看了网友Roy的评论，研究了一下用filter来解决Struts中文乱码的问题！

package tutorial.struts.filter;

import javax.servlet.Filter;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;
import javax.servlet.FilterChain;
import java.io.IOException;

public class SetCharacterEncodingFilter implements Filter {

  protected FilterConfig filterConfig;
  protected String encodingName;
  protected boolean enable;

  public SetCharacterEncodingFilter() {
    this.encodingName = "UTF-8";
    this.enable = false;
  }

  public void init(FilterConfig filterConfig) throws ServletException {
    this.filterConfig = filterConfig;
    loadConfigParams();
  }

  private void loadConfigParams() {
    //encoding     
    this.encodingName = this.filterConfig.getInitParameter("encoding");
    //filter enable flag
    String strIgnoreFlag = this.filterConfig.getInitParameter("enable");
    if (strIgnoreFlag.equalsIgnoreCase("true")) {
      this.enable = true;
    } else {
      this.enable = false;
    }
  }

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

  public void destroy() {
  }
		
}

  <filter>
     <filter-name>Set Character Encoding</filter-name>
     <filter-class>tutorial.struts.filter.SetCharacterEncodingFilter</filter-class>
     <init-param>
       <param-name>encoding</param-name>
       <param-value>UTF-8</param-value>
     </init-param>
     <init-param>
       <param-name>enable</param-name>
       <param-value>true</param-value>
     </init-param>
   </filter>
   <filter-mapping>
     <filter-name>Set Character Encoding</filter-name>
     <servlet-name>Action Servlet</servlet-name>
   </filter-mapping>
   <filter-mapping>
     <filter-name>Set Character Encoding</filter-name>
     <servlet-name>Faces Servlet</servlet-name>
   </filter-mapping>