Send a command without refreshing the page

I'm developing a web application using PlayFramework, and I'm having a problem clicking the command I would like to display an alert and not redirect the page as it is doing, redirecting to a blank screen. Instead, just show the alert that the command was sent and keep the current page on the screen.

My html page where I send the commands: where in the datatable I have the commands activate, deactivate and restart, these are the buttons where it is to send the command and only show an alert

<div class="panel-body">
    <ul class="list-group">
        <div class="col-lg-12">
            <div class="panel panel-default">
                <div class="panel-heading">
                    <h3 class="panel-title">
                        <i class="fa fa-cubes"></i> Detalhes Patch panels
                    </h3>
                </div>
                <div class="panel-body">
                    <div class="table-responsive">
                        <table class="table table-bordered table-hover table-striped">
                            <thead>
                                <tr>
                                    <th>Patch panel</th>
                                    <th>MAC</th>
                                    <th>IP</th>
                                    <th>Número de portas</th>
                                    <th>Status</th>
                                    <td></td>
                                </tr>
                            </thead>
                            <tbody>
                                #{list items:t.patchpanels, as:'p'}
                                <tr>
                                    <td>${p.nome}</td>
                                    <td>${p.mac}</td>
                                    <td>${p.ip}</td>
                                    <td>${p.numPortas}</td>
                                    <td>${p.status}</td>
                                    <td><center>
                                            <!-- Adicionado a função para enviar o comando do MQTT-->
                                            <!-- Adicionado a função para enviar o comando do MQTT -->
                                            <a href="@{comandosMqtt.ativar(p.ip, '0')}"><span class="btn btn-success btn-xs acaomqtt" > Ativar </span></a>
                                            <a href="@{comandosMqtt.reiniciar(p.ip, '0')}"><span class="btn btn-warning btn-xs acaomqtt" > Reiniciar </span></a> 
                                            <a href="@{comandosMqtt.desativar(p.ip, '0')}"><span class="btn btn-danger btn-xs acaomqtt"> Desativar </span></a>
                                            <a href="@{patchpanels.detalhesPatchpanel(p.id)}"><span class="btn btn-primary btn-xs"> Detalhes </span></a>
                                        </center></td>
                                </tr>
                                #{/list}
                            </tbody>


    </table>


    </div>
                </div>
            </div>
        </div>
    </ul>
</div>

When I click on the command button it the MQTT class:

public class ComandosMqtt extends Controller {
@AuditoriaOctopus
public static void ativar(String ip, String porta, String comando) throws MqttException {
    Mqtt mqtt = Mqtt.getInstance();

    mqtt.comandoMqtt(ip, porta, "active"); //envia os valores como parâmetro para a função
    //renderJSON("Ativado");//mostra apenas o IP na tela, é necessário alterar para poder mostrar novamente a página recarregada

}
@AuditoriaOctopus
public static void reiniciar(String ip, String porta, String comando) throws MqttException {
    Mqtt mqtt = Mqtt.getInstance();

    mqtt.comandoMqtt(ip, porta, "restart");
    //renderJSON("Reiniciado");
}
@AuditoriaOctopus
public static void desativar(String ip, String porta, String comando) throws MqttException {
    Mqtt mqtt = Mqtt.getInstance();

    mqtt.comandoMqtt(ip, porta, "deactive"); 
    //renderJSON("Desativado");
}

public ComandosMqtt(String ip, String porta) {
    try {
        Mqtt.getInstance();
    } catch (MqttException e) {
        e.printStackTrace();
    }
}

}