JAX-RS Client API async request - jax-rs

Question

I am trying to use the JAX-RS Client API to request a resource through HTTP GET, by using the following code: (I used jersey-client v2.12 and also resteasy-client v3.0.8.Final to test the implementation)
import javax.ws.rs.client.Client;
import javax.ws.rs.client.ClientBuilder;
import javax.ws.rs.client.InvocationCallback;
public class StackOverflowExample {
public static void main(String[] args) {
Client client = ClientBuilder.newClient();
client.target("http://example.com/").request().async().get(new InvocationCallback<String>() {
#Override
public void completed(String s) {
System.out.println("Async got: " + s);
}
#Override
public void failed(Throwable throwable) {
System.out.println("Async failure...");
}
});
}
}
As I expected the String is printed almost immediately. But the process keeps running about one minute, although there isn't any code that should be executed.
The JAX-RS spec just says that we should use the InvocationCallback and nothing else that matters to my issue. But even if I use a Future the same effect happens. I also tested, if this has something to do with a timeout, which was very unlikely and wrong. The debugger shows that there are some threads running namely DestroyJavaVM and jersey-client-async-executor-0 or pool-1-thread-1 in the case of resteasy.
Do you have any idea what is going wrong here?

Answer 1

It is allways helpful to consult the JavaDoc. Concerning my issue it says:
Clients are heavy-weight objects that manage the client-side communication infrastructure. Initialization as well as disposal of a Client instance may be a rather expensive operation. It is therefore advised to construct only a small number of Client instances in the application. Client instances must be properly closed before being disposed to avoid leaking resources.
If I close the client properly everything is working as expected.
public class StackOverflowExample {
public static void main(String[] args) {
Client client = ClientBuilder.newClient();
// request here
client.close();
}
}