/*

 * Copyright (c) 2014, 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 com.sun.xml.internal.stream.buffer;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.text.MessageFormat;

import java.util.ResourceBundle;

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 static final String FAILED_TO_CREATE_NEW_INSTANCE = "FAILED_TO_CREATE_NEW_INSTANCE";

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

    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(format(FAILED_TO_CREATE_NEW_INSTANCE, getClass().getName()), e);

        }

    }

    private static String format(String property, Object... args) {

        String text = ResourceBundle.getBundle(ContextClassloaderLocal.class.getName()).getString(property);

        return MessageFormat.format(text, args);

    }

    private static ClassLoader getContextClassLoader() {

        return (ClassLoader)

                AccessController.doPrivileged(new PrivilegedAction() {

                    public Object run() {

                        ClassLoader cl = null;

                        try {

                            cl = Thread.currentThread().getContextClassLoader();

                        } catch (SecurityException ex) {

                        }

                        return cl;

                    }

                });

    }

}