Spring中注解方式的異步請求

更新時間：2021年06月03日 17:27:45 作者：煎丶包

今天給大家整理了Spring中注解方式的異步請求的知識點,對正在學習java的小伙伴們很有幫助,需要的朋友可以參考下

一、Servlet3.0異步請求

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

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1、設置支持異步處理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)務邏輯進行異步處理，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("副線程結束:" + Thread.currentThread() + "==>" + System.currentTimeMillis());
                } catch (Exception e) {
                    e.printStackTrace();
                }

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

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

打印結果：

在這里插入圖片描述

二、SpringMVC的異步請求

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("主線程結束:" + Thread.currentThread() + "==>" + System.currentTimeMillis());
        return callable;

    }
}

控制器返回Callable
Spring進行異步處理，將Callable提交給TaskExecutor，使用一個隔離的線程進行執(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返回結果，SpreingMVC將請求重新派發(fā)給容器，恢復之前的處理，Callable返回值就是目標方法的返回值
根據(jù)Callable返回的結果，SpringMVC繼續(xù)進行視圖渲染流程等(從收到請求到視圖渲染)

輸出結果：

在這里插入圖片描述

返回DeferredResult

模擬一個消息中間件

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請求會暫時保存DeferredResultQueue中，/create請求會獲取DeferredResultQueue中的請求，進行業(yè)務邏輯的處理并返回結果

@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;
    }
}

到此這篇關于Spring中注解方式的異步請求的文章就介紹到這了,更多相關注解方式的異步請求內容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關文章希望大家以后多多支持腳本之家！

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