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 Redistribution and use in source and binary forms, with or without 37 modification, are permitted provided that the following conditions are 38 met: 39 * Redistributions of source code must retain the above copyright 40 notice, this list of conditions and the following disclaimer. 41 * Redistributions in binary form must reproduce the above copyright 42 notice, this list of conditions and the following disclaimer in the 43 documentation and/or other materials provided with the distribution. 44 * Neither the name of the copyright holder nor the names of 45 contributors may be used to endorse or promote products derived from 46 this software without specific prior written permission. 47 48 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS 49 IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 50 TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 51 PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER 52 BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 53 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 54 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 55 BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 56 WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 57 OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 58 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 59 */ 60 61 package jdk.dynalink.linker; 62 63 import java.lang.invoke.MethodHandles; 64 import java.util.function.Supplier; 65 import jdk.dynalink.SecureLookupSupplier; 66 import jdk.dynalink.beans.BeansLinker; 67 import jdk.dynalink.linker.support.TypeUtilities; 68 69 /** 70 * Optional interface that can be implemented by {@link GuardingDynamicLinker} 71 * implementations to provide language-specific type conversion capabilities. 72 * Note that if you implement this interface, you will very likely want to 73 * implement {@link ConversionComparator} interface too, as your additional 74 * language-specific conversions, in absence of a strategy for prioritizing 75 * these conversions, will cause more ambiguity for {@link BeansLinker} in 76 * selecting the correct overload when trying to link to an overloaded Java 77 * method. 78 */ 79 public interface GuardingTypeConverterFactory { 80 /** 81 * Returns a guarded type conversion that receives a value of the specified 82 * source type and returns a value converted to the specified target type. 83 * Value types can be either primitives or reference types, including 84 * interfaces, so you can even provide converters for converting your 85 * language's objects to Java interfaces and classes by generating adapters 86 * for them. 87 * <p> 88 * The type of the invocation is <code>(sourceType)→targetType</code>, while the 89 * type of the guard is <code>(sourceType)→boolean</code>. You are allowed to 90 * return unconditional invocations (with no guard) if the source type is 91 * specific to your runtime and your runtime only. 92 * <p>Note that this method will never be invoked for 93 * {@link TypeUtilities#isMethodInvocationConvertible(Class, Class) method 94 * invocation conversions} as those can be automatically applied by 95 * {@link java.lang.invoke.MethodHandle#asType(MethodType)}. 96 * An implementation can assume it is never requested to produce a 97 * converter for those conversions. If a language runtime needs to customize 98 * method invocation conversions, it should 99 * {@link jdk.dynalink.DynamicLinkerFactory#setAutoConversionStrategy(MethodTypeConversionStrategy) 100 * set an autoconversion strategy in the dynamic linker factory} instead. 101 * <p>Dynalink is at liberty to either cache some of the returned converters 102 * or to repeatedly request the converter factory to create the same 103 * conversion. 104 * 105 * @param sourceType source type 106 * @param targetType the target type. 107 * @param lookupSupplier a supplier for retrieving the lookup of the class 108 * on whose behalf a type converter is requested. When a converter is 109 * requested as part of linking an {@code invokedynamic} instruction the 110 * supplier will return the lookup passed to the bootstrap method, otherwise 111 * if the method is invoked from within a 112 * {@link LinkerServices#getWithLookup(Supplier, jdk.dynalink.SecureLookupSupplier)} 113 * it will delegate to the secure lookup supplier. In any other case, 114 * it will return the public lookup. A typical case where the lookup might 115 * be needed is when the converter creates a Java adapter class on the fly 116 * (e.g. to convert some object from the dynamic language into a Java 117 * interface for interoperability). Invoking the {@link Supplier#get()} 118 * method on the passed supplier will be subject to the same security checks 119 * as {@link SecureLookupSupplier#getLookup()}. An implementation should avoid 120 * retrieving the lookup if it is not needed so as to avoid the expense of 121 * {@code AccessController.doPrivileged} call. 122 * @return a guarded invocation that can take an object (if it passes guard) 123 * and return another object that is its representation coerced into the 124 * target type. In case the factory is certain it is unable to handle a 125 * conversion, it can return null. In case the factory is certain that it 126 * can always handle the conversion, it can return an unconditional 127 * invocation (one whose guard is null). 128 * @throws Exception if there was an error during creation of the converter 129 * @see LinkerServices#getWithLookup(Supplier, SecureLookupSupplier) 130 */ convertToType(Class<?> sourceType, Class<?> targetType, Supplier<MethodHandles.Lookup> lookupSupplier)131 public GuardedInvocation convertToType(Class<?> sourceType, Class<?> targetType, Supplier<MethodHandles.Lookup> lookupSupplier) throws Exception; 132 } 133