我们先让代码跑起来，来一个简单的例子。

一、引入jar包

<dependency>
  <groupId>com.dangdang</groupId>
  <artifactId>elastic-job-lite-core</artifactId>
  <version>2.1.5</version>
</dependency>

<!-- 这里要注意，我们和Spring集成，要引入这个jar包 -->
<dependency>
  <groupId>com.dangdang</groupId>
  <artifactId>elastic-job-lite-spring</artifactId>
  <version>2.1.5</version>
</dependency>

二、代码开发

1.配置文件

在/Davis/src/main/resources/目录下增加spring-job目录，并新建文件spring-job.xml。

<?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:reg="http://www.dangdang.com/schema/ddframe/reg"
    xmlns:job="http://www.dangdang.com/schema/ddframe/job"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
                        http://www.springframework.org/schema/beans/spring-beans.xsd
                        http://www.dangdang.com/schema/ddframe/reg
                        http://www.dangdang.com/schema/ddframe/reg/reg.xsd
                        http://www.dangdang.com/schema/ddframe/job
                        http://www.dangdang.com/schema/ddframe/job/job.xsd
                        ">
    <!--配置作业注册中心 zookeeper_url=10.136.19.170:2181,zookeeper_namespace=elastic-job这个可以自己任意起名字 -->
    <reg:zookeeper id="regCenter" 
        server-lists="${zookeeper_url}" 
        namespace="${zookeeper_namespace}" 
        base-sleep-time-milliseconds="1000" 
        max-sleep-time-milliseconds="3000" 
        max-retries="3" />
    
    <!-- 配置作业 -->
    <job:simple id="demoSimpleSpringJob" class="com.spring.lw.job.UserElasticJob" 
        registry-center-ref="regCenter" 
        cron="0/10 * * * * ?" 
        sharding-total-count="3" 
        sharding-item-parameters="0=A,1=B,2=C" />

</beans>

2.代码

package com.spring.lw.job;

import com.dangdang.ddframe.job.api.ShardingContext;
import com.dangdang.ddframe.job.api.simple.SimpleJob;

public class UserElasticJob implements SimpleJob {

    @Override
    public void execute(ShardingContext context) {
        // TODO Auto-generated method stub
        switch (context.getShardingItem()) {
            case 0: 
                System.out.println("UserElasticJob execute context = " + 0);
                break;
            case 1: 
                System.out.println("UserElasticJob execute context = " + 1);
                break;
            case 2: 
                System.out.println("UserElasticJob execute context = " + 2);
                break;
            // case n: ...
        }
    }

}

3.运行

放到Tomcat跑一下看看，当然zookeeper要先启动起来。
控制台会输出：

UserElasticJob execute context = 0
UserElasticJob execute context = 1
UserElasticJob execute context = 2

反正是跑起来了，虽然到现在看起来没什么卵用。

我们把这个工程部署到两个Tomcat试试，启动两个Tomcat，会发现。
Tomcat1的控制台输出：

UserElasticJob execute context = 0
UserElasticJob execute context = 2

Tomcat2的控制台输出：

UserElasticJob execute context = 1

好像体会到一点好处了。