How can I go through the servlet and apply css to the selected button?

<div id="schedulelist" class="list-group">
        <form id="my_form" method="POST" action="/SIST2_Travel/plan/planscd.do">
            <input type="submit" value="${"Day"} ${status.count} ${list}" class="btn btn-primary">
 
            <div class="d-flex w-100 align-items-center justify-content-between">
                <strong class="mb-1">${"Day"} ${status.count}</strong>
                <small>${list}</small>
            </div>

The code above is list.jsp. In this code, the tag takes you to planscd.do. And back to list.jsp again.

At this time, I want to change the class of the button of the clicked tag to btn-info.

How can I go through the servlet and apply css to the selected button?