学习了spring framework的注解配置
IDEA有时候无法正确地识别 @Autowired ，并发出不应该的报错，解决办法：https://blog.csdn.net/rambler_designer/article/details/89040125?utm_medium=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-2.nonecase&depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-2.nonecase