背景：
HTTP 壓縮可以大大提高瀏覽網站的速度，它的原理是，在客戶端請求網頁后，從服務器端將網頁文件壓縮，再下載到客戶端，由客戶端的瀏覽器負責解壓縮并瀏覽。相對于普通的瀏覽過程HTML ,CSS,Javascript , Text ，它可以節省40%左右的流量。更為重要的是，它可以對動態生成的，包括CGI、PHP , JSP , ASP , Servlet,SHTML等輸出的網頁也能進行壓縮，壓縮效率驚人

一，對于Tomcat5.0以后的版本是支持對輸出內容進行壓縮的.　使用的是gzip壓縮格式

下面是tomcat5.5.20 中的$tomcat_home$/conf/server.xml的原內容

1      < Connector port ="80" maxHttpHeaderSize ="8192"
2                 maxThreads ="150" minSpareThreads ="25" maxSpareThreads ="75"
3                 enableLookups ="false" redirectPort ="8443" acceptCount ="100"
4                 connectionTimeout ="20000" disableUploadTimeout ="true" URIEncoding ="utf-8" />
5      <!-- Note : To disable connection timeouts, set connectionTimeout value
6       to 0 -->
7     
8      <!-- Note : To use gzip compression you could set the following properties :
9     
10                 compression="on"
11                 compressionMinSize="2048"
12                 noCompressionUserAgents="gozilla, traviata"
13                 compressableMimeType="text/html,text/xml"
14      -->

1    <Connector port="80" maxHttpHeaderSize="8192"
2                maxThreads="150" minSpareThreads="25" maxSpareThreads="75"
3                enableLookups="false" redirectPort="8443" acceptCount="100"
4                connectionTimeout="20000" disableUploadTimeout="true" URIEncoding="utf-8"
5                   compression="on"
6                compressionMinSize="2048"
7                noCompressionUserAgents="gozilla, traviata"
8                compressableMimeType="text/html,text/xml,text/javascript,text/css,text/plain"  />
9    <!-- Note : To disable connection timeouts, set connectionTimeout value
10      to 0 -->
11    
12    <!-- Note : To use gzip compression you could set the following properties :
13    
14                compression="on"
15                compressionMinSize="2048"
16                noCompressionUserAgents="gozilla, traviata"
17                compressableMimeType="text/html,text/xml"
18    -->
19