src/java.xml.ws/share/classes/com/sun/xml/internal/ws/policy/sourcemodel/attach/ContextClassloaderLocal.java

/*
 * Copyright (c) 2014, 2017, 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
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package com.sun.xml.internal.ws.policy.sourcemodel.attach;

import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.WeakHashMap;

/**
 * Simple utility ensuring that the value is cached only in case it is non-internal implementation
 */
abstract class ContextClassloaderLocal<V> {

    private WeakHashMap<ClassLoader, V> CACHE = new WeakHashMap<>();

    public V get() throws Error {
        ClassLoader tccl = getContextClassLoader();
        V instance = CACHE.get(tccl);
        if (instance == null) {
            instance = createNewInstance();
            CACHE.put(tccl, instance);
        }
        return instance;
    }

    public void set(V instance) {
        CACHE.put(getContextClassLoader(), instance);
    }

    protected abstract V initialValue() throws Exception;

    private V createNewInstance() {
        try {
            return initialValue();
        } catch (Exception e) {
            throw new Error(ContextClassloaderLocalMessages.FAILED_TO_CREATE_NEW_INSTANCE(getClass().getName()), e);
        }
    }

    private static ClassLoader getContextClassLoader() {
        return AccessController.doPrivileged(new PrivilegedAction<ClassLoader>() {
            @Override
            public ClassLoader run() {
                ClassLoader cl = null;
                try {
                    cl = Thread.currentThread().getContextClassLoader();
                } catch (SecurityException ex) {
                }
                return cl;
            }
        });
    }
}