public class RegisterRequest extends StringRequest {
    REGISTER_REQUEST_URL="http://192.168.8.237:8080/jbeefree/servletRegistraUsuario";
    //private static final String REGISTER_REQUEST_URL="http://64.137.182.149:8080/jbeefree/servletRegistraUsuario/";
    private Map<String, String> params;
    public RegisterRequest(String User, String Password, String Email, String Nombre, Response.Listener<String> listener){
        super(Method.GET, REGISTER_REQUEST_URL, listener, null);
        params = new HashMap<>();
        params.put("xUser", User);
        params.put("xPassword", Password);
        params.put("xEmail", Email);
        params.put("xNombre", Nombre);
        params.put("xPasswordmd5", String.valueOf(DigestUtils.md5(Password)));

    }


get the values on servlet:

        String xUser = request.getParameter("xUser");
        String xPassword = request.getParameter("xPassword");
        String xPasswordmd5 = request.getParameter("xPasswordmd5");
        String xEmail = request.getParameter("xEmail");
        String xNombre = request.getParameter("xNombre");


all values was null :(