Filter拦截器压缩全网站数据

创建拦截器类,需要实现javax.servlet.Filter接口

public class FilterDemo1 implements Filter {    @Override    public void init(FilterConfig arg0) throws ServletException {        System.out.println("服务器启动时调用此方法,只调用一次,用来初始化");    }    @Override    public void destroy() {        System.out.println("服务器退出时调用此方法,只调用一次");    }    @Override    public void doFilter(ServletRequest arg0, ServletResponse arg1,FilterChain chain) throws IOException, ServletException {        //转换Request,Response类型        HttpServletRequest request = (HttpServletRequest) arg0;        HttpServletResponse response =(HttpServletResponse) arg1;        //使用自定义Response,由自定义内部类实现        MyResponse response1 = new MyResponse(response);        //解除拦截        chain.doFilter(request1, response1);        //处理Response中的流数据        byte[] bytes = response1.getBytes();        System.out.println("压缩前的数据大小:"+bytes+"------"+bytes.length);        byte[] bytess = GZIPByte.getGzipByte(bytes);        System.out.println("压缩后的数据大小:"+bytess.length);        //设置Response返回数据类型,设置消息头        response.setHeader("Content-Encoding","gzip");        response.getOutputStream().write(bytess);    }}

自定义类继承HttpServletResponseWrapper类
注:HttpServletResponseWrapper类实现了HttpServletResponse接口

class MyResponse extends HttpServletResponseWrapper{        private HttpServletResponse response ;        public MyResponse(HttpServletResponse response) {            super(response);            this.response = response ;        }        private ByteArrayOutputStream baos = new ByteArrayOutputStream();        //此方法用来返回ByteArrayOutputStream中的底层数据        public byte[] getBytes(){            if(printWriter!=null){            //这里一定要flush(),因为printWriter里有缓冲区,如果缓冲区没有满,则不会将数据存入ByteArrayOutputStream底层流中                printWriter.flush();            }            return baos.toByteArray();        }        @Override        public ServletOutputStream getOutputStream() throws IOException {            //将数据不直接返回客户端,而是存入内存流            return new MyOutputStream(baos);        }        private PrintWriter printWriter = null;        @Override        public PrintWriter getWriter() throws IOException {            //利用OutputStreamWriter设置字符流的编码方式            printWriter = new PrintWriter(new OutputStreamWriter(baos,"utf-8"));             //将数据不直接返回客户端,而是存入内存流            return printWriter;        }    }

自定义内部类继承ServletOutputStream

class MyOutputStream extends ServletOutputStream{        private ByteArrayOutputStream baos;        public MyOutputStream(ByteArrayOutputStream baos){            this.baos = baos;         }        @Override        public void write(byte[] b, int off, int len) throws IOException {            baos.write(b, off, len);        }        @Override        public void write(byte[] b) throws IOException {            baos.write(b);        }        @Override        public void write(int b) throws IOException {            baos.write(b);        }    }

Util包中的GZIPByte工具类,用来压缩数据

public static byte[] getGzipByte(byte[] bs){        //定义一个内存流        ByteArrayOutputStream baos = new ByteArrayOutputStream();        try {            //定义一个GZIP压缩流,参数为内存流,将压缩到的数据存入底层的内存流            GZIPOutputStream gos = new GZIPOutputStream(baos);            gos.write(bs);            gos.close();        } catch (IOException e) {            throw new RuntimeException(e);        }        //返回压缩后的字节数据        return baos.toByteArray();    }

在web.xml中配置拦截器

    <filter>        <filter-name>FilterDemo1</filter-name>        <filter-class>filter.demo.FilterDemo1</filter-class>    </filter>    <filter-mapping>        <filter-name>FilterDemo1</filter-name>        <!-- 拦截所有 -->        <url-pattern>/*</url-pattern>    </filter-mapping>