java—数据的压缩2 （52）

package cn.hongxin.filter;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;    public MyResponse2(HttpServletResponse response) {        super(response);    }    //修改增强getWtier方法    @Override    public PrintWriter getWriter() throws IOException {        srcByte = new ByteArrayOutputStream();        PrintWriter 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(){        return srcByte.toByteArray();    }}

只要是通过包装rersponse，且修改了getWriter方法，返回一个自己的printwiter对象。声明一个放原数据的容器对象。就可以实现数据压缩。

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();    }}

且它的配置如下：

<filter>

<filter-name>zip2</filter-name>

<filter-class>cn.itcast.filter.GzipFilter2</filter-class>

</filter>

<filter-mapping>

<filter-name>zip2</filter-name>

<url-pattern>*.jsp</url-pattern>

</filter-mapping>

在myrespons2这个类中，对getoutputstream也要覆盖。

返回一个ServletOutputSteam的匿名对象。

实现witer(int b)方法，将数据写到bytearrayoyutpoutstream.

public ServletOutputStream getOutputStream() throws IOException {

srcByte = new ByteArrayOutputStream();

ServletOutputStream out = new ServletOutputStream() {

//所有IO最终都是一个个字节写出信息

@Override

public void write(int b) throws IOException {

System.err.println(">>>:"+b);

srcByte.write(b);//写到自己的缓存中去-相当于StringBuffer.append(""+b);

}

};

return out;

}