languagefilter.java

一个实用工具类

/*
 * Copyright (C) butor.com. All rights reserved.
 *
 * This software is published under the terms of the GNU Library General
 * Public License (GNU LGPL), a copy of which has been included with this
 * distribution in the LICENSE.txt file. 
 */


package org.butor.web.filter;

import java.io.IOException;
import java.util.Locale;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.butor.config.Config;
import org.butor.config.lowlevel.IProperties;
import org.butor.log.Log;
import org.butor.web.Constants;
import org.butor.web.helper.StandardAttributes;

/**
 * @author sawanai
 *
 * This filter check for language setting and changes.
 */
public class LanguageFilter implements Filter {

	public final static String PROPERTY_HOST_LANGUAGE = "host_lang";
	
	public final static String PARAM_LANGUAGE = "lang";

	/**
	 * @see Filter#init(FilterConfig)
	 */
	public void init(FilterConfig config) throws ServletException {
	}

	/**
	 * @see Filter#destroy()
	 */
	public void destroy() {		
	}
	
	/**
	 * @see Filter#doFilter()
	 */
	public void doFilter(ServletRequest req, ServletResponse resp, FilterChain fc)
		throws ServletException, IOException {

		HttpServletRequest request = (HttpServletRequest) req;
		HttpServletResponse response = (HttpServletResponse) resp;
			
		Log.logStr(this, Log.LOG_TYPE_INFO, "doFilter()", "...");

		Cookie languageCookie = null;
		Locale locale = null;

		/* 
		 * FIRST, try to get lang from querystring.
		 * This parameter may be used to change the language at any time
		 * (even if the language cookie exists).
		 */
		String lang = request.getParameter(PARAM_LANGUAGE);

		if (lang != null) {
			Log.logStr(this, Log.LOG_TYPE_INFO, "doFilter()", 
				"Got request parameter lang=[" +lang +"]");
			
			languageCookie = new Cookie(Constants.LANGUAGE, lang);
			languageCookie.setMaxAge(365 * 24 * 60 * 60);
			languageCookie.setPath("/");
			response.addCookie(languageCookie);					

			locale = new Locale(lang);
			
		} else {
			Cookie[] cookies = request.getCookies();
			if (cookies != null) {
				for (int i = 0; i < cookies.length; i++) {
					Cookie cookie = cookies[i];
					if (cookie != null) {
						if (cookie.getName().equals(Constants.LANGUAGE)) {
							languageCookie = cookie;
							break;
						}
					}
				}
			}

			if (languageCookie != null) {
				Log.logStr(Log.LOG_LEVEL_MEDIUM, this, Log.LOG_TYPE_INFO, "doFilter()", 
					"Got language cookie=[" +languageCookie.getValue() +"]");
				locale = new Locale(languageCookie.getValue(), "");
			} 
		}
		
		/* 
		 * SECOND, if we have no locale yet, try to determine it from domain name
		 */
		if (locale == null) {
			String host = request.getServerName();
			IProperties properties = Config.getPropertyList(PROPERTY_HOST_LANGUAGE);
			if (properties != null) {
				lang = (String)properties.getProperty(host, Locale.ENGLISH.getLanguage());
				Log.logStr(Log.LOG_LEVEL_LOW, this, Log.LOG_TYPE_INFO, "doFilter()", 
					"Got lang from domain name, lang=[" +lang +"]");

			} else {
				lang = Locale.ENGLISH.getLanguage();
				Log.logStr(Log.LOG_LEVEL_LOW, this, Log.LOG_TYPE_INFO, "doFilter()", 
					"No lang parameter found! And, cant determine language by domain name!, Set default lang=[" +lang +"]");
			}

			if (lang != null) {
				languageCookie = new Cookie(Constants.LANGUAGE, lang);
				languageCookie.setMaxAge(365 * 24 * 60 * 60);
				languageCookie.setPath("/");
				response.addCookie(languageCookie);					
	
				locale = new Locale(lang);
			}
		}

		if (locale != null) {
			request.setAttribute(StandardAttributes.LOCALE_KEY, locale);
		}

		Log.logStr(this, Log.LOG_TYPE_INFO, "doFilter()", "done with locale [" +locale +"]");

		fc.doFilter(request, response);
	}
}