JSP页面传值乱码过滤

1.过滤器类：

package com.token.t1;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class CharacterEncodingFilter implements Filter {

    public void destroy() {
    }

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
　　　　 request.setCharacterEncoding("gbk");
        chain.doFilter(request, response);
    }

    public void init(FilterConfig arg0) throws ServletException {
    }

}

2.xml文件配置：

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    
<!--过滤器配置-->
　　<filter>
        <filter-name>CharacterEncodingFilter</filter-name>     <!--此名字与<filter-mapping>下<filter-name>相同即可 -->
        <filter-class>com.token.t1.CharacterEncodingFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>CharacterEncodingFilter</filter-name>
        <url-pattern> /* </url-pattern>
    </filter-mapping>


    <display-name></display-name>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

当我用<form>的默认提交方式提交时，此方法过滤不了，需要设置 method="post"，才可以过滤