Java：Cookie實現記住用戶名、密碼

package com.gamecenter.api.util;

import java.io.IOException;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

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 com.gamecenter.api.common.UserInfo;


/** 
* 類說明 
* @author chitu
* @version 創建時間：2016年11月21日 下午1:39:51 
*/
public class CookieUtil {
    //保存cookie時的cookieName
    private final static String cookieDomainName = "gamecenter";
    //加密cookie時的網站自定碼
    private final static String webKey = "gamecenter";
    //設置cookie有效期是兩個星期，根據需要自定義
    private final static long cookieMaxAge = 60 * 60 * 24 * 7 * 2;
    //保存Cookie到客戶端-------------------------------------------------------------------------
    //在CheckLogonServlet.java中被調用
    //傳遞進來的user對象中封裝了在登陸時填寫的用戶名與密碼

    public static void saveCookie(String username,String password, HttpServletResponse response) throws Exception {
           //cookie的有效期
           long validTime = System.currentTimeMillis() + (cookieMaxAge * 5000);
           //MD5加密用戶詳細信息
           String cookieValueWithMd5 =getMD5(username + ":" + password+ ":" + validTime + ":" + webKey);
           //將要被保存的完整的Cookie值
           String cookieValue = username + ":" + validTime + ":" + cookieValueWithMd5;
           //再一次對Cookie的值進行BASE64編碼
           String cookieValueBase64 = new String(Base64Util.encode(cookieValue.getBytes()));
           //開始保存Cookie
           Cookie cookie = new Cookie(cookieDomainName, cookieValueBase64);
           //存兩年(這個值應該大於或等於validTime)
           cookie.setMaxAge(60 * 60 * 24 * 365 * 2);
           //cookie有效路徑是網站根目錄
           cookie.setPath("/");
           //向客戶端寫入
           response.addCookie(cookie);
    }

    //讀取Cookie,自動完成登陸操作----------------------------------------------------------------
    //在Filter程序中調用該方法,見AutoLogonFilter.java
    public static void readCookieAndLogon(HttpServletRequest request, HttpServletResponse response,FilterChain chain) throws IOException, ServletException,UnsupportedEncodingException{
    	//根據cookieName取cookieValue
    	Cookie cookies[] = request.getCookies();
        String cookieValue = null;
        if(cookies!=null){
             for(int i = 0; i < cookies.length; i++){
                    if (cookieDomainName.equals(cookies[i].getName())) {
                           cookieValue = cookies[i].getValue();
                           break;
                    }
             }
       }
       //如果cookieValue為空,返回,
       if(cookieValue==null){
             return;
       }
       //如果cookieValue不為空,才執行下面的代碼
       //先得到的CookieValue進行Base64解碼
       String cookieValueAfterDecode = new String (Base64Util.decode(cookieValue),"utf-8");
       //對解碼后的值進行分拆,得到一個數組,如果數組長度不為3,就是非法登陸
       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進入本站...");
              out.close();
              return;
       }
       //判斷是否在有效期內,過期就刪除Cookie
       long validTimeInCookie = new Long(cookieValues[1]);
       if(validTimeInCookie < System.currentTimeMillis()){
              //刪除Cookie
              clearCookie(response);
              response.setContentType("text/html;charset=utf-8");
              PrintWriter out = response.getWriter();
              out.println("你的Cookie已經失效,請重新登陸");
              out.close();
              return;
       }
       //取出cookie中的用戶名,並到數據庫中檢查這個用戶名,
       String username = cookieValues[0];
       //根據用戶名到數據庫中檢查用戶是否存在
       UserDAO ud = DaoImplFactory.getInstance();
       User user = ud.selectUserByUsername(username);
       //如果user返回不為空,就取出密碼,使用用戶名+密碼+有效時間+ webSiteKey進行MD5加密
       if(user!=null){
              String md5ValueInCookie = cookieValues[2];
              String md5ValueFromUser =getMD5(user.getUserName() + ":" + user.getPassword()
                            + ":" + validTimeInCookie + ":" + webKey);
              //將結果與Cookie中的MD5碼相比較,如果相同,寫入Session,自動登陸成功,並繼續用戶請求
              if(md5ValueFromUser.equals(md5ValueInCookie)){
                     HttpSession session = request.getSession(true);
                     session.setAttribute("user", user);
                     chain.doFilter(request, response);
              }
       }else{
       //返回為空執行
              response.setContentType("text/html;charset=utf-8");
              PrintWriter out = response.getWriter();
              out.println("cookie驗證錯誤！");
              out.close();
        return;

      }

    }

    

		//用戶注銷時,清除Cookie,在需要時可隨時調用-----------------------------------------------------
		public static void clearCookie( HttpServletResponse response){
		       Cookie cookie = new Cookie(cookieDomainName, null);
		       cookie.setMaxAge(0);
		       cookie.setPath("/");
		       response.addCookie(cookie);
		}

       //獲取Cookie組合字符串的MD5碼的字符串----------------------------------------------------------------
       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 e){
                     e.printStackTrace();
              }
              return result;
       }
       //將傳遞進來的字節數組轉換成十六進制的字符串形式並返回
       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();
       }
}