java cookie 实现用户账号信息本地保存

package cn.itcast.util; 

 import java.io.IOException;  

import java.io.PrintWriter;  

import java.io.UnsupportedEncodingException;  

import javax.servlet.FilterChain;  

import javax.servlet.ServletException; 

 import javax.servlet.http.Cookie;  

import javax.servlet.http.HttpServletRequest; 

 import javax.servlet.http.HttpServletResponse; 

 import javax.servlet.http.HttpSession;  

import java.security.MessageDigest; 

 import java.security.NoSuchAlgorithmException;  

import cn.itcast.bean.User;  

import cn.itcast.dao.UserDAO; 

 import cn.itcast.factory.DaoImplFactory; 

 import com.sun.org.apache.xerces.internal.impl.dv.util.Base64; 

 /*  * 2007.09.21 by lyhapple  * */  

public class CookieUtil {         

//保存cookie时的cookieName        

 private final static String cookieDomainName = “cn.itcast”;                 

 //加密cookie时的网站自定码        

 private final static String webKey = “itcast”;          

 //设置cookie有效期是两个星期，根据需要自定义        

 private final static long cookieMaxAge = 60 * 60 * 24 * 7 * 2;                 

 //保存Cookie到客户端--------------------------------------------------------------------------------------------------------         //在CheckLogonServlet.java中被调用         

//传递进来的user对象中封装了在登陆时填写的用户名与密码         

public static void saveCookie(User user, HttpServletResponse response) {                               

 //cookie的有效期                

long validTime = System.currentTimeMillis() + (cookieMaxAge * 1000);                               

 //MD5加密用户详细信息               

 String cookieValueWithMd5 =getMD5(user.getUserName() + ":" + user.getPassword()                              + ":" + validTime + ":" + webKey);                              

  //将要被保存的完整的Cookie值               

 String cookieValue = user.getUserName() + ":" + validTime + ":" + cookieValueWithMd5;                               

 //再一次对Cookie的值进行BASE64编码                

String cookieValueBase64 = new String(Base64.encode(cookieValue.getBytes()));                              

  //开始保存Cookie               

 Cookie cookie = new Cookie(cookieDomainName, cookieValueBase64);               

 //存两年(这个值应该大于或等于validTime)  cookie.setMaxAge(60 * 60 * 24 * 365 * 2); 

 //cookie有效路径是网站根目录               

 cookie.setPath("/");               

 //向客户端写入               

 response.addCookie(cookie);       

  }                 

 //读取Cookie,自动完成登陆操作--------------------------------------------------------------------------------------------       

  //在Filter程序中调用该方法,见AutoLogonFilter.java        

 public static void readCookieAndLogon(HttpServletRequest request, HttpServletResponse response,  FilterChain chain) 

throws IOException, ServletException,UnsupportedEncodingException{                         

//根据cookieName取cookieValue  

Cookie cookies[] = request.getCookies();                      

 String cookieValue = null;                      

 if(cookies!=null){                            

  for(int i=0;i                                    

 if (cookieDomainName.equals(cookies[i].getName())) {                            

                cookieValue = cookies[i].getValue();                                 

           break;                                   

  }                              }                

       }                      

 //如果cookieValue为空,返回,                    

   if(cookieValue==null){                      

        return;            

           }                          

      //如果cookieValue不为空,才执行下面的代码             

   //先得到的CookieValue进行Base64解码             

   String cookieValueAfterDecode = new String (Base64.decode(cookieValue),"utf-8");       

                         //对解码后的值进行分拆,得到一个数组,如果数组长度不为3,就是非法登陆         

       String cookieValues[] = cookieValueAfterDecode.split(":");            

    if(cookieValues.length!=3){                  

     response.setContentType("text/html;charset=utf-8");                    

   PrintWriter out = response.getWriter();                      

 out.println("你正在用非正常方式进入本站...");                   

    out.close();                     

  return;            

    }                              

  //判断是否在有效期内,过期就删除Cookie         

       long validTimeInCookie = new Long(cookieValues[1]);          

      if(validTimeInCookie < System.currentTimeMillis()){                   

    //删除Cookie                      

 clearCookie(response);                   

    response.setContentType("text/html;charset=utf-8");         

              PrintWriter out = response.getWriter();           

            out.println("");你的Cookie已经失效,请重新登陆         

              out.close();              

         return;          

      }                          

      //取出cookie中的用户名,并到数据库中检查这个用户名,        

        String username = cookieValues[0];                  

              //根据用户名到数据库中检查用户是否存在       

         UserDAO ud = DaoImplFactory.getInstance();        

        User user = ud.selectUserByUsername(username);        

                        //如果user返回不为空,就取出密码,使用用户名+密码+有效时间+ webSiteKey进行MD5加密             

   if(user!=null){                       

String md5ValueInCookie = cookieValues[2];                      

 String md5ValueFromUser =getMD5(user.getUserName() + ":" + user.getPassword()                                     + ":" + validTimeInCookie + ":" + webKey);              

         //将结果与Cookie中的MD5码相比较,如果相同,写入Session,自动登陆成功,并继续用户请求               

        if(md5ValueFromUser.equals(md5ValueInCookie)){      

                        HttpSession session = request.getSession(true);    

                          session.setAttribute("user", user);                      

        chain.doFilter(request, response);                     

  }               

 }

else

{         

//返回为空执行                      

 response.setContentType("text/html;charset=utf-8");                

       PrintWriter out = response.getWriter();                  

     out.println("cookie验证错误！");                     

  out.close();       

  return;  

}      

   }               

   //用户注销时,清除Cookie,在需要时可随时调用------------------------------------------------------------        

 public static void clearCookie( HttpServletResponse response){                

Cookie cookie = new Cookie(cookieDomainName, null);              

  cookie.setMaxAge(0);               

 cookie.setPath("/");               

 response.addCookie(cookie);        

 }  

//获取Cookie组合字符串的MD5码的字符串----------------------------------------------------------------------------              

  public static String getMD5(String value) {                      

 String result = null;                      

 try{                          

    byte[] valueByte = value.getBytes();                    

          MessageDigest md = MessageDigest.getInstance("MD5");               

               md.update(valueByte);                         

     result = toHex(md.digest());                    

   } catch (NoSuchAlgorithmException e2)

{                             

 e1.printStackTrace();  

}                      

 return result;              

  }           

//将传递进来的字节数组转换成十六进制的字符串形式并返回            

    private static String toHex(byte[] buffer){                   

    StringBuffer sb = new StringBuffer(buffer.length * 2);            

           for (int i = 0; i < buffer.length; i++){                

              sb.append(Character.forDigit((buffer[i] & 0xf0) >> 4, 16));                         

     sb.append(Character.forDigit(buffer[i] & 0x0f, 16));                 

      }                  

     return sb.toString();          

      } 

 }