Session learning: prevents users from submitting forms repeatedly (single-State Design Mode-atomic design mode + MD5 Technology & amp; Base64 algorithm)

1. FormServlet. java designs a form to submit data to prevent users from repeatedly submitting data to the server. The blocking code is as follows:

FormServlet "text/html; charset = UTF-8" = "token", token ); "<form action = '/day07/servlet/DoFormServlet' method = 'post'>" "<input type = 'den den 'name = 'Token' value ='" + token + "'>" "User Name: <input type = 'text' name = 'username'> "" <input type = 'submit 'value = 'Submit'> "" </form> "TokenProccessor {TokenProccessor instance = string makeToken () {String token = (System. currentTimeMillis () + Random (). nextInt (999999999) + "" = MessageDigest. getInstance ("md5" md5 [] = BASE64Encoder encoder =

2. DoFormServlet. java implements the function of preventing repeated data submission on the client and server respectively. The Code is as follows:

DoFormServlet B = isToken (request); (B = "Please do not submit" "token" "again to process user submitted requests !! "= Request. getParameter (" token "(client_token =) {= (String) request. getSession (). getAttribute (" token "(server_token = ){(! Client_token.equals (server_token )){