Servlet中的异步
@WebServlet(value="/async",asyncSupported=true)
public class HelloAsyncServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//1、支持异步处理asyncSupported=true
//2、开启异步模式
System.out.println("主线程开始。。。"+Thread.currentThread()+"==>"+System.currentTimeMillis());
AsyncContext startAsync = req.startAsync();
//3、业务逻辑进行异步处理;开始异步处理
startAsync.start(new Runnable() {
@Override
public void run() {
try {
System.out.println("副线程开始。。。"+Thread.currentThread()+"==>"+System.currentTimeMillis());
sayHello();
startAsync.complete();
//获取到异步上下文
AsyncContext asyncContext = req.getAsyncContext();
//4、获取响应
ServletResponse response = asyncContext.getResponse();
response.getWriter().write("hello async...");
System.out.println("副线程结束。。。"+Thread.currentThread()+"==>"+System.currentTimeMillis());
} catch (Exception e) {
}
}
});
System.out.println("主线程结束。。。"+Thread.currentThread()+"==>"+System.currentTimeMillis());
}
public void sayHello() throws Exception{
System.out.println(Thread.currentThread()+" processing...");
Thread.sleep(3000);
}
}
SpringMvc中的异步——Callable
@Controller
public class AsyncController {
/**
* 1、控制器返回Callable
* 2、Spring异步处理,将Callable 提交到 TaskExecutor 使用一个隔离的线程进行执行
* 3、DispatcherServlet和所有的Filter退出web容器的线程,但是response 保持打开状态;
* 4、Callable返回结果,SpringMVC将请求重新派发给容器,恢复之前的处理;
* 5、根据Callable返回的结果。SpringMVC继续进行视图渲染流程等(从收请求-视图渲染)。
*
* preHandle.../springmvc-annotation/async01
主线程开始...Thread[http-bio-8081-exec-3,5,main]==>1513932494700
主线程结束...Thread[http-bio-8081-exec-3,5,main]==>1513932494700
=========DispatcherServlet及所有的Filter退出线程============================
================等待Callable执行==========
副线程开始...Thread[MvcAsync1,5,main]==>1513932494707
副线程开始...Thread[MvcAsync1,5,main]==>1513932496708
================Callable执行完成==========
================再次收到之前重发过来的请求========
preHandle.../springmvc-annotation/async01
postHandle...(Callable的之前的返回值就是目标方法的返回值)
afterCompletion...
异步的拦截器:
1)、原生API的AsyncListener
2)、SpringMVC:实现AsyncHandlerInterceptor;
* @return
*/
@ResponseBody
@RequestMapping("/async01")
public Callable<String> async01(){
System.out.println("主线程开始..."+Thread.currentThread()+"==>"+System.currentTimeMillis());
Callable<String> callable = new Callable<String>() {
@Override
public String call() throws Exception {
System.out.println("副线程开始..."+Thread.currentThread()+"==>"+System.currentTimeMillis());
Thread.sleep(2000);
System.out.println("副线程开始..."+Thread.currentThread()+"==>"+System.currentTimeMillis());
return "Callable<String> async01()";
}
};
System.out.println("主线程结束..."+Thread.currentThread()+"==>"+System.currentTimeMillis());
return callable;
}
}
SpringMvc中的异步——DeferredResult
@Controller
public class AsyncController {
@ResponseBody
@RequestMapping("/createOrder")
public DeferredResult<Object> createOrder(){
DeferredResult<Object> deferredResult = new DeferredResult<>((long)3000, "create fail...");
DeferredResultQueue.save(deferredResult);
return deferredResult;
}
@ResponseBody
@RequestMapping("/create")
public String create(){
//创建订单
String order = UUID.randomUUID().toString();
DeferredResult<Object> deferredResult = DeferredResultQueue.get();
deferredResult.setResult(order);//上一步的响应结果
return "success===>"+order;
}
}
模拟中间件
public class DeferredResultQueue {
private static Queue<DeferredResult<Object>> queue = new ConcurrentLinkedQueue<DeferredResult<Object>>();
public static void save(DeferredResult<Object> deferredResult){
queue.add(deferredResult);
}
public static DeferredResult<Object> get( ){
return queue.poll();
}
}