怎么实现基于filter的html静态化

public class HtmlStaticFilter implements Filter {

	private static final Log log = LogFactory.getLog(HtmlStaticFilter.class);

	private Xcache xcache;

	public Xcache getXcache() {
		return xcache;
	}

	public void setXcache(Xcache xcache) {
		this.xcache = xcache;
	}

	private static int counter = 0;

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain filterChain) throws ServletException, IOException {

		String refresh = request.getParameter("refresh");
		if (StringUtils.isNotBlank(refresh) &&refresh.equals("true")) {
			filterChain.doFilter(request, response);
			return;
		}

		/**
		 * 获取请求url作为缓存的KEY
		 */
		String urlKey = request.getServerName()
				+ ((HttpServletRequest) request).getRequestURI();

		// 不缓存非html请求. js css img 跳过
		if (!urlKey.endsWith(".html") && !urlKey.endsWith("/")) {
			filterChain.doFilter(request, response);
			return;
		}
		log.error(++counter + ":url=====>" + urlKey);
		/**
		 * 查看缓存中是否有此文件,如果有，返回文件
		 */
		String content = (String) xcache.get(urlKey);
		if (content == null) {
			log.error("content=====>" + content);// 应该只出现一次
			// 使用我们自定义的响应包装器来包装原始的ServletResponse
			ResponseWrapper wrapper = new ResponseWrapper(
					(HttpServletResponse) response);
			/**
			 * 如果没有，继续请求，获取请求后返回的结果，放入缓存中。
			 */
			// 这句话非常重要，注意看到第二个参数是我们的包装器而不是response
			filterChain.doFilter(request, wrapper);
			// 处理截获的结果并进行处理，比如替换所有的“名称”为“铁木箱子”
			content = wrapper.getResult();
			xcache.set(urlKey, content);
		}

		/**
		 * 返回请求结果给客户端
		 */
		response.setCharacterEncoding("UTF-8");
		// 重置响应输出的内容长度
		response.setContentLength(-1);
		// 输出最终的结果
		PrintWriter out = response.getWriter();
		out.write(content);
		out.flush();
		out.close();
	}

	@Override
	public void destroy() {

	}

	@Override
	public void init(FilterConfig arg0) throws ServletException {

	}

}

/**
 * 自定义一个响应结果包装器，将在这里提供一个基于内存的输出器来存储所有 返回给客户端的原始HTML代码。
 * 
 * @author 铁木箱子
 * 
 */
public class ResponseWrapper extends HttpServletResponseWrapper {
	private PrintWriter cachedWriter;
	private CharArrayWriter bufferedWriter;

	public ResponseWrapper(HttpServletResponse response) {
		super(response);
		// 这个是我们保存返回结果的地方
		bufferedWriter = new CharArrayWriter();
		// 这个是包装PrintWriter的，让所有结果通过这个PrintWriter写入到bufferedWriter中
		cachedWriter = new PrintWriter(bufferedWriter);
	}

	@Override
	public PrintWriter getWriter() {
		return cachedWriter;
	}

	/**
	 * 获取原始的HTML页面内容。
	 * 
	 * @return
	 */
	public String getResult() {
		return bufferedWriter.toString();
	}
}

public class EhcacheXcache implements Xcache {

	private Cache cache;

	public Cache getCache() {
		return cache;
	}

	public void setCache(Cache cache) {
		this.cache = cache;
	}

	public Object get(Object key) {
		Element e = (Element) cache.get(key);
		if (e != null) {
			return e.getValue();
		}
		return null;
	}

	public void set(String key, Object value) {
		Element e = new Element(key, value);
		cache.put(e);
	}

	@Override
	public String getName() {
		return cache.getName();
	}

}