/* * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved. * 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, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package jdk.internal.loader; import java.util.Objects; import java.util.function.BiFunction; /** * root-ClassLoaderValue. Each instance defines a separate namespace for * associated values. *
* ClassLoaderValue allows associating a * {@link #computeIfAbsent(ClassLoader, BiFunction) computed} non-null value with * a {@code (ClassLoader, keys...)} tuple. The associated value, as well as the * keys are strongly reachable from the associated ClassLoader so care should be * taken to use such keys and values that only reference types resolvable from * the associated ClassLoader. Failing that, ClassLoader leaks are inevitable. *
* Example usage: *
{@code * // create a root instance which represents a namespace and declares the type of * // associated values (Class instances in this example) * static final ClassLoaderValue*> proxyClasses = new ClassLoaderValue<>(); * * // create a compound key composed of a Module and a list of interfaces * Module module = ...; * List > interfaces = ...; * ClassLoaderValue >.Sub .Sub >> key = * proxyClasses.sub(module).sub(interfaces); * * // use the compound key together with ClassLoader to lazily associate * // the value with tuple (loader, module, interfaces) and return it * ClassLoader loader = ...; * Class> proxyClass = key.computeIfAbsent(loader, (ld, ky) -> { * List
> intfcs = ky.key(); * Module m = ky.parent().key(); * Class> clazz = defineProxyClass(ld, m, intfcs); * return clazz; * }); * }
* {@code classLoaderValue.