Spring中注解方式的异步请求如何实现

小编给大家分享一下spring中注解方式的异步请求如何实现，希望大家阅读完这篇文章之后都有所收获，下面让我们一起去探讨吧！

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, IOException {        //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

@Controllerpublic class AsyncController {    @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>() {            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<DeferredResult<Object>> queue = new ConcurrentLinkedDeque<DeferredResult<Object>>();        public static void save(DeferredResult<Object> deferredResult){        queue.add(deferredResult);    }        public static DeferredResult<Object> get(){        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

@Controllerpublic class AsyncController {    @ResponseBody    @RequestMapping("/createOrder")    public DeferredResult<Object> createOrder(){        DeferredResult<Object> deferredResult = new DeferredResult<Object>((long)3000,"create fail");        DeferredResultQueue.save(deferredResult);        return deferredResult;    }    @ResponseBody    @RequestMapping("/create")    public String create(){        String order = UUID.randomUUID().toString();        DeferredResult<Object> deferredResult = DeferredResultQueue.get();        deferredResult.setResult(order);        return "success:" + order;    }}

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