languageservlet.java

这个weblogging 设计得比较精巧

/*
 * Filename: LanguageServlet.java
 * 
 * Created on 02-May-04
 */
package org.roller.presentation.velocity;

import java.util.Locale;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.Globals;
import org.apache.velocity.Template;
import org.apache.velocity.context.Context;
import org.roller.presentation.LanguageUtil;
import org.roller.presentation.RollerContext;

/**
 * Changes the language of the current Locale to the language specified
 * by the user. The new language must be supported by Roller.  
 * 
 * And new supported languages to the web.servlet-init-param value. Make sure you add language-only
 * values at the end of a chain. So "en_US,en" instead of "en,en_US". And no spaces.
 * 
 * @web.servlet name="LanguageServlet" load-on-startup="10"
 * @web.servlet-init-param name="org.roller.presentation.supported.languages" value="en,nl,zh_cn,zh_tw,vi"
 *  
 * @web.servlet-mapping url-pattern="/language/*"
 * 
 * @author <a href="mailto:[e-mail]">Jaap van der Molen</a>
 * @version $Revision: 1.8 $
 */
public class LanguageServlet extends BasePageServlet
{
    static final long serialVersionUID = -6548723098429557183L;
    
	/**
	 * Logger
	 */
	private static Log mLogger =
		LogFactory.getFactory().getInstance(LanguageServlet.class);

	/**
	 * @see org.roller.presentation.velocity.BasePageServlet#init(javax.servlet.ServletConfig)
	 */
	public void init(ServletConfig config) throws ServletException
	{
		super.init(config);

		// load supported languages
		ServletContext ctx = config.getServletContext();
		String supportedLanguages =
			config.getInitParameter(LanguageUtil.SUPPORTED_LANGUAGES);
		if (supportedLanguages != null
			&& supportedLanguages.trim().length() > 0)
		{
			// extract langauges
			ctx.setAttribute(
				LanguageUtil.SUPPORTED_LANGUAGES,
				LanguageUtil.extractLanguages(supportedLanguages));
		}
	}

	/**
	 * @see org.roller.presentation.velocity.BasePageServlet#handleRequest(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, org.apache.velocity.context.Context)
	 */
	public Template handleRequest(
		HttpServletRequest request,
		HttpServletResponse response,
		Context ctx) throws Exception
	{
		mLogger.debug("Processing language change...");
        ServletContext servletContext = RollerContext.getServletContext();
        
		Locale[] supportedLanguages =
			LanguageUtil.getSupportedLanguages(servletContext);

		if (supportedLanguages == null || supportedLanguages.length == 0)
		{
			// add error message
			ctx.put("languageError", "Unable to switch language: no supported languages defined.");
			// proceed with request serving
			return super.handleRequest(request, response, ctx);
		}

		String newLang = request.getParameter("language");
		mLogger.debug("New language in Request: " + newLang);
		if (newLang == null || newLang.length() == 0) {
			// add error message
			ctx.put("languageError", "Unable to switch language: no new language specified.");
			// proceed with request serving
			return super.handleRequest(request, response, ctx);
		}
		
		Locale newLocale = LanguageUtil.createLocale(newLang);

		// verify if new language is supported
		if (!LanguageUtil.isSupported(newLocale, servletContext)) {
			// add error message
			ctx.put("languageError", "Unable to switch language: new language '"+newLang+"' is not supported.");
			// proceed with request serving
			return super.handleRequest(request, response, ctx);
		}

		// by now, all should be fine: change Locale
		HttpSession session = request.getSession();
		session.setAttribute(Globals.LOCALE_KEY, newLocale);
		mLogger.debug("Changed language to: " + newLocale);

		// proceed with request serving
		return super.handleRequest(request, response, ctx);
	}

}