In actual work, we will encounter some time-consuming operations. At this time, if the response is not timely, it will return failure. If you want to perform asynchronous operations and return data with a delay, you can use the following methods
Use asyncSupported = trueannotations
@WebServlet(name = "apitest", asyncSupported = true)
If you don’t use this annotation, an error will be reported during access
The following is the source code
@WebServlet(name = "apitest", asyncSupported = true)
public class apitest extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request,response);
}
private volatile ExecutorService executorService;
@Override
public void init() throws ServletException {
super.init();
//newFixedThreadPool 创建一个定长线程池，可控制线程最大并发数，超出的线程会在队列中等待。
executorService = Executors.newFixedThreadPool(100);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
AsyncContext asyncCtx = request.startAsync();
executorService.submit(new Runnable() {
@Override
public void run() {
//延时5秒 ，模拟耗时操作
try {
Thread.sleep (5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
PrintWriter writer = null;
try {
writer = asyncCtx.getResponse().getWriter();
} catch (IOException e) {
e.printStackTrace();
}
//返回数据
writer.println("servlevt异步处理成功");
writer.flush();//记得关闭
asyncCtx.complete();//记得关闭
}
}, asyncCtx);
}
}
Restart tomcat, access the interface /apitest, you can see that after waiting for 5 seconds, the servlevt asynchronous processing success is returned. thread.sleep(), this is generally not needed, and time-consuming operations can be written in actual applications.