/**
 * Copyright(c) 2006 Somchai LIMSIRORATANA. All Rights Reserved.
 *
 * 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 java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/** Filter a null character encoding of request.
 * Some browser does not sent character encoding type of request to server.
 * Then, the character encoding of request will be null.
 * The server such as Tomcat use ISO-8859-1 by default.
 * This filter will detect the null character encoding of request.
 * Then, set the request character encoding corresponse to the response character encoding.
 *
 * @author Somchai LIMSIRORATANA
 * @version 1.0
 */

public final class RequestCharacterEncodingFilter implements Filter {
	private FilterConfig config = null;
	private String encoding = null;
	
	public void init(FilterConfig filterConfig)
		throws ServletException {

   		config = filterConfig;
   		encoding = config.getInitParameter("encoding");
   		config.getServletContext().log("Initialize Filter: "+config.getFilterName()+" with encoding="+encoding);
	}
	
	public void destroy() {
   		config.getServletContext().log("Destroy Filter: "+config.getFilterName());
    	config = null;
    	encoding = null;
    }
    
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
		throws IOException, ServletException {
			
   		if (request.getCharacterEncoding() == null) {
      		request.setCharacterEncoding(encoding);
  		}
   		chain.doFilter(request, response);
	}
}