文本压缩过滤器实现

package com.tinysoft.cn;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.OutputStreamWriter;import java.io.PrintWriter;import java.util.zip.GZIPOutputStream;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpServletResponseWrapper;/** *  * @author 董乐强 2017-7-30 文本压缩过滤器的实现 */public class GzipFilter implements Filter {public void init(FilterConfig filterConfig) throws ServletException {}public void doFilter(ServletRequest req, ServletResponse resp,FilterChain chain) throws IOException, ServletException {// TODO Auto-generated method stubHttpServletRequest request;HttpServletResponse response;try {request = (HttpServletRequest) req;response = (HttpServletResponse) resp;} catch (Exception e) {throw new RuntimeException("non-http request");}// 要对响应到，浏览器的数据进行压缩，则必须获得拦截到响应到浏览器的数据// 所以必须对response进行包装，然后将返回的数据保存到内存流中，进行缓存// 从而我们可以从内存流中截取response封装的数据，燃后进行压缩处理之后，返回给浏览器MyHttpServletResponse myresponse = new MyHttpServletResponse(response);// 我要拦截response对象，则在放行之后，进行拦截chain.doFilter(request, myresponse);// 要对响应到，浏览器的数据进行压缩，则必须获得拦截到响应到浏览器的数据// 所以必须对response进行包装，才可以byte b[] = myresponse.getBytes();System.out.println("压缩前大小:" + b.length);// 将数据压缩到内存流中去ByteArrayOutputStream out = new ByteArrayOutputStream();GZIPOutputStream gout = new GZIPOutputStream(out);gout.write(b);gout.close();// 从内存流中去压缩数据b = out.toByteArray();System.out.println("压缩后大小：" + b.length);// 通知浏览器正文的压缩格式response.setHeader("Content-Encoding", "gzip");// 将压缩后的数据写回到浏览器response.getOutputStream().write(b);}public void destroy() {// TODO Auto-generated method stub}}class MyHttpServletResponse extends HttpServletResponseWrapper {private HttpServletResponse response;// 将response输出到浏览器的数据，先保存到内存流中就行缓存private ByteArrayOutputStream baos = new ByteArrayOutputStream();// 字符输出流private PrintWriter pw;public MyHttpServletResponse(HttpServletResponse response) {super(response);this.response = response;}@Overridepublic ServletOutputStream getOutputStream() throws IOException {return new MyServletOutputStream(baos);}@Overridepublic PrintWriter getWriter() throws IOException {pw = new PrintWriter(new OutputStreamWriter(baos,response.getCharacterEncoding()));return pw;}// 将内存流输出，得到结果public byte[] getBytes() {try {if (pw != null)pw.close();baos.flush();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}return baos.toByteArray();}}// 在一次进行包装，将数据写到内存流中class MyServletOutputStream extends ServletOutputStream {private ByteArrayOutputStream baos;public MyServletOutputStream(ByteArrayOutputStream baos) {this.baos = baos;}@Overridepublic void write(int b) throws IOException {// 写到内存流中去baos.write(b);}}