过滤器压缩全站jsp

过滤器：

public class Gzip implements Filter {

    public void destroy() {}

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        HttpServletResponse resp=(HttpServletResponse) response;
        MyResp myResp=new MyResp(resp);//包装过的response
        chain.doFilter(request, myResp);//放行
        
        byte[] srcBytes= myResp.getSrcByte();//获取源数据
        ByteArrayOutputStream bOutStream=new ByteArrayOutputStream();//目标容器
        GZIPOutputStream zipOutStream=new GZIPOutputStream(bOutStream);//压缩工具
        zipOutStream.write(srcBytes);//写到容器中
        zipOutStream.close();//如果不关闭，会在缓存中，不写出
        
        byte[] descByte=bOutStream.toByteArray();
        
        System.out.println("-------------------");
        System.out.println("压缩前："+srcBytes.length);
        System.out.println("压缩后："+ descByte.length);
        System.out.println("-------------------");
        
        //使用原生response输出
        resp.setContentType("text/html;charset=utf-8");
        resp.setHeader("Content-Encoding", "Gzip");
        resp.setContentLength(srcBytes.length);
        
        //输出
        OutputStream out=resp.getOutputStream();
        out.write(descByte);//关闭
        
        
    }
    public void init(FilterConfig filterConfig) throws ServletException {}

}

class MyResp extends HttpServletResponseWrapper
{
    private  PrintWriter outWrite;
    private ByteArrayOutputStream srcByte;
    //获取原生数据
    public byte[] getSrcByte() {
        if(outWrite!=null)//如果不关闭流，不会显示，因为数据在缓存中，没有写出
        {
            outWrite.close();
        }
        return srcByte.toByteArray();
    }

    public MyResp(HttpServletResponse response) {
        super(response);

    }

    //包装getWrite()方法，jsp页面输出内容使用的是response.getWriter().write（""）
    //所以要包装
    @Override
    public PrintWriter getWriter() throws IOException {
        srcByte=new ByteArrayOutputStream();//输出的源数据
        outWrite=new PrintWriter(new OutputStreamWriter(srcByte,"utf-8"));        
        return outWrite;
    }
    
}

如果过滤器需要过滤Servlet，则需要用response.getWriter().write（""）输出，否则不会被过滤

response.setContentType("text/html;charset=utf-8");    
        String str="你好，同学；Hello World";
        PrintWriter writer=response.getWriter();
        writer.write(str);
        writer.close();

如果Servlet中使用response.getOutputStream().write("")输出，则需要包装getOutputStream()方法

response.setContentType("text/html;charset=utf-8");    
        String str="你好，同学；Hello World";
        String times=request.getParameter("times");
        int n=Integer.valueOf(times);
        OutputStream out=response.getOutputStream();
        for (int i = 0; i < n; i++) {
            out.write(str.getBytes("utf-8"));
        }
        out.close();

包装getOutputStream()方法

    @Override
    public ServletOutputStream getOutputStream() throws IOException {
        srcByte =new ByteArrayOutputStream();//输出的源数据
        ServletOutputStream out=new ServletOutputStream() {            
            @Override
            public void write(int b) throws IOException {
                srcByte.write(b);                
            }
        };
        return out;
    }