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 */
017
018package org.apache.commons.configuration2;
019
020import java.util.Iterator;
021
022import org.apache.commons.configuration2.ex.ConfigurationException;
023import org.apache.commons.configuration2.io.FileHandler;
024import org.apache.commons.logging.Log;
025import org.apache.commons.logging.LogFactory;
026
027/**
028 * A configuration based on the system properties.
029 *
030 * @since 1.1
031 */
032public class SystemConfiguration extends MapConfiguration
033{
034    /** The logger. */
035    private static Log log = LogFactory.getLog(SystemConfiguration.class);
036
037    /**
038     * Create a Configuration based on the system properties.
039     *
040     * @see System#getProperties
041     */
042    public SystemConfiguration()
043    {
044        super(System.getProperties());
045    }
046
047    /**
048     * Sets system properties from a file specified by its file name. This is
049     * just a short cut for {@code setSystemProperties(null, fileName)}.
050     *
051     * @param fileName The name of the property file.
052     * @throws ConfigurationException if an error occurs.
053     * @since 1.6
054     */
055    public static void setSystemProperties(final String fileName)
056            throws ConfigurationException
057    {
058        setSystemProperties(null, fileName);
059    }
060
061    /**
062     * Sets system properties from a file specified using its base path and
063     * file name. The file can either be a properties file or an XML properties
064     * file. It is loaded, and all properties it contains are added to system
065     * properties.
066     *
067     * @param basePath The base path to look for the property file.
068     * @param fileName The name of the property file.
069     * @throws ConfigurationException if an error occurs.
070     * @since 1.6
071     */
072    public static void setSystemProperties(final String basePath, final String fileName)
073            throws ConfigurationException
074    {
075        final FileBasedConfiguration config =
076                fileName.endsWith(".xml") ? new XMLPropertiesConfiguration()
077                        : new PropertiesConfiguration();
078
079        final FileHandler handler = new FileHandler(config);
080        handler.setBasePath(basePath);
081        handler.setFileName(fileName);
082        handler.load();
083        setSystemProperties(config);
084    }
085
086    /**
087     * Set System properties from a configuration object.
088     * @param systemConfig The configuration containing the properties to be set.
089     * @since 1.6
090     */
091    public static void setSystemProperties(final Configuration systemConfig)
092    {
093        final Iterator<String> iter = systemConfig.getKeys();
094        while (iter.hasNext())
095        {
096            final String key = iter.next();
097            final String value = (String) systemConfig.getProperty(key);
098            if (log.isDebugEnabled())
099            {
100                log.debug("Setting system property " + key + " to " + value);
101            }
102            System.setProperty(key, value);
103        }
104    }
105
106    /**
107     * {@inheritDoc} This implementation returns a snapshot of the keys in the
108     * system properties. If another thread modifies system properties concurrently,
109     * these changes are not reflected by the iterator returned by this method.
110     */
111    @Override
112    protected Iterator<String> getKeysInternal()
113    {
114        return System.getProperties().stringPropertyNames().iterator();
115    }
116}