//過濾器類
CharactorFilter.jsp
package cn.com.Filter;

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 CharactorFilter implements Filter { //繼承Filter類
    //字符編碼
    String encoding=null;

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        if(encoding!=null){
        //設置request字符編碼
            request.setCharacterEncoding(encoding);
         //設置response字符編碼
            response.setContentType("text/html;charset="+encoding);
        }
     //傳遞給下一個過濾器
        chain.doFilter(request, response);

    }

    public void init(FilterConfig filterConfig) throws ServletException {
      //獲取初始化參數
        encoding=filterConfig.getInitParameter("encoding");

    }

    public void destroy() {
        // TODO Auto-generated method stub
        encoding=null;
    }

}

 <filter>      <!--注意這里是filter，不要配置成servlet-->
    <filter-name>CharactorFilter</filter-name>    <!--過濾器名稱-->
   <filter-class>cn.com.Filter.CharactorFilter</filter-class>  <!--過濾器的完整類名--> 
     <init-param>   <!--初始化參數--> 
         <param-name>encoding</param-name>  <!--參數名稱--> 
         <param-value>utf-8</param-value>   <!--參數值--> 
     </init-param>
  </filter>
  <filter-mapping> <!--過濾器映射-->
      <filter-name>CharactorFilter</filter-name><!--過濾器名稱-->  
      <url-pattern>/*</url-pattern><!--URL映射，給所有頁面處理亂碼--> 
      </filter-mapping>