1 /*

     2  * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 /*

    27  * This file is available under and governed by the GNU General Public

    28  * License version 2 only, as published by the Free Software Foundation.

    29  * However, the following notice accompanied the original version of this

    30  * file, and Oracle licenses the original version of this file under the BSD

    31  * license:

    32  */

    33 /*

    34    Copyright 2009-2013 Attila Szegedi

    35 

    36    Licensed under both the Apache License, Version 2.0 (the "Apache License")

    37    and the BSD License (the "BSD License"), with licensee being free to

    38    choose either of the two at their discretion.

    39 

    40    You may not use this file except in compliance with either the Apache

    41    License or the BSD License.

    42 

    43    If you choose to use this file in compliance with the Apache License, the

    44    following notice applies to you:

    45 

    46        You may obtain a copy of the Apache License at

    47 

    48            http://www.apache.org/licenses/LICENSE-2.0

    49 

    50        Unless required by applicable law or agreed to in writing, software

    51        distributed under the License is distributed on an "AS IS" BASIS,

    52        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or

    53        implied. See the License for the specific language governing

    54        permissions and limitations under the License.

    55 

    56    If you choose to use this file in compliance with the BSD License, the

    57    following notice applies to you:

    58 

    59        Redistribution and use in source and binary forms, with or without

    60        modification, are permitted provided that the following conditions are

    61        met:

    62        * Redistributions of source code must retain the above copyright

    63          notice, this list of conditions and the following disclaimer.

    64        * Redistributions in binary form must reproduce the above copyright

    65          notice, this list of conditions and the following disclaimer in the

    66          documentation and/or other materials provided with the distribution.

    67        * Neither the name of the copyright holder nor the names of

    68          contributors may be used to endorse or promote products derived from

    69          this software without specific prior written permission.

    70 

    71        THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS

    72        IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED

    73        TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A

    74        PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER

    75        BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

    76        CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

    77        SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR

    78        BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,

    79        WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR

    80        OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF

    81        ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

    82 */

    83 

    84 package jdk.internal.dynalink.linker;

    85 

    86 import java.lang.invoke.MethodHandles;

    87 import java.util.function.Supplier;

    88 import jdk.internal.dynalink.CallSiteDescriptor;

    89 import jdk.internal.dynalink.beans.BeansLinker;

    90 import jdk.internal.dynalink.linker.support.TypeUtilities;

    91 

    92 /**

    93  * Optional interface that can be implemented by {@link GuardingDynamicLinker}

    94  * implementations to provide language-specific type conversion capabilities.

    95  * Note that if you implement this interface, you will very likely want to

    96  * implement {@link ConversionComparator} interface too, as your additional

    97  * language-specific conversions, in absence of a strategy for prioritizing

    98  * these conversions, will cause more ambiguity for {@link BeansLinker} in

    99  * selecting the correct overload when trying to link to an overloaded Java

   100  * method.

   101  */

   102 public interface GuardingTypeConverterFactory {

   103     /**

   104      * Returns a guarded type conversion that receives a value of the specified

   105      * source type and returns a value converted to the specified target type.

   106      * Value types can be either primitives or reference types, including

   107      * interfaces, so you can even provide converters for converting your

   108      * language's objects to Java interfaces and classes by generating adapters

   109      * for them.

   110      * <p>

   111      * The type of the invocation is {@code targetType(sourceType)}, while the

   112      * type of the guard is {@code boolean(sourceType)}. You are allowed to

   113      * return unconditional invocations (with no guard) if the source type is

   114      * specific to your runtime and your runtime only.

   115      * <p>Note that this method will never be invoked for type conversions

   116      * allowed by the JLS 5.3 "Method Invocation Conversion", see

   117      * {@link TypeUtilities#isMethodInvocationConvertible(Class, Class)} for

   118      * details. An implementation can assume it is never requested to produce a

   119      * converter for these conversions.

   120      * <p>Dynalink is at liberty to either cache some of the returned converters

   121      * or to repeatedly request the converter factory to create the same

   122      * conversion.

   123      *

   124      * @param sourceType source type

   125      * @param targetType the target type.

   126      * @param lookupSupplier a supplier for retrieving the lookup of the class

   127      * on whose behalf a type converter is requested. When a converter is

   128      * requested as part of linking an {@code invokedynamic} instruction the

   129      * supplier will return the lookup passed to the bootstrap method, otherwise

   130      * it will return the public lookup. A typical case where the lookup might

   131      * be needed is when the converter creates a Java adapter class on the fly

   132      * (e.g. to convert some object from the dynamic language into a Java

   133      * interface for interoperability). Invoking the {@link Supplier#get()}

   134      * method on the passed supplier will be subject to the same security checks

   135      * as {@link CallSiteDescriptor#getLookup()}. An implementation should avoid

   136      * retrieving the lookup if it is not needed so as to avoid the expense of

   137      * {@code AccessController.doPrivileged} call.

   138      * @return a guarded invocation that can take an object (if it passes guard)

   139      * and return another object that is its representation coerced into the

   140      * target type. In case the factory is certain it is unable to handle a

   141      * conversion, it can return null. In case the factory is certain that it

   142      * can always handle the conversion, it can return an unconditional

   143      * invocation (one whose guard is null).

   144      * @throws Exception if there was an error during creation of the converter

   145      */

   146     public GuardedInvocation convertToType(Class<?> sourceType, Class<?> targetType, Supplier<MethodHandles.Lookup> lookupSupplier) throws Exception;

   147 }