springboot定时器：每月一号删除数据库数据，使其只保留一个月数据

1. Application：在程序的入口类中添加@EnableScheduling注解
   @SpringBootApplication
   @EnableScheduling //来快速开启任务调度功能
   public class Application extends SpringBootServletInitializer {
   @Override
   protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
   return builder.sources(Application.class);
   }
   public static void main(String[] args) {
   SpringApplication.run(Application.class, args);
   }
   }

2. Start:创建定时任务，调用dao层，实现数据库链接
   @Component //（把普通pojo实例化到spring容器中，相当于配置文件中的）
   public class Start {
   @Autowired
   private DateDeletionDao dateDeletionDao;
   public DateDeletionDao getDateDeletionDao() {
   return dateDeletionDao;
   }
   public void setDateDeletionDao(DateDeletionDao dateDeletionDao) {
   this.dateDeletionDao = dateDeletionDao;