Basic Authentication Required Dialog
<?php
if (!isset($_SERVER['PHP_AUTH_USER'])) {
    header('WWW-Authenticate: Basic realm="My Realm"');
    header('HTTP/1.0 401 Unauthorized');
    echo 'Text to send if user hits Cancel button';
    exit;
} else {
    echo "<p>Hello {$_SERVER['PHP_AUTH_USER']}.</p>";
    echo "<p>You entered {$_SERVER['PHP_AUTH_PW']} as your password.</p>";
}
?>

<Directory /usr/local/apache/htdocs/secret>
    AuthType Basic
    AuthName "Restricted Files"
    # (Following line optional)
    AuthBasicProvider file
    AuthUserFile /usr/local/apache/passwd/passwords
    Require user rbowen
</Directory>

HttpServletResponse httpResponse = (HttpServletResponse) response;
httpResponse.setHeader("WWW-Authenticate", "Basic realm="My Realm"");
httpResponse.sendError(HttpServletResponse.SC_UNAUTHORIZED, "");

private boolean authenticateRequestOk(HttpServletRequest request)
{
    String authorizationHeader = request.getHeader("Authorization");

    if (authorizationHeader != null)
    {
        byte[] decodedUsernamePassword;
        try
        {
            decodedUsernamePassword = Base64.decode(authorizationHeader.substring("Basic ".length()));
        }
        catch (IOException e)
        {
            log.error("Error decoding authorization header "" + authorizationHeader + """, e);
            return false;
        }

        String usernameAndPassword = new String(decodedUsernamePassword);

        String username = StringUtils.substringBefore(usernameAndPassword, ":");
        String password = StringUtils.substringAfter(usernameAndPassword, ":");

        if (USERNAME.equalsIgnoreCase(username) && PASSWORD.equalsIgnoreCase(password))
        {
            return true;
        }
    }

    return false;
}