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[Java教程]数据的压缩1 (52)


第四步:修改包装类Myresponse2,让输出数据放到一个内存缓存区中

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();  }}

第五步:全部的jsp都要经过压缩

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>

同时实现对getoutputstream和getWtier压缩

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;

    }