一、根据业务需求，需要写一个实时订单的接口，

使用spring的DeferedResult进行异步推送消息到客户端

当浏览器发送请求到服务端时，请求到服务端，服务端捕获请求。待定时器更新后，再返回数据到页面

二、具体操作步骤：

1、定义Conroller类

package dcc.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.context.request.async.DeferredResult;

import dcc.service.PushService;



@RestController
@RequestMapping("/timeorder")
public class TimeOrderController {
	@Autowired
	private PushService pushService;
	

	/**
	 * 门店地图实时订单
	 * @return
	 */
	@PostMapping("/selectTimeOrder")
	public DeferredResult<String> selectTimeOrder() {
		return pushService.getAsyncUpdate();
	}
}

2、定义service类

package dcc.service;

import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Service;
import org.springframework.web.context.request.async.DeferredResult;

@Service
public class PushService {
	
	private DeferredResult<String> deferredResult;
	
	public DeferredResult<String> getAsyncUpdate(){
		deferredResult = new DeferredResult<String>();
		return deferredResult;
	}
	
	/**
	 * 10秒更新一次
	 */
	@Scheduled(fixedDelay = 10000)
	public void refreshOrder() {
		if(deferredResult!=null){
			//这里返回时间戳，可根据实际情况，查询数据库，返回对呀的数据
			deferredResult.setResult(new Long(System.currentTimeMillis()).toString());
		}
	}
}

3、spring配置文件，添加task，让@Scheduled生效

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:task="http://www.springframework.org/schema/task"  
       xsi:schemaLocation="http://www.springframework.org/schema/beans
                        http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
                        http://www.springframework.org/schema/context
                        http://www.springframework.org/schema/context/spring-context-3.1.xsd
                        http://www.springframework.org/schema/task  
						http://www.springframework.org/schema/task/spring-task-3.0.xsd 
                        http://www.springframework.org/schema/mvc
                        http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd
                         ">
   
     <!-- 定时器开关 -->
    <task:annotation-driven />   

spring配置文件中，多余的配置，没有添加，结合实际项目添加

4、配置web.xml,开启异步

 <async-supported>true</async-supported>

涉及到这个controller的每一个serlvet都要添加上，截图如下

5、编写ajax代码

 //获取服务端推送信息demo
        function getTimeOrder(){
        	$.ajax({
        		url:"http://localhost:8080/dcc/timeorder/selectTimeOrder",
        		method:"post",
        		success:function(data){
        			console.log(data);
        			getTimeOrder();
        		}
        		
        	});
        }
        getTimeOrder();

6、启动项目，效果图：