PropertiesURLReader.java

package org.nnsoft.guice.rocoto.configuration;

/*
 *    Copyright 2009-2012 The 99 Software Foundation
 *
 *    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.
 */

import static com.google.common.base.Preconditions.checkNotNull;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.Properties;

import org.nnsoft.guice.rocoto.configuration.binder.XMLPropertiesFormatBindingBuilder;

/**
 * {@link Properties} reader implementation able to read configuration files from classpath, file system or URLs.
 *
 * This reader implementation support both {@code .properties} and {@code .xml} properties format.
 */
final class PropertiesURLReader
    implements XMLPropertiesFormatBindingBuilder
{

    /**
     * The URL has to be open.
     */
    private final URL url;

    /**
     * Flag to mark properties are in XML format.
     */
    private boolean isXML = false;

    /**
     * Create a new {@code .properties} reader of a resource located in the given URL.
     *
     * @param url the URL that locates the configuration resource.
     * @param isXML to mark if the properties file is in XML format or not.
     */
    public PropertiesURLReader( URL url )
    {
        checkNotNull( url, "'url' argument can't be null" );

        this.url = url;
    }

    /**
     * {@inheritDoc}
     */
    public void inXMLFormat()
    {
        isXML = true;
    }

    /**
     *
     * @return
     */
    public URL getUrl()
    {
        return url;
    }

    /**
     *
     *
     * @return
     * @throws Exception
     */
    public final Properties readConfiguration()
        throws Exception
    {
        URLConnection connection = null;
        InputStream input = null;
        try
        {
            connection = url.openConnection();
            connection.setUseCaches( false );
            input = connection.getInputStream();

            Properties properties = new Properties();
            if ( isXML )
            {
                properties.loadFromXML( input );
            }
            else
            {
                properties.load( input );
            }

            return properties;
        }
        finally
        {
            if ( connection != null && ( connection instanceof HttpURLConnection ) )
            {
                ( (HttpURLConnection) connection ).disconnect();
            }
            if ( input != null )
            {
                try
                {
                    input.close();
                }
                catch ( IOException e )
                {
                    // close quietly
                }
            }
        }
    }

}