getAsyncContext() : Gets the AsyncContext

public AsyncContext getAsyncContext()

Gets the AsyncContext that was created or reinitialized by the most recent invocation of startAsync() or startAsync(ServletRequest,ServletResponse) on this request.

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.AsyncContext;

@WebServlet(urlPatterns = {"/ProcessRequest"}, asyncSupported=true)
public class ProcessRequest extends HttpServlet {
    @Override
    public void doGet(HttpServletRequest req, HttpServletResponse res)throws IOException, ServletException{
            req.startAsync();
            final AsyncContext acontext = req.getAsyncContext();
            String threadName = Thread.currentThread().getName();
            long startTime = System.currentTimeMillis();
            System.out.println("Thread " + threadName + " started at " + startTime);

            acontext.start(new Runnable() {

                public void run() {
                    String time = req.getParameter("time");
                    int wait = Integer.parseInt(time);
                    
                    try{
                        Thread.sleep(wait);
                    }
                    catch(InterruptedException e){
                        
                    }
                    HttpServletResponse response = (HttpServletResponse)acontext.getResponse();
                    try(PrintWriter out = response.getWriter()) {
                        out.println("I am done");
                    }
                    catch(Exception e){
                        
                    }
                    acontext.complete();
                }
            });
            
            long endTime = System.currentTimeMillis();
            System.out.println("Thread " + threadName + " finished at " + endTime);
            System.out.println("Total time taken is " +(endTime-startTime) + " Milli Seconds");
       
    }
}

Run the above servlet like below.

http://localhost:8080/servlet/ProcessRequest?time=10000

As you see the console logs, you can observe the below information messages immediately.

Info: Thread http-listener-1(5) started at 1405140693455

Info: Thread http-listener-1(5) finished at 1405140693456

Info: Total time taken is 1 Milli Seconds

After 10 seconds you can see the response in your browser.

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