实      现：　　

Tomcat 开启Gzip ：

1.找到Tomcat 目录下的conf下的server.xml，并找到如下信息

将它改成如下的形式（其实在上面代码的下面已经有了，将他们打开而已。）：

这样，就能够对html和xml进行压缩了，如果要压缩css 和 js，那么需要将

compressableMimeType=”text/html,text/xml”加入css和js：

你甚至可以压缩图片：

compressableMimeType=”text/html,text/xml”加入css和js：

开启后重启Tomcat ，通过浏览器查看headers信息就能看到是否开启（firebug中有），如果开启了，那么transfer-encoding就会是Gzip，否则就是chunked。

 

在代码级别完成web应用的gzip压缩的开启：

 

1.Wrapper  用来包装HttpServletResponse 对象 

package com.shop.gzip;

import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.OutputStreamWriter; import java.io.PrintWriter; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpServletResponseWrapper; public class Wrapper extends HttpServletResponseWrapper {     public static final int OT_NONE = 0, OT_WRITER = 1, OT_STREAM = 2;     private int outputType = OT_NONE;     private ServletOutputStream output = null;     private PrintWriter writer = null;     private ByteArrayOutputStream buffer = null;     public Wrapper(HttpServletResponse resp) throws IOException {         super(resp);         buffer = new ByteArrayOutputStream();     }     public PrintWriter getWriter() throws IOException {         if (outputType == OT_STREAM)             throw new IllegalStateException();         else if (outputType == OT_WRITER)             return writer;         else {             outputType = OT_WRITER;             writer = new PrintWriter(new OutputStreamWriter(buffer,                     getCharacterEncoding()));             return writer;         }     }     public ServletOutputStream getOutputStream() throws IOException {         if (outputType == OT_WRITER)             throw new IllegalStateException();         else if (outputType == OT_STREAM)             return output;         else {             outputType = OT_STREAM;             output = new WrappedOutputStream(buffer);             return output;         }     }     public void flushBuffer() throws IOException {         if (outputType == OT_WRITER)             writer.flush();         if (outputType == OT_STREAM)             output.flush();     }     public void reset() {         outputType = OT_NONE;         buffer.reset();     }     public byte[] getResponseData() throws IOException {         flushBuffer();         return buffer.toByteArray();     }     class WrappedOutputStream extends ServletOutputStream {         private ByteArrayOutputStream buffer;         public WrappedOutputStream(ByteArrayOutputStream buffer) {             this.buffer = buffer;         }         public void write(int b) throws IOException {             buffer.write(b);         }         public byte[] toByteArray() {             return buffer.toByteArray();         }     } }

 

 

2.过滤器

 

 

 package com.shop.gzip;

import java.io.ByteArrayOutputStream; import java.io.IOException; 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; public class GZipFilter implements Filter {     public void destroy() {     }       /**        * 判断浏览器是否支持GZIP        * @param request        *        */       private static boolean isGZipEncoding(HttpServletRequest request){         boolean flag=false;         String encoding=request.getHeader("Accept-Encoding");         if(encoding.indexOf("gzip")!=-1){           flag=true;         }         return flag;       }            public void doFilter(ServletRequest request, ServletResponse response,             FilterChain chain) throws IOException, ServletException {         HttpServletResponse resp = (HttpServletResponse) response;         HttpServletRequest req=(HttpServletRequest)request;         if(isGZipEncoding(req)){             Wrapper wrapper = new Wrapper(resp);             chain.doFilter(request, wrapper);             byte[] gzipData = gzip(wrapper.getResponseData());             resp.addHeader("Content-Encoding", "gzip");             resp.setContentLength(gzipData.length);             ServletOutputStream output = response.getOutputStream();             output.write(gzipData);             output.flush();         } else {             chain.doFilter(request, response);         }             }     public void init(FilterConfig arg0) throws ServletException {     }     private byte[] gzip(byte[] data) {         ByteArrayOutputStream byteOutput = new ByteArrayOutputStream(10240);         GZIPOutputStream output = null;         try {             output = new GZIPOutputStream(byteOutput);             output.write(data);         } catch (IOException e) {         } finally {             try {                 output.close();             } catch (IOException e) {             }         }         return byteOutput.toByteArray();     } }

3.在web.xml中配置 GZipFilter,当我们访问应用中以.do结尾的资源的使用,服务器端就开启http gzip压缩,将压缩后的信息通过http 协议传递给浏览器.  

  

<filter>  

　　<filter-name>ecsideExport</filter-name>  

　　<filter-class>com.web.servlet.GZipFilter</filter-class>  

 </filter>  

<filter-mapping>  

             <filter-name>ecsideExport</filter-name>  

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

</filter-mapping>