是缓存到tomcat里面去，所以就算换浏览器也是一样访问缓存，除非重启tomcat服务器才会重新访问网站

package cn.itcast.web.filter;import java.io.IOException;import java.util.HashMap;import java.util.Map;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.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import cn.itcast.web.decorator.MyResponse;//单例public class CacheFilter implements Filter {	//实例变量[每个线程共享]	private Map
    
      cache = new HashMap
     
      (); 		public void destroy() {	}	public void doFilter(ServletRequest req, ServletResponse res,FilterChain chain) throws IOException, ServletException {				HttpServletRequest request = (HttpServletRequest) req;		HttpServletResponse response = (HttpServletResponse) res;				//NO1：取得客户端访问的资源路径		String uri = request.getRequestURI();				//NO2：根据uri去缓存中查询对应的页面资源有没有		byte[] data = cache.get(uri);				//NO3：如果没有		if(data==null){			//将请求和响应放行到web资源中				MyResponse myResponse = new MyResponse(response);			chain.doFilter(request,myResponse);						//NO4:将刚取得的数据放入到缓存中，便于下次重用			data = myResponse.getBuffer();			cache.put(uri,data);						System.out.println("从服务端取得资源");					//NO5：如果有，直接从缓存中了得数据		}				//NO6：向浏览器输出数据		response.getOutputStream().write(data);	}	public void init(FilterConfig filterConfig) throws ServletException {	}}