IP过滤

/**
 *
 */
package com.ambow.servlet.day4;

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;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

//字符串解析
import java.util.StringTokenizer;

/**
 * 检查并阻塞特定的 IP
 * 阻止 192.168 开头的 ip 地址访问某个资源
 *
 * @author Administrator
 *
 */
public class Filter6 implements Filter {
 
 //指定要被屏蔽 的 ip
 private final static String IP_RANGE="192.168";
 
 /* (non-Javadoc)
  * @see javax.servlet.Filter#destroy()
  */
 public void destroy() {
  // TODO Auto-generated method stub

 }

 /* (non-Javadoc)
  * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)
  */
 public void doFilter(ServletRequest arg0, ServletResponse arg1,
   FilterChain arg2) throws IOException, ServletException {
  
  //转换 Request 对象
  HttpServletResponse res = null;
  
  //通过请求对象，得到客户端 ip 地址
  String ip = arg0.getRemoteAddr();
  System.out.println("客户端 ip ="+ip);
  
  if(arg1 instanceof HttpServletRequest)
  {
   res = (HttpServletResponse)arg1;
  }
  

  //将 ip 地址分解
  //127.0.0.1    ==>  127   0  0  1
  StringTokenizer toke = new StringTokenizer(ip,".");
  
  int dots = 0;
  String byte1="";
  String byte2="";
  String client="";
  
  while(toke.hasMoreTokens())
  {
   ++dots;
   
   //如果是第一个 ip
   if(dots == 1)
   {
    byte1 = toke.nextToken();
   }else {
    byte2 = toke.nextToken();
    
    //只关心前两个字节
    break;
   }
  }
  
  //将客户 ip 拼起来
  client = byte1+"."+byte2;
  
  //如果 ip 在被禁止的范围内
  if(this.IP_RANGE.equals(client))
  {
   System.out.println("该 ip 被禁止访问 :"+client);
   //403 禁止访问
   res.sendError(HttpServletResponse.SC_FORBIDDEN,"GoodBye Forever!");
  }else
  {
   System.out.println("该 ip 可以访问 :"+client);
   arg2.doFilter(arg0, arg1);
  }
  
  

 }

 /* (non-Javadoc)
  * @see javax.servlet.Filter#init(javax.servlet.FilterConfig)
  */
 public void init(FilterConfig arg0) throws ServletException {
  // TODO Auto-generated method stub

 }

}