在网上找了半天也没找到相关的资料,都说的太含糊.
本人对tomcat下配置 一ip对多域名的方法详细如下,按下面配置一定能成功,经过测试了.

<Host name="localhost" debug="0" appBase="D:\\Tomcat 5.0\\webapps"
unpackWARs="true" autoDeploy="true"
xmlValidation="false" xmlNamespaceAware="false">
<Alias>localhost.com</Alias>
<Logger className="org.apache.catalina.logger.FileLogger"
directory="logs" prefix="localhost_log." suffix=".txt"
timestamp="true"/>
<Context path="" docBase="D:\\Tomcat 5.0\\webapps\\gg" reloadable="true" caseSensitive="false" debug="0"></Context>
</Host>

<Host name="one.localhost" debug="0" appBase="D:\\Tomcat 5.0\\webapps"
unpackWARs="true" autoDeploy="true"
xmlValidation="false" xmlNamespaceAware="false">
<Alias>one.localhost.com</Alias>
<Logger className="org.apache.catalina.logger.FileLogger"
directory="logs" prefix="localhost_log." suffix=".txt"
timestamp="true"/>
<Context path="" docBase="D:\\Tomcat 5.0\\webapps\\kk\\a" reloadable="true" caseSensitive="false" debug="0"></Context>
</Host>

<Host name="two.localhost" debug="0" appBase="D:\\Tomcat 5.0\\webapps"
unpackWARs="true" autoDeploy="true"
xmlValidation="false" xmlNamespaceAware="false">
<Alias>two.localhost.com</Alias>
<Logger className="org.apache.catalina.logger.FileLogger"
directory="logs" prefix="localhost_log." suffix=".txt"
timestamp="true"/>
<Context path="" docBase="D:\\Tomcat 5.0\\webapps\\kk\\b" reloadable="true" caseSensitive="false" debug="0"></Context>
</Host>

因无域名解析服务器,所以在hosts上配,来模拟dns解析.

10.1.1.241 localhost 指向gg文件夹
10.1.1.241 localhost.com 指向gg文件夹
10.1.1.241 one.localhost 指向a文件夹
10.1.1.241 one.localhost.com 指向a文件夹
10.1.1.241 two.localhost 指向b文件夹
10.1.1.241 two.localhost.com 指向b文件夹

经过多方面尝试,终于在tomcat下配置成功了.

修改默认的应用时：改defaulthost,并将context的path置为空。

配置多个应用时：

如：http://localhost:8080/

http://localhost:8080/first

http://localhost:8080/second

对应的配置如下：

<Host name="localhost" debug="0" appBase="D:\\Tomcat 5.0\\webapps"
unpackWARs="true" autoDeploy="true"
xmlValidation="false" xmlNamespaceAware="false">
<Alias>localhost.com</Alias>
<Logger className="org.apache.catalina.logger.FileLogger"
directory="logs" prefix="localhost_log." suffix=".txt"
timestamp="true"/>
<Context path="" docBase="D:\\Tomcat 5.0\\webapps\\Root" reloadable="true" caseSensitive="false" debug="0"></Context>

<Context path="/first" docBase="D:\\Tomcat 5.0\\webapps\\first" reloadable="true" caseSensitive="false" debug="0"></Context>
<Context path="/second" docBase="D:\\Tomcat 5.0\\webapps\\second" reloadable="true" caseSensitive="false" debug="0"></Context>
</Host>