How to convert JavaScript Variable to a JSP variable (int)

Question

I am trying to convert a javascript variable to a jsp variable like this

var correct=9;

<%int correct1%>=correct;

But it gives syntax error.

As far as I know, that's just not possible. At least not the way you want. — erikvimz
– erikvimz, Commented May 20, 2016 at 6:55
then what is the other method possible to achieve the target — zlareb1
– zlareb1, Commented May 20, 2016 at 6:57
You can allocate Java variables to Javascript to be run when the page is loaded but it can't go the other way around. If you wanted to pass a Javascript variable to JSP you'd have to make an Ajax request, open a new page or post a form. — erikvimz
– erikvimz, Commented May 20, 2016 at 7:00
this question has been answered many times, this is one of them stackoverflow.com/questions/8268356/… — Vibhesh Kaul
– Vibhesh Kaul, Commented May 20, 2016 at 7:03

Ali Mamedov · Accepted Answer · 2016-05-20 07:24:59Z

0

You can set a data in your JavaScript code from JSP, but not reverse. Something like this:

var correct = <% int correct1 = 1; out.println(correct1); %>;

If you want to transfer JavaScript variable's value to the server side, you have to do It only with form data posting or ajax.

Sample:

HTML file:

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script type="text/javascript">
    var correct = 9;

    $.ajax({

        url: 'your_jsp_file.jsp?correct=' + correct,
        method: 'get',
        success: function(result) {

            alert(result);
        }
    });
</script>

JSP file (your_jsp_file.jsp):

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%
    int correct1;

    if (request.getParameter("correct") == null) {

        out.println("error");
    } 
    else {

        String param = request.getParameter("correct");

        if (param.matches("^[0-9]+$")) {

            correct1 = Integer.parseInt(param);
        }

        out.println("ok");
    }
%>

edited May 20, 2016 at 7:24

answered May 20, 2016 at 6:59

Ali Mamedov

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5 Comments

erikvimz Over a year ago

Shouldn't out.println(correct) be out.println(correct1)?

erikvimz Over a year ago

Shouldn't 'your_jsp_file.jsp?correct' = correct be 'your_jsp_file.jsp?correct=' + correct

Ali Mamedov Over a year ago

@ErikKralj, thanks again :). I was so passionate about the process that did not pay attention to these errors

erikvimz Over a year ago

No problem, still missing an =. :D

Ali Mamedov Over a year ago

@ErikKralj, checkmate :)

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