GuardingTypeConverterFactory.java revision 1551:f3b883bec2d0
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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 84package jdk.dynalink.linker; 85 86import java.lang.invoke.MethodHandles; 87import java.util.function.Supplier; 88import jdk.dynalink.CallSiteDescriptor; 89import jdk.dynalink.beans.BeansLinker; 90import jdk.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 */ 102public 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} 148