Spring中注解方式的异步请求

Spring中注解方式的异步请求

一、Servlet3.0异步请求

@WebServlet(value = "/async", asyncSupported = true)

public class HelloAsyncServlet extends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOExceptiohttp://n {

//1、设置支持异步处理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();

//获取到异步的上下文

AsyncContext asyncContext = req.getAsyncContext();

startAsync.complete();

ServletResponse response = asyncContext.getResponse();

response.getWriter().write("hello async!");

System.out.println("副线程结束:" + Thread.currentThread() + "==>" + System.currentTimeMillis());

} catch (Exception e) {

e.printStackTrace();

}

}

});

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);

}

}

打印结果：

二、SpringMVC的异步请求

返回Callable

@Controller

public class AsyncController {

@ResponseBody

@RequestMapping("/async01")

public Callable async01(){

System.out.println("主线程开始:" + Thread.currentThread() + "==>" + System.currentTimeMillis());

Callable callable = new Callable() {

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 "async01";

}

};

System.out.println("主线程结束:" + Thread.currentThread() + "==>" + System.currentTimeMillis());

return callable;

}

}

控制器返回Callable

Spring进行异步处理，将Callable提交给TaskExecutor，使用一个隔离的线程进行执行

DispatcherServlet和所有的Filter退出Web容器的线程，但是response保持打开状态

Callable返回结果，SpreingMVC将请求重新派发给容器，恢复之前的处理，Callable返回值就是目标方法的返回值

根据Callable返回的结果，SpringMVC继续进行视图渲染流程等(从收到请求到视图渲染)

输出结果：

返回DeferredResult

模拟一个消息中间件

public class DeferredResultQueue {

private static Queue> queue = new ConcurrentLinkedDeque>();

public static void save(DeferredResult

queue.add(deferredResult);

}

public static DeferredResult

return queue.poll();

}

}

/createOrder请求会暂时保存DeferredResultQueue中，/create请求会获取DeferredResultQueue中的请求，进行业务逻辑的处理并返回结果

@Controller

public class AsyncController {

@ResponseBody

@RequestMapping("/createOrder")

public DeferredResult

DeferredResult

DeferredResultQueue.save(deferredResult);

return deferredResult;

}

@ResponseBody

@RequestMapping("/create")

public String create(){

String order = UUID.randomUUID().toString();

DeferredResult

deferredResult.setResult(order);

return "success:" + order;

}

}

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