public Customer validateCustomer(Customer customer) {

    //get the customer from the database
    Query q = em.createQuery("SELECT c from Customer c WHERE c.login = :username");
    q.setParameter("username", customer.getLogin());
    List<Customer> results = q.getResultList();

    //check if user exsists
    if(!results.isEmpty()){
       Customer fromDb = results.get(0);

       //check if user provided correct password
       if (!fromDb.getPassword().equals(customer.getPassword())) {
           return null;
       } else {
           //create the session token and save it to the database
           Random random = new SecureRandom();
           String token = new BigInteger(130, random).toString(32);
           tx.begin();
           int executeUpdate = em.createQuery("UPDATE Customer c SET c.token = :token WHERE c.id = :id")
                   .setParameter("token", token)
                   .setParameter("id", fromDb.getId())
                   .executeUpdate();
           tx.commit();
           em.close();

           //update previously pulled customer with the token
           fromDb.setToken(token);

           //return the customer
           return fromDb;
       }
    } else {
        return null;
    }
}

public Response login (Customer customer){
    Customer c = customerService.validateCustomer(customer);
    if (c != null){
        return Response.status(Response.Status.OK).entity(c).build();
        //System.out.println(c);
    } else {
        return Response.status(Response.Status.FORBIDDEN).entity("Incorrect username or password.").build();
    }
}

Customer c = new Customer();
           c.setEmail(fromDb.getEmail());
           c.setLogin(fromDb.getLogin());
           c.setToken(token);
           c.setId(fromDb.getId());