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 * Creates an instance of {@link Cryptor}.
021 *
022 * @since 2.0
023 */
024public final class CryptorFactory {
025
026    /**
027     * The System property name to identify the Cryptor class to be used.
028     */
029    public static final String CRYPTOR_CLASS = "org.apache.commons.vfs2.cryptor";
030
031    private static Cryptor instance;
032
033    /**
034     * Gets the Cryptor. If one has not been previously set, create it. The Cryptor class can be set by setting the
035     * "org.apache.commons.vfs2.cryptor" System property to the name of the Cryptor class.
036     *
037     * @return The Cryptor.
038     */
039    public static synchronized Cryptor getCryptor() {
040        if (instance != null) {
041            return instance;
042        }
043
044        final String cryptorClass = System.getProperty(CRYPTOR_CLASS);
045        if (cryptorClass != null) {
046            try {
047                final Class<?> clazz = Class.forName(cryptorClass);
048                instance = (Cryptor) clazz.getConstructor().newInstance();
049                return instance;
050            } catch (final Exception ex) {
051                throw new IllegalStateException("Unable to create Cryptor " + cryptorClass, ex);
052            }
053        }
054        instance = new DefaultCryptor();
055        return instance;
056    }
057
058    /**
059     * Allows the Cryptor class to be set programmatically.
060     *
061     * @param cryptor The Cryptor.
062     */
063    public static synchronized void setCryptor(final Cryptor cryptor) {
064        instance = cryptor;
065    }
066
067    /**
068     * Prevent instantiation of the class.
069     */
070    private CryptorFactory() {
071
072    }
073}