Updating jsp variable inside of javascript

Question

I have a variable defined at the top of my jsp page:

<%! int count = 0; %>

I then call jquery with a buttonclick like so:

<script type="text/javascript">
$(document).ready(function() {         
    $('#somebutton').click(function() {
        var c = '<%=count%>';
        <% count += 5; %>
    });
});
</script>

The idea is that the variable count will be updated (and persist) after the function is done. However, it seems to update count locally but doesn't persist globally. When I click the button count always gets set to 5 but never increments to 10, 15, etc. upon further button clicks.

How can I update the jsp variable from within the jquery function and have it persist?

JSP is server-side. JavaScript is client-side. The two don't mix; what you're doing is incrementing it once. — Ry-
– Ry- ♦, Commented May 28, 2012 at 23:57
JSP produces HTML which get sent from webserver to webbrowser. JS is part of HTML. Rightclick page in browser and View Source to get enlightenend. — BalusC
– BalusC, Commented May 29, 2012 at 0:02
BalusC, I'm aware that pages are made up of HTML. Thanks, though. — Aaron
– Aaron, Commented May 29, 2012 at 0:06

SeanJA · Accepted Answer · 2012-05-29 00:03:06Z

1

You would have to do a call back to the server and store the data in a session variable (or cookie I suppose depending on the security needs).

answered May 29, 2012 at 0:03

SeanJA

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1 Comment

Aaron Over a year ago

For what I'm doing a cookie might suffice. Thanks for the idea.

Santino 'Sonny' Corleone · Accepted Answer · 2014-01-02 09:36:04Z

0

@Aaron-You can use one method in javascript like

function increment(){
                var value1=document.getElementById("lbl1").value;
                value1=parseInt(value1)+5;
                document.getElementById("lbl1").innerText=value1;
            }

where lbl1 is the id of the textbox in your jsp which has the initialized value as 0 i.e. <input type="text" value="<%=count%>" id="lbl1"/>. and on button click call increment() method like this <input type="submit" onclick="increment()"/>.

Hope this meets your requirements...

edited Jan 2, 2014 at 9:36

Santino 'Sonny' Corleone

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answered May 29, 2012 at 9:48

Ars

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2 Comments

Aaron Over a year ago

Nice idea, I ended up using a cookie but this is an interesting trick and would have probably also worked.

Ars Over a year ago

offcourse you can do with cookies also, but for this small requirement cookies methodology will be too lengthy...

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