ServletRequest执行startAsync()或者startAsync(ServletRequest, ServletResponse) 进入异步模式，将会创建一个AsyncContext，将其需要异步的操作放在此AsyncContext中
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addListener(AsyncListener?listener)//可以增加监听器
startAsync()
startAsync(ServletRequest, ServletResponse)
将当前请求/响应 或指定请求/响应 放到异步模式中
void
onComplete(AsyncEvent?event)
??????????Notifies this AsyncListener that an asynchronous operation has been completed.
?void
onError(AsyncEvent?event)
??????????Notifies this AsyncListener that an asynchronous operation has failed to complete.
?void
onStartAsync(AsyncEvent?event)
??????????Notifies this AsyncListener that a new asynchronous cycle is being initiated via a call to one of the ServletRequest#startAsync methods.
?void
onTimeout(AsyncEvent?event)
Notifies this AsyncListener that an asynchronous operation has timed out.
?
可以给AsyncContext实例增加一个AsyncListener监听器，当AsyncContext调用complete()完成后即可触发onComplete(e)方法
asyncSupported要定义为true
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@WebServlet(name = "syncServlet", value = { "/syncServlet"},asyncSupported=true)
public class SyncTestServlet extends HttpServlet {
?????? private static final long serialVersionUID = -126107068129496624L;
?????? public void doGet(HttpServletRequest request, HttpServletResponse response)
???????????????????? throws ServletException, IOException {
?
????????????? response.setContentType("text/html");
????????????? PrintWriter out = response.getWriter();
????????????? out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
????????????? out.println("<HTML>");
????????????? out.println("? <HEAD><TITLE>A Servlet</TITLE></HEAD>");
????????????? out.println("? <BODY>");
????????????? out.print("??? Servlet Start:::<br>This is ");
????????????? out.print(this.getClass());
????????????? out.println("<br>using the GET method<br>");
????????????? out.flush();
????????????? //-------------增加一个异步线程
????????????? System.out.println("主response对象:"+response);
????????????? AsyncContext sc = request.startAsync(request,response);
????????????? Thread t = new Thread(new MyThread(sc));
????????????? t.start();
?????????????
?????????????
????????????? //-------------继续主线程
//注：主线程不需要等待子线程完毕，可以先执行并打印出来【异步进行】
????????????? out.println(" -------Servlet end.");???????
????????????? out.flush();
?????????????
?????? }
}
?
class MyThread extends Thread{
?????? private AsyncContext syncContext;
??????
?????? public MyThread(AsyncContext syncContext){
????????????? this.syncContext = syncContext;
?????? }
??????
?????? public void run(){
????????????? System.out.println("MyThread start2....");
????????????? HttpServletResponse resp = (HttpServletResponse) syncContext.getResponse();
????????????? System.out.println("MyThread end2....");
????????????? try {
???????????????????? PrintWriter out = resp.getWriter();
???????????????????? out.println("<br><br>-----MyThread start----");
???????????????????? out.println("<br>-----wait running.....");
???????????????????? out.flush();//flush即可先输出，不需要等全部完成
???????????????????? System.out.println("子线程里的response对象（和主线程是同一个）:"+resp);
???????????????????? Thread.sleep(3000);
???????????????????? out.println("<br>-----MyThread end----");
???????????????????? out.println("? </BODY>");
???????????????????? out.println("</HTML>");
???????????????????? out.flush();
???????????????????? //out.close();
????????????? } catch (IOException e) {
???????????????????? // TODO Auto-generated catch block
???????????????????? e.printStackTrace();
????????????? } catch (InterruptedException e) {
???????????????????? // TODO Auto-generated catch block
???????????????????? e.printStackTrace();
????????????? }
????????????? syncContext.complete();//完成异步操作
?????? }
}
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