public class GzipFilter2 implements Filter {
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        HttpServletResponse resp= (HttpServletResponse) response;
        //声明包装类对象
        MyResponse2 myresp = new MyResponse2(resp);
        //放行,调用oneServlet.doGet
        chain.doFilter(request, myresp);
        
        //第二步：从myresp2中读取原生的数据
        byte[] src = myresp.getSrc();
        
        //第三步：开始压缩
        ByteArrayOutputStream destBytes = new ByteArrayOutputStream();
        GZIPOutputStream zip = new GZIPOutputStream(destBytes);
        zip.write(src);
        zip.close();
        
        //第三步：输出-使用原生的response
        resp.setContentType("text/html;charset=UTF-8");
        //获压缩以后数据
        byte[] dest = destBytes.toByteArray();
        System.err.println("压缩之前："+src.length);
        System.err.println("压缩以后："+dest.length);
        //设置头
        resp.setContentLength(dest.length);
        resp.setHeader("Content-Encoding","gzip");
        //输出
        OutputStream out = resp.getOutputStream();
        out.write(dest);
        
    
    }
    public void destroy() {
    }

}

//第一步：声明response的包装类
class MyResponse2 extends HttpServletResponseWrapper{
    //将这个容器/a.txt,声明成员变量
    private ByteArrayOutputStream srcByte;
    private PrintWriter out; 
    public MyResponse2(HttpServletResponse response) {
        super(response);
    }
    //修改增强getWtier方法
    @Override
    public PrintWriter getWriter() throws IOException {
        srcByte = new ByteArrayOutputStream();
        out = 
                new PrintWriter(
                        new OutputStreamWriter(srcByte, "UTF-8"));
        return out;
    }
    //提供一个方法获取原生 的数据
    public byte[] getSrc(){
        if(out!=null){
            out.close();
        }
         return srcByte.toByteArray();
    }
}