Form submit for two times with null values and given me 500 error

Question

I created a login form which as I wanted to practice ajax from JQUERY. Unfortunately this program is given me unexpected error.

ISSUE Browser is given me 500 error : NullPointerException So I printed username and password. Then I saw that for one button click username and password print for two times and for first time it is same values as I entered and second time username is Null password is similar to entered value.And other thing is although I commented out the Ajax part that second scenario is happening (null username and entered password printing)

JSP:

<form action="" style="border:1px solid #ccc" method="post">
<div class="container">
  <h2>LogIn Form</h2>
    <label><b>Email</b></label>
    <input type="text" placeholder="Enter Email" name="email" id="uName" required>

    <label><b>Password</b></label>
    <input type="password" placeholder="Enter Password" name="psw" id="psw" required>

    <div class="clearfix">
      <button type="button" class="cancelbtn">Cancel</button>
      <button type="submit" class="signupbtn" id="login">LogIn</button>
    </div>
  </div>
</form>

JQUERY

<script type="text/javascript">
    $(document).ready(function() {
        alert("qwqw");
        $('#login').click(function(){
            $.post('userRegistrationServlet',{
                uName : $('#uName').val(),
                psw : $('#psw').val()},
                function(responseText) {
                    alert(uName);
                    alert("Login Successfully..!");
                });
        });
    });
</script>

Servlet

public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html");  
    //PrintWriter out = response.getWriter();

    String userName = request.getParameter("uName");
    System.out.println(userName+"uName");
    String psw = request.getParameter("psw");
    System.out.println(psw+"psw");
    RequestDispatcher rd;
    if(!userName.isEmpty()| userName != null){
    rd = request.getRequestDispatcher("/Header.html");
        rd.forward(request, response);
    }else{
        rd = request.getRequestDispatcher("/SignUp.jsp");
        rd.forward(request, response);
    }

}

public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws IOException, ServletException{
    request.getRequestDispatcher("UserRegistration.jsp").forward(request,response);
}

Please help me to solve this issue..Thank you..!

score 1 · Accepted Answer · answered Oct 03 '17 at 05:12

1

I'd rather put an event handler on the "submit" event of the form, then call preventDefault() and stopPropagation() on the event:

$("#myform").on("submit", function(e) {
    e.preventDefault();
    e.stopPropagation();
    $.post('userRegistrationServlet',{
            uName : $('#uName').val(),
            psw : $('#psw').val()},
            function(responseText) {
                alert(uName);
                alert("Login Successfully..!");
            });
});

answered Oct 03 '17 at 05:12

Maurice Perry

9,261
2
12
24

Thank you very much.yes these two functions are stopped submitting two times and my another fault was caught : I changed both name and id with the value uName for username filed then it is not given me null value for username filed. – user2490093 Oct 03 '17 at 05:31

score 0 · Answer 2 · answered Oct 03 '17 at 05:35

0

this button type is 'submit' so when you click it your form will be submit coherently but no url path LogIn

answered Oct 03 '17 at 05:35

Stone Wu

1
2

is that the reason for my issue? – user2490093 Oct 03 '17 at 06:23
i think so,you can try to change submit to button – Stone Wu Oct 03 '17 at 06:30
yes..It is correct form submitted only for one time by changing type submit to button – user2490093 Oct 03 '17 at 06:52

Form submit for two times with null values and given me 500 error

2 Answers2