这个其实是在web.xml文件中配置mime下载文件类型就可以了，配置的示例：
<mime-mapping> <extension>doc</extension> <mime-type>application/msword</mime-type> </mime-mapping> <mime-mapping> <extension>xls</extension> <mime-type>application/msexcel</mime-type> </mime-mapping> <mime-mapping> <extension>pdf</extension> <mime-type>application/pdf</mime-type> </mime-mapping> <mime-mapping> <extension>zip</extension> <mime-type>application/zip</mime-type> </mime-mapping> <mime-mapping> <extension>rar</extension> <mime-type>application/rar</mime-type> </mime-mapping> <mime-mapping> <extension>txt</extension> <mime-type>application/txt</mime-type> </mime-mapping> <mime-mapping> <extension>chm</extension> <mime-type>application/mshelp</mime-type> </mime-mapping>
这样就可以防止在浏览器是直接打开文件，而是弹出下载框供用户下载了。
原文：http://www.cnblogs.com/liangjq/p/4383469.html