How to use @Cacheable with redis using spring boot

I am trying to implement hashmap using redis but I would like to control the key myself, so I have implemented following service class.

@Slf4j@Servicepublic class RedisService {    Map<Long, Student> studentMap = new HashMap<>();    @Cacheable(cacheNames = "studentCache")    public Map<Long, Student> getStudentCache(){        return studentMap;    }}

my pojo class is

@Datapublic class Student implements Serializable {    private static final long serialVersionUID = -2722504679276149008L;    public enum Gender {        MALE, FEMALE    }    private Long id;    private String name;    private Gender gender;    private int grade;}

and the data loader

@Slf4j@Componentpublic class DataLoader implements CommandLineRunner {    @Autowired    RedisService redisService;    @Override    public void run(String... args) {      log.info("================ loading data now ========================");        Student student = getStudent();        redisService.getStudentCache().put(student.getId(), student);        System.out.println("student is "+redisService.getStudentCache().get(student.getId()));        log.info("================= program ends ==============");    }    private Student getStudent() {        Student student = new Student();        student.setId(ThreadLocalRandom.current().nextLong());        student.setName("first last");        student.setGender(Student.Gender.MALE);        student.setGrade(85);        return student;    }}

Main class

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

I have successfull connection with redis but it does not seems to be putting anything in the cache. When I run the program I got following message as outcome.

2020-09-10 15:26:37.605  INFO 28540 --- [           main] c.w.s.components.DataLoader              : ================ loading data now ========================student is null2020-09-10 15:26:38.295  INFO 28540 --- [           main] c.w.s.components.DataLoader              : ================= program ends ==============

So I am not sure why student is returning NULL any help would be appreciated.