一个简单的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;
/**
 * 采用Filter统一处理字符集
 * @author Administrator
 *
 */

public class CharsetEncodingFilter implements Filter {

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

 }

 public void doFilter(ServletRequest request, ServletResponse response,
   FilterChain chain) throws IOException, ServletException {
  
  //System.out.println("setCharacterEncodingFilter--->>begin");
  //设置字符集
  request.setCharacterEncoding(encoding);
  //继续执行
  chain.doFilter(request, response);
  //System.out.println("setCharacterEncodingFilter----->>end");
  
 }

//在tomcat启动时初始化

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

 }

}

//---------------------------------------------------------------------------------------------

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" 
 xmlns="http://java.sun.com/xml/ns/j2ee" 
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
 xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
 http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
  <!-- 
  <welcome-file-list>
 <welcome-file>index.html</welcome-file>
  </welcome-file-list>
   -->  <!-- 这段不要也可以，因为tomcat会自动找index.html index.jsp index.php 有默认值*/ -->
 
 <filter>
  <filter-name>CharsetEncodingFilter</filter-name>
  <filter-class>com.hugui.drp.util.filter.CharsetEncodingFilter</filter-class>
  <init-param>
   <param-name>encoding</param-name>
   <param-value>GBK</param-value>
  </init-param>
 </filter>
 <filter-mapping>
  <filter-name>CharsetEncodingFilter</filter-name>
  <url-pattern>*.jsp</url-pattern>
 </filter-mapping>
</web-app>