Servlet编码过滤器的实现
1 编写过滤器类 encodingfilter

<filter><filter-name>encoding</filter-name><filter-class>test.encodingfilter</filter-class><init-param><param-name>charset</param-name><param-value>gbk</param-value></init-param></filter><filter-mapping><filter-name>encoding</filter-name><url-pattern>/*</url-pattern></filter-mapping>