Rest api response data not saved in the database using Spring JPA

I'm new with anything Spring related, so would you please help me with this? I'm trying to write a registration api that saves some data in the database using Spring JPA.

Here is my code:

@Entity model:

@Entity
@Table(name = "registerapplications")
public class RegisterApplication {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id; 

    private String applicationId;

    public RegisterApplication (String applicationId) {
        this.applicationId = applicationId;
    }

    // Getters and Setter
}

Repository:

public interface RegisterRepository extends CrudRepository<RegisterApplication, Long>{

}

Controller:

@RestController
public class RegisterApplicationController {

    @Autowired
    private RegisterRepository registerRepository;

    @RequestMapping (path="/register", method=RequestMethod.POST)
    public @ResponseBody RegisterApplication registerApplicationController() {
        RegisterApplication registerApplication = new RegisterApplication(UUID.randomUUID().toString());
        registerRepository.save(registerApplication);
        return registerApplication;
    }   
}

application.properties:

spring.jpa.hibernate.ddl-auto=create
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/register
spring.datasource.username=admin
spring.datasource.password=admin

The request works properly, but it does not save the data in my table: Database screenshot

I get no error, so I don't know where the problem is. Would you please take a look on the code and give me some hints?