code: public static String hash(Serializable obj) {
  
  		if (obj == null) {
  			return "";
  		}
  		StringBuilder hexString = new StringBuilder();
  		try {
  
  			MessageDigest m = MessageDigest.getInstance("SHA1");
  			m.update(SerializationUtils.serialize(obj));
  
  			byte[] mdbytes = m.digest();
  
              for (byte mdbyte : mdbytes) {
                  hexString.append(Integer.toHexString(0xFF & mdbyte));
              }
  
  		} catch (NoSuchAlgorithmException e) {
  			return "";
  		}
  		return hexString.toString();
  	}
docs: Create a hash of a serializable object
  
  @param obj Serializable object
  @return Hash of the serializable object