/**

  * Copyright 2012 Sven Diedrichsen 

  * 

  * Licensed under the Apache License, Version 2.0 (the "License"); 

  * you may not use this file except in compliance with the License. 

  * You may obtain a copy of the License at 

  * 

  * http://www.apache.org/licenses/LICENSE-2.0 

  * 

  * Unless required by applicable law or agreed to in writing, software 

  * distributed under the License is distributed on an 

  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either 

  * express or implied. See the License for the specific language 

  * governing permissions and limitations under the License. 

  */

 package de.jollyday.configuration.impl;

 import java.io.InputStream;

 import java.net.URL;

 import java.util.Properties;

 import java.util.logging.Level;

 import java.util.logging.Logger;

 import de.jollyday.configuration.ConfigurationProvider;

 /**

  * An {@link ConfigurationProvider} implementation which reads a list of URLs

  * provided by the system property 'de.jollyday.config.urls' in order they are

  * provided into a {@link Properties} instance.

  * 

  * @author Sven Diedrichsen

  */

 public class URLConfigurationProvider implements ConfigurationProvider {

         private static final Logger LOG = Logger

                         .getLogger(URLConfigurationProvider.class.getName());

         /**

          * Returns the properties by reading from the URLs provided by the system

          * property 'de.jollyday.config.urls'.

          */

         @Override

         public Properties getProperties() {

                 Properties properties = new Properties();

                 Properties systemProps = System.getProperties();

                 String configURLs = systemProps.getProperty(CONFIG_URLS_PROPERTY);

                 if (configURLs != null) {

                         String[] strConfigURLs = configURLs.split(",");

                         if (strConfigURLs != null) {

                                 for (String strURL : strConfigURLs) {

                                         readPropertiesFromURL(properties, strURL);

                                 }

                         }

                 }

                 return properties;

         }

         private void readPropertiesFromURL(Properties properties, String strURL) {

                 if (strURL == null || "".equals(strURL))

                         return;

                 InputStream inputStream = null;

                 try {

                         URL configURL = new URL(strURL.trim());

                         inputStream = configURL.openStream();

                         properties.load(inputStream);

                 } catch (Exception e) {

                         LOG.log(Level.WARNING, "Cannot read configuration from '" + strURL

                                         + "'.", e);

                 } finally {

                         closeStreamFromURL(strURL, inputStream);

                 }

         }

         private void closeStreamFromURL(String strURL, InputStream inputStream) {

                 if (inputStream != null) {

                         try {

                                 inputStream.close();

                         } catch (Exception e) {

                                 LOG.warning("Cannot close stream for configuration URL "

                                                 + strURL + ".");

                         }

                 }

         }

 }