Ajax verifies that the verification code entered by the user is consistent with the randomly generated one

Background Java code [Captcha generation]

/**
 *  Randomly generated 6 Bit random verification code 
 */
 public static String createRandomVcode(){
 // Verification code 
 String vcode = "";
 for (int i = 0; i < 6; i++) {
  vcode = vcode + (int)(Math.random() * 9);
 }
 return vcode;
 }

Background Java code [Use captchAs and save them in session]

String authCode = xioo.createRandomVcode(); // Generate captcha randomly 
HttpSession session=request.getSession();  //session attribute 
session.setAttribute("authCode", authCode); //  Save the captcha to session inside 

Background Java code [Compare the verification code entered by the user with the verification code in session]

HttpSession session=request.getSession();
 String usercode=request.getParameter("user_code"); // Gets the verification code entered by the user 
 String sessioncode=(String) session.getAttribute("authCode"); // Get saved in session The captcha inside 
 String result="";
 if( usercode != null && usercode.equals(sessioncode)){ // Compare the two code Whether it is right 
  result = "1";
 }else{
  result = "0";
 }
 PrintWriter out = response.getWriter();
 out.write(result.toString()); // Send the data to the front desk 
 }

Foreground Ajax code [To obtain user input code and send it to the background]

$(document).ready(function() {
 $("#user_code").blur(function() {
 var user_code = $("#user_code").val(); //ur The event 
 //  Sends processing data to the background  
 $.ajax({
  url : "CheckCode", // The target address 
  data : "user_code=" + user_code, // Transmitted data 
  type : "POST", //  with POST Way to transport  
  dataType : "text", //  The data format 
  success : function(data) {
  data = parseInt(data, 10);
  if (data == 1) {
   $("#error").html("<font color='#339933'> Square root   The SMS verification code is correct, please continue </font>");
  } else if (data == 0){
   $("#error").html("<font color='red'> x   Verification code is wrong, please fill in again after verification </font>");
  }
  }
 });
 });
});

<input type="text" name="user_code" id="user_code" placeholder="请输入验证码"/>