解决办法:
将tomcat安装目录的conf目录下的servlet.xml的
<Connector port="8080" protocol="HTTP/1.1"
connectionTimeout="20000"
redirectPort="8443" />
改为
<Connector port="8080" protocol="HTTP/1.1"
connectionTimeout="20000"
redirectPort="8443" URIEncoding="gbk" />
(即,添加URIEncoding="gbk"到Connector元素中)