过滤器 + 过滤类解决乱码

WEB.XML:
<filter>
  <filter-name>encoding</filter-name>
  <filter-class>com.encodingfilter.EncodingFilter</filter-class>
  <init-param>
   <param-name>charset</param-name>
   <param-value>UTF-8</param-value>
  </init-param>
 </filter>
 <filter-mapping>
  <filter-name>encoding</filter-name>
  <url-pattern>/*</url-pattern>
 </filter-mapping>

CLASS:
package com.encodingfilter;

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 EncodingFilter implements Filter {

 private String charset = null;
 
 public void destroy() {
  // TODO Auto-generated method stub

 }

 public void doFilter(ServletRequest req, ServletResponse resp,
   FilterChain filter) throws IOException, ServletException {
  // TODO Auto-generated method stub
  req.setCharacterEncoding(this.charset);
  filter.doFilter(req, resp);
 }