wicket-extensions/src/java/wicket/extensions/util/encoding/CharSetUtil.java

/*
 * $Id$
 * $Revision$
 * $Date$
 *
 * ====================================================================
 * 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 wicket.extensions.util.encoding;

import java.io.IOException;
import java.io.InputStream;

import javax.servlet.ServletContext;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import wicket.RequestCycle;
import wicket.WicketRuntimeException;
import wicket.protocol.http.WebApplication;

/**
 * Utility class. Initialize Locale to character encoding mapping based on 
 * defaults and optionally a properties file CharSetMap.CHARSET_RESOURCE
 * to be found in WEB-INF.
 * 
 * @author Jonathan Locke
 * @author Juergen Donnerstag
 */
public class CharSetUtil
{
    /** Logging */
	private static Log log = LogFactory.getLog(CharSetUtil.class);

	/** Locale to character encoding mapping */
	private static CharSetMap charSetMap;

	/**
	 * Constructor
	 */
	public CharSetUtil()
	{
	}

	/**
	 * Initialize the mapping table based on defaults and optionally modified by 
	 * entries from a properties file to be found in WEB-INF.
	 * 
	 * @param application Wicket application object
	 */
	private synchronized static final void initialize(final WebApplication application)
	{
		if (charSetMap == null)
		{
			// Get servlet context
			final ServletContext context = application.getWicketServlet().getServletContext();
			
			final InputStream inputStream = context.getResourceAsStream("/WEB-INF/"
					+ CharSetMap.CHARSET_RESOURCE);
			
			if (inputStream == null)
			{
				charSetMap = new CharSetMap();
				if (log.isDebugEnabled())
				{
					log.debug("File '" + CharSetMap.CHARSET_RESOURCE + "' not found");
				}
			}
			else
			{
				try
				{
					charSetMap = new CharSetMap(inputStream);
				}
				catch (IOException ex)
				{
					throw new WicketRuntimeException("Error while reading CharSetMap", ex);
				}
			}
		}
	}

	/**
	 * Based on the Session's locale determine the associated character encoding.
	 * 
	 * @param cycle
	 * @return Char set to use for response.
	 */
	public final static String getEncoding(final RequestCycle cycle)
	{
		if (charSetMap == null)
		{
			initialize((WebApplication)cycle.getApplication());
		}

		return charSetMap.getCharSet(cycle.getSession().getLocale());
	}
}