解决的方法，就是在表单提交到ActionForm之前对request进行编码。
第一种方法，就是写一个过滤器，对所有请求进行过滤

过滤器代码:

package com.first.struts.filters;

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 SetCharacterEncodingFilter implements Filter {
 
 private String encoding;
 private FilterConfig filterConfig = null;
 
 public void destroy() {
  this.encoding = null;
  this.filterConfig = null;

 }

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

 public void init(FilterConfig filterConfig) throws ServletException {
  this.encoding = filterConfig.getInitParameter("encoding");
 }

}

配置文件web.xml

  <filter>
  <filter-name>Set Character Encoding</filter-name>
  <filter-class>com.first.struts.filters.SetCharacterEncodingFilter</filter-class>
  <init-param>
   <param-name>encoding</param-name>
   <param-value>GBK</param-value>
  </init-param>
 </filter>

 <filter-mapping>
  <filter-name>Set Character Encoding</filter-name>
  <url-pattern>/*</url-pattern>
 </filter-mapping>
  </filter-mapping>

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.ActionServlet;

public class SetEncodingActionServlet extends ActionServlet {
 protected void process(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
  // TODO Auto-generated method stub
  String encoding = getInitParameter("encoding");
  request.setCharacterEncoding(encoding);
  super.process(request, response);
 }
}

<servlet>
    <servlet-name>testAction</servlet-name>
    <servlet-class>jp.co.ricoh.gtis.others.profile.controllers.SetEncodingActionServlet</servlet-class>
    <init-param>
      <param-name>config</param-name>
      <param-value>/WEB-INF/struts-config.xml</param-value>
    </init-param>
    <init-param>
      <param-name>encoding</param-name>
      <param-value>Shift_JIS</param-value>
    </init-param>
    <load-on-startup>2</load-on-startup>
  </servlet>

  <servlet-mapping>
    <servlet-name>testAction</servlet-name>
    <url-pattern>*.testdo</url-pattern>
  </servlet-mapping>