RestTemplate should be static globally declared?

Question

I am using Java Callable Future in my code. Below is my main code which uses the future and callables -

public class TimeoutThread {

    public static void main(String[] args) throws Exception {

        ExecutorService executor = Executors.newFixedThreadPool(5);
        Future<String> future = executor.submit(new Task());

        try {
            System.out.println("Started..");
            System.out.println(future.get(3, TimeUnit.SECONDS));
            System.out.println("Finished!");
        } catch (TimeoutException e) {
            System.out.println("Terminated!");
        }

        executor.shutdownNow();
    }
}

Below is my Task class which implements the Callable interface and I need to generate URL depending on the hostname we have and then make a call to SERVERS using RestTemplate. If there is any exception in the first hostname, then I will generate URL for another hostname and I will try making a call.

class Task implements Callable<String> {
    private static RestTemplate restTemplate = new RestTemplate();

    @Override
    public String call() throws Exception {

    //.. some code

    for(String hostname : hostnames)  {
            if(hostname == null) {
                continue;
            }
            try {
                String url = generateURL(hostname);         
                response = restTemplate.getForObject(url, String.class);

                // make a response and then break
                break;

            } catch (Exception ex) {
                ex.printStackTrace(); // use logger
            }
        }
    }
}

So my question should I declare RestTemplate as static global variable? Or it should not be static in this scenario?

Answer 1

It doesn't matter either way, static or instance.

RestTemplate's methods for making HTTP requests are thread safe so whether you have a RestTemplate instance per Task instance or a shared instance for all Task instances is irrelevant (except for garbage collection).

Personally, I would create the RestTemplate outside the Task class and pass it as an argument to a Task constructor. (Use Inversion of Control whenever possible.)