@Async("threadPoolTaskExecutorForSMS")
    public void sendSMS(String phoneNumber, String content) {
        try {
            final String uri = "http://bulksms.teletalk.com.bd/link_sms_send.php?op=SMS&user=grs_user&pass=b@LYu4sM&mobile=" +
                    phoneNumber +
                    "&charset=UTF-8&sms=" +
                    content;

            RestTemplate restTemplate = new RestTemplate();
            String result = restTemplate.getForObject(uri, String.class);
            log.info("SMS Sent at: " + phoneNumber);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

----------------------------------------------------------------
write this in a class that has @configuration annotation
----------------------------------------------------------------
@Bean(name = "threadPoolTaskExecutorForSMS")
    public Executor threadPoolTaskExecutorForShortMessageService() {
        return new ThreadPoolTaskExecutor();
    }