SpringMVC之-Callable和DeferredResult异步请求

爱被打了一巴掌 2022-04-16 01:38 284阅读 0赞

*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;
    	}
    
    }

**运行tomcat结果：**

查看订单号：

![20181115110906737.png][]

![20181115110938737.png][]

结果说明：说明两个方法返回的订单号相同，说明如果有另一个线程给DeferredResult赋值后，DeferredResult在感知到自己的对象被赋值后就返回页面成功；

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或可一试哦！

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70]: /images/20220416/f352039054104af38031103b89108794.png
[20181115110906737.png]: /images/20220416/b793161b947042b68fb77351902dc35b.png
[20181115110938737.png]: /images/20220416/56acfaa698bf4736836dff617bf8b72a.png
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppbmhhaWppbmc_size_16_color_FFFFFF_t_70 1]: /images/20220416/f7b23638e5004e4897321d1e48b45f5b.png
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