Spring中注解方式的異步請(qǐng)求如何實(shí)現(xiàn)

小編給大家分享一下Spring中注解方式的異步請(qǐng)求如何實(shí)現(xiàn)，希望大家閱讀完這篇文章之后都有所收獲，下面讓我們一起去探討吧！

一、Servlet3.0異步請(qǐng)求

@WebServlet(value = "/async", asyncSupported = true)
public class HelloAsyncServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1、設(shè)置支持異步處理asyncSupported = true
        //2、開啟異步模式
        System.out.println("主線程開始:" + Thread.currentThread() + "==>" + System.currentTimeMillis());
        AsyncContext startAsync = req.startAsync();
        //3、業(yè)務(wù)邏輯進(jìn)行異步處理，開始異步處理
        startAsync.start(new Runnable() {
            @Override
            public void run() {
                try {
                    System.out.println("副線程開始:" + Thread.currentThread() + "==>" + System.currentTimeMillis());
                    sayHello();
                    //獲取到異步的上下文
                    AsyncContext asyncContext = req.getAsyncContext();
                    startAsync.complete();
                    ServletResponse response = asyncContext.getResponse();
                    response.getWriter().write("hello async!");
                    System.out.println("副線程結(jié)束:" + Thread.currentThread() + "==>" + System.currentTimeMillis());
                } catch (Exception e) {
                    e.printStackTrace();
                }

            }
        });
        System.out.println("主線程結(jié)束:" + Thread.currentThread() + "==>" + System.currentTimeMillis());
    }

    public void sayHello() throws Exception {
        System.out.println(Thread.currentThread() + "processing...");
        Thread.sleep(3000);
    }
}

打印結(jié)果：

二、SpringMVC的異步請(qǐng)求

返回Callable

@Controller
public class AsyncController {

    @ResponseBody
    @RequestMapping("/async01")
    public Callable<String> async01(){
        System.out.println("主線程開始:" + Thread.currentThread() + "==>" + System.currentTimeMillis());

        Callable<String> callable = new Callable<String>() {

            public String call() throws Exception {
                System.out.println("副線程開始:" + Thread.currentThread() + "==>" + System.currentTimeMillis());
                Thread.sleep(2000);
                System.out.println("副線程開始:" + Thread.currentThread() + "==>" + System.currentTimeMillis());

                return "async01";
            }
        };

        System.out.println("主線程結(jié)束:" + Thread.currentThread() + "==>" + System.currentTimeMillis());
        return callable;

    }
}

• 控制器返回Callable

• Spring進(jìn)行異步處理，將Callable提交給TaskExecutor，使用一個(gè)隔離的線程進(jìn)行執(zhí)行

• DispatcherServlet和所有的Filter退出Web容器的線程，但是response保持打開狀態(tài)

• Callable返回結(jié)果，SpreingMVC將請(qǐng)求重新派發(fā)給容器，恢復(fù)之前的處理，Callable返回值就是目標(biāo)方法的返回值

• 根據(jù)Callable返回的結(jié)果，SpringMVC繼續(xù)進(jìn)行視圖渲染流程等(從收到請(qǐng)求到視圖渲染)

輸出結(jié)果：

返回DeferredResult

模擬一個(gè)消息中間件

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請(qǐng)求會(huì)暫時(shí)保存DeferredResultQueue中，/create請(qǐng)求會(huì)獲取DeferredResultQueue中的請(qǐng)求，進(jìn)行業(yè)務(wù)邏輯的處理并返回結(jié)果

@Controller
public 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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