JSP Page showing previous session data

I created a login form in jsp. Also made the session save system that when the user will log in his username will be visible in the welcome page inside a label tag. I used this code for this -

In the login page :

request.getSession().setAttribute("username",username);

And in the welcome page :

out.print(request.getSession().getAttribute("username"));

Also have an log out link like anchor tag which's href="/login.jsp"

Now I comes to the problem. When I first time login with the username "a" it successfully shows "a" in the welcome page. But when I logout and login again with username "b" then also it shows "a" in the welcome page. When I refresh the browser then it shows "b". I can try a method that I can make a code that will refresh the browser after first refresh. But my page will be too heavy in future. For that this will be not a standard way right?

I found a solution that session.invalidate(); but I tried this code inside anchor tag but is of no use.

Kindly help!

Here is the logout page code -

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <link rel="stylesheet" type="text/css" href="css/style.css">
    <script type="text/javascript" src="js/basic.js"></script>
    <title>Dashboard || XCEL-ERP</title>
</head>
<body>
    <div class="dashboard_sidebar" id="dashboard_sidebar">
        <ul>
            <li class="sidebar_item"><a href="#">HOME</a></li>
            <li class="sidebar_item"><a href="#">RECIPE & COSTING</a></li>
            <li class="sidebar_item"><a href="#">PLANNING</a></li>
            <li class="sidebar_item"><a href="#">PRODUCTION</a></li>
            <li class="sidebar_item"><a href="#">ACCOUNT</a></li>
            <li class="sidebar_item"><a href="#">OVERVIEW</a></li>
        </ul>
    </div>
    <div class="dashboard_header" id="dashboard_header">
        <div class="dashboard_hamburger" onclick="sidebarFunction()">
            <span></span>
            <span></span>
            <span></span>
        </div>
        <div class="logo">ERP</div>
        <div class="user">
            <img src="https://www.dropbox.com/s/s3wcx1zot0gp3fe/user_icon.png?raw=1" alt="user" onclick="userProfileFunction()">
            <label>
             <%  

                out.print(request.getSession().getAttribute("username"));

             %>
             </label>
             <div class="userProfileBox" id="userProfileBox">
                <img src="https://www.dropbox.com/s/zq3d2dz63y3y4ct/man_pic.jpg?raw=1" alt="Profile_img">
                <div class="userName"> <% out.print(request.getSession().getAttribute("username")); %> </div>
                <div class="desg_Section"> Costing Officer - Wash </div>
                <div class="authorization">User has authorization of : </div>
                <button>Log Out</button>
             </div>
        </div>
        <a href="login.jsp">Log Out</a>
    </div>
</body>
</html>

And here is the login connection code which is connected to a form method post -

<%@ page import = "java.sql.*"%>
<%

    String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    String DB_URL = "jdbc:mysql://localhost:3306/erp";
    String DB_USER = "root";
    String DB_PASS = "";

    Connection conn = null;
    Statement stm = null;
    ResultSet rs = null;

    String username = request.getParameter("username");
    String password = request.getParameter("password");

    String query = "SELECT * FROM userdata WHERE UserName = '".concat(username).concat("' AND Password = '").concat(password).concat("'");

    try{
        Class.forName(JDBC_DRIVER);
        conn = DriverManager.getConnection(DB_URL, DB_USER, DB_PASS);
        stm = conn.createStatement();

        rs = stm.executeQuery(query);

        Boolean match_result = rs.isBeforeFirst();

        if(match_result == true){

            getServletContext().getRequestDispatcher("/dashboard.jsp").forward(request, response);

            
            request.getSession().setAttribute("username",username);

        }else{

            out.print("Sorry, username or password error!");  
            request.getRequestDispatcher("/login.jsp").forward(request, response);
            
        }

        rs.close();
        stm.close();
        conn.close();
    } catch(Exception e){
        out.println(e);
    }

%>