SpringMVC之-Callable和DeferredResult异步请求

Callable和DeferredResult均是SpringMVC中处理异步请求的方法；

Callable异步请求步骤：

* 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

一、返回Callable

新建AsyncController .java

package com.atguigu.controller;
import java.util.UUID;
import java.util.concurrent.Callable;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.context.request.async.DeferredResult;
import com.atguigu.service.DeferredResultQueue;
@Controller
public 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>() {
            @Override
            public String call() throws Exception {
                System.out.println("副线程开始..."+Thread.currentThread()+"==>"+System.currentTimeMillis());
                Thread.sleep(2000);
                System.out.println("副线程结束..."+Thread.currentThread()+"==>"+System.currentTimeMillis());
                return "Callable<String> async01()";
            }
        };
        System.out.println("主线程结束..."+Thread.currentThread()+"==>"+System.currentTimeMillis());
        return callable;
    }
}

运行tomcat结果:

watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70

二、返回 DeferredResult

1、新建一个队列

package com.atguigu.service;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
import org.springframework.web.context.request.async.DeferredResult;
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();
    }
}

2、新建AsyncController.java

package com.atguigu.controller;
import java.util.UUID;
import java.util.concurrent.Callable;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.context.request.async.DeferredResult;
import com.atguigu.service.DeferredResultQueue;
@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);
        return "success===>"+order;
    }
}