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    package org.apache.commons.discovery.tools;
018    
019    import java.util.Properties;
020    
021    import org.apache.commons.discovery.resource.ClassLoaders;
022    
023    /**
024     * Holder for a default class.
025     *
026     * Class may be specified by name (String) or class (Class).
027     * Using the holder complicates the users job, but minimized # of API's.
028     */
029    public class PropertiesHolder {
030    
031        private Properties properties;
032    
033        private final String propertiesFileName;
034    
035        /**
036         * Creates a new {@code PropertiesHolder} instance given an
037         * already load {@code Properties} set.
038         *
039         * @param properties The already load {@code Properties} set
040         */
041        public PropertiesHolder(Properties properties) {
042            this.properties = properties;
043            this.propertiesFileName = null;
044        }
045    
046        /**
047         * Creates a new {@code PropertiesHolder} instance given a
048         * property file name.
049         *
050         * @param propertiesFileName The property file name
051         */
052        public PropertiesHolder(String propertiesFileName) {
053            this.properties = null;
054            this.propertiesFileName = propertiesFileName;
055        }
056    
057        /**
058         * Returns the {@code Properties} instance, loaded if necessary from {@code propertiesFileName}.
059         *
060         * @param spi Optional SPI (may be null).
061         *            If provided, an attempt is made to load the
062         *            property file as-per Class.getResource().
063         *
064         * @param loaders Used only if properties need to be loaded.
065         * 
066         * @return The {@code Properties}, loaded if necessary.
067         */
068        public Properties getProperties(SPInterface<?> spi, ClassLoaders loaders) {
069            if (properties == null) {
070                properties = ResourceUtils.loadProperties(spi.getSPClass(), getPropertiesFileName(), loaders);
071            }
072            return properties;
073        }
074    
075        /**
076         * Returns the property file name
077         *
078         * @return The property file name
079         */
080        public String getPropertiesFileName() {
081            return propertiesFileName;
082        }
083    
084    }