001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.vfs2.util;
018
019/**
020 * Factory to create an instance of a Cryptor.
021 *
022 * @since 2.0
023 */
024public final class CryptorFactory {
025    /**
026     * The System property name to identify the Cryptor class to be used.
027     */
028    public static final String CRYPTOR_CLASS = "org.apache.commons.vfs2.cryptor";
029
030    private static Cryptor instance;
031
032    /**
033     * Prevent instantiation of the class.
034     */
035    private CryptorFactory() {
036
037    }
038
039    /**
040     * Allows the Cryptor class to be set programmatically.
041     *
042     * @param cryptor The Cryptor.
043     */
044    public static synchronized void setCryptor(final Cryptor cryptor) {
045        instance = cryptor;
046    }
047
048    /**
049     * Return the Cryptor. If one has not been previously set, create it. The Cryptor class can be set by setting the
050     * "org.apache.commons.vfs2.cryptor" System property to the name of the Cryptor class.
051     *
052     * @return The Cryptor.
053     */
054    public static synchronized Cryptor getCryptor() {
055        if (instance != null) {
056            return instance;
057        }
058
059        final String cryptorClass = System.getProperty(CRYPTOR_CLASS);
060        if (cryptorClass != null) {
061            try {
062                final Class<?> clazz = Class.forName(cryptorClass);
063                instance = (Cryptor) clazz.newInstance();
064                return instance;
065            } catch (final Exception ex) {
066                throw new RuntimeException("Unable to create Cryptor " + cryptorClass, ex);
067            }
068        }
069        instance = new DefaultCryptor();
070        return instance;
071    }
072}