https://jersey.java.net/documentation/latest/async.html

AsyncResource.java

package com.example.app;

import java.util.Random;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.container.AsyncResponse;
import javax.ws.rs.container.Suspended;
import javax.ws.rs.core.Response;

@Path("/async")
public class AsyncResource {
	
	@GET
	public void asyncGet(@Suspended AsyncResponse asyncResponse) {
		new Thread(() -> {
			int sleepMillis = sleep();
			log("runnable thread end.(" + sleepMillis + ")");
			Response response = Response.ok("Success (" + sleepMillis + ")").build();
			asyncResponse.resume(response);
		}).start();

		log("server thread end.");
	}

	private int sleep() {
		try {
			int millis = new Random().nextInt(5) * 1000;
			Thread.sleep(millis);
			return millis;
		} catch (InterruptedException e) {
			throw new RuntimeException(e);
		}
	}

	private void log(String message) {
		System.out.println(message 
				+ " / " + Thread.currentThread().getId()
				+ " / " + Thread.currentThread().getName());
	}

}