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