinkers.addAll(tblinkers);
                tblinkers.clear();
                break;
            }
            default: {
                llinkers.add(new CompositeTypeBasedGuardingDynamicLinker(tblinkers));
                tblinkers.clear();
                break;
            }
        }
    }
}