在上一节JPA操作基础上修改

Cache缓存策略：使更少的操作数据库，更快的返回数据

1、引入cache依赖

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-cache</artifactId>
</dependency>

2.主要是修改UserSerViceImpl服务层实现类

@Service
@Transactional  //事务
public class UserServiceImpl implements UserService {

    @Autowired
    private UserRepository userRepository;

    @Override
    @Cacheable(value = "user", key = "#id")
    public User findUserById(Integer id) {
        System.out.println("查询用户查询数据库");
        return userRepository.getOne(id);
    }

    @Override
    @Cacheable(value = "userListPage" , key = "#pageable") //key值可视化,每页的key值是不同的
    public Page<User> findUserListPage(Pageable pageable) {
        System.out.println("分页查询数据库");
        return userRepository.findAll(pageable);
    }
    @Override
    //@CacheEvict(value = "users",key = "#id")  //清空缓存中以users和key值缓存策略缓存的对象
    @CacheEvict(value = "userListPage",allEntries = true)  //清空所有缓存中以users缓存策略缓存的对象
    public void saveUser(User user) {
        userRepository.save(user);
    }

    /*
        注解Caching可以混合几个注解
     */
    @Override
    @Caching(evict = {@CacheEvict(cacheNames = "user",key = "#user.id"),
            @CacheEvict(cacheNames = "user2" ,key = "user2.id")})
    public void updateUser(User user) {

    }

}

3.测试TsetController类

@Controller
public class TestController {

    @Autowired
    private UserService userService;
 
    @RequestMapping("/getUserById")
    public @ResponseBody User getUserById(){
        System.out.println(userService.findUserById(1527));
        System.out.println(userService.findUserById(1527));
        System.out.println(userService.findUserById(1528));
        return userService.findUserById(1527);
    }
  
}

4.对启动类添加缓存注解

@SpringBootApplication
@EnableCaching  //对缓存做配置
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

}

5.进行测试：

运行结果：

第二次查询数据库是因为id不同没有这个缓存，会去查询数据库的