java防止表单重复提交

  1 /**
  2  * 防重复提交工具类
  3  */
  4 public class TokenUtil {
  5     private static String REPEAT_SUBMIT_TOKEN = "REPEAT_SUBMIT_TOKEN";
  6     private static TokenUtil instance = new TokenUtil();
  7 
  8     private TokenUtil() {
  9 
 10     }
 11     
 12     public static TokenUtil getInstance() {
 13         return instance;
 14     }
 15 
 16     public static boolean isTokenValid(HttpServletRequest request) {
 17         return instance.isTokenValid(request, true);
 18     }
 19 
 20     public static boolean isTokenValid(HttpServletRequest request, boolean reset) {
 21         HttpSession session = request.getSession(false);
 22 
 23         if (session == null) {
 24             return false;
 25         }
 26 
 27         String saved = (String) session.getAttribute(REPEAT_SUBMIT_TOKEN);
 28 
 29         if (saved == null) {
 30             return false;
 31         }
 32 
 33         if (reset) {
 34             instance.resetToken(request);
 35         }
 36 
 37         String token = request.getParameter(REPEAT_SUBMIT_TOKEN);
 38 
 39         if (token == null) {
 40             return false;
 41         }
 42 
 43         return saved.equals(token);
 44     }
 45 
 46     public static void resetToken(HttpServletRequest request) {
 47         HttpSession session = request.getSession(false);
 48 
 49         if (session == null) {
 50             return;
 51         }
 52 
 53         session.removeAttribute(REPEAT_SUBMIT_TOKEN);
 54     }
 55 
 56     public static void saveToken(HttpServletRequest request) {
 57         HttpSession session = request.getSession();
 58         String token = instance.generateToken(request);
 59 
 60         if (token != null)
 61             session.setAttribute(REPEAT_SUBMIT_TOKEN, token);
 62     }
 63     
 64     public static void saveToken(HttpServletRequest request, ResponseJSON responseJSON) {
 65         HttpSession session = request.getSession();
 66         String token = instance.generateToken(request);
 67 
 68         if (token != null) {
 69             session.setAttribute(REPEAT_SUBMIT_TOKEN, token);
 70         }
 71         if (responseJSON != null) {
 72             responseJSON.setRepeatSubmitToken(token);
 73         }
 74             
 75     }
 76 
 77     private  String generateToken(HttpServletRequest request) {
 78         HttpSession session = request.getSession();
 79 
 80         return generateToken(session.getId());
 81     }
 82 
 83     private  String generateToken(String id) {
 84         try {
 85             long current = System.currentTimeMillis();
 86             current += new java.util.Random().nextInt(100);
 87 
 88             byte[] now = new Long(current).toString().getBytes();
 89             MessageDigest md = MessageDigest.getInstance("MD5");
 90 
 91             md.update(id.getBytes());
 92             md.update(now);
 93 
 94             return toHex(md.digest());
 95         } catch (NoSuchAlgorithmException e) {
 96         }
 97         return null;
 98     }
 99 
100     private  String toHex(byte[] buffer) {
101         StringBuffer sb = new StringBuffer(buffer.length * 2);
102 
103         for (int i = 0; i < buffer.length; i++) {
104             sb.append(Character.forDigit((buffer[i] & 0xF0) >> 4, 16));
105             sb.append(Character.forDigit(buffer[i] & 0xF, 16));
106         }
107 
108         return sb.toString();
109     }
110 }