Spring Data JPA / Hibernate generating single id for all the entities persisted within single transaction

I have a legacy application which I am trying to migrate to newer Apache Camel Spring Boot application where I am using Spring Data JPA and Hibernate as an ORM framework. Sybase is the DB used by application.

I have many JPA entities available where ids are annotated with:

@Id
@Column(name = "entity_pk")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long entity_pk;

I have a single method where I am trying to create multiple entities and then persisting all the entities one by one into the DB using JpaRepository save() method. All this is happening within a single transaction

My issue here is, hibernate is generating only one unique id and using it while persisting all the entities.

What I am looking for is a way to tell hibernate to check the latest value in the primary key i.e. entity_key column of each table and then generate the next value. Sort of auto incremented value for each row. Columns are created as IDENTITY column in the database.

I do not want to use any custom id generator for this. Is there any way to achieve this just by using annotations and/or configurations?

EDIT 1: <br/>
Just wanted to give background on existing legacy application. This application uses Hibernate 3.x and uses <generator class="native"> which apparently works as expected. I confirmed that from existing DB values.

I am using Hibernate 5.x along with Spring boot 2.x and Spring 5.x.

I have tried using GenerationType.AUTO along with hibernate.id.new_generator_mappings=false just to make sure the LegacyFallbackInterpreter kicks in as per the instructions given here: <br/>
https://stackoverflow.com/questions/1212535/the-equivalent-of-generator-class-native-generator-using-mysql-and-hiberna
<br/><br/>
But nothing works.

Edit 2:<br/>
Adding some sample code. It is not the exact code but similar to what I am trying to achieve in my application.<br/>
Entity classes:

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@ToString
@Entity
@Table(name = "block")
public class Block {

    @Id
    @Column(name = "block_pk")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long blockPk;

    @Version
    @Column(name = "version")
    private int version;

    @OneToMany(mappedBy = "block", cascade = CascadeType.ALL, orphanRemoval = true)
    @OrderBy("allocationPk")
    @Fetch(FetchMode.SELECT)
    @ToString.Exclude
    private Set<Allocation> allocations;

    @Column(name = "quantity")
    private BigDecimal quantity;

    public void addAllocation(Allocation allocation) {
        if (allocations == null) {
            allocations = new HashSet<>();
        }

        allocations.add(allocation);
    }
}

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@ToString
@Entity
@Table(name = "allocation")
public class Allocation {

    @Id
    @Column(name = "allocation_pk")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long allocationPk;

    @Version
    @Column(name = "version")
    private int version;

    @ManyToOne
    @JoinColumn(name = "block_pk", nullable = false)
    @Fetch(FetchMode.SELECT)
    @ToString.Exclude
    private Block block;

    @Column(name = "quantity")
    private BigDecimal quantity;
}

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@ToString
@Entity
@Table(name = "booking")
public class Booking {
    @Id
    @Column(name = "booking_pk")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long bookingPk;

    @Version
    @Column(name = "version")
    private int version;

    @Column(name = "block_Id")
    private Long blockId;
}

<br/><br/>
Repositories:

@Repository
public interface BlockRepository extends JpaRepository<Block, Long> {
}

@Repository
public interface AllocationRepository extends JpaRepository<Allocation, Long> {
}

@Repository
public interface BookingRepository extends JpaRepository<Booking, Long> {
}

@Component
public class DbStore {
    @Autowired
    private BlockRepository blockRepository;
    @Autowired
    private AllocationRepository allocationRepository;
    @Autowired
    private BookingRepository bookingRepository;

    public Block save(Block block) {
        return blockRepository.save(block);
    }

    public Allocation save(Allocation allocation) {
        return allocationRepository.save(allocation);
    }

    public Booking save(Booking booking) {
        return bookingRepository.save(booking);
    }
}

<br/><br/>
Service Class:

@Service
public class AllocationHandler {
    private static final Logger LOGGER = LoggerFactory.getLogger(AllocationHandler.class);
    @Autowired
    private DbStore dbStore;

    public List<Allocation> handleRequest(String input) {
        Block block = new Block();
        block.setQuantity(new BigDecimal(1000000));

        // Persist Block
        LOGGER.info("Persist block in DB");
        block = dbStore.save(block);
        LOGGER.info("Persisted Block in DB with Id [{}]", block.getBlockPk());

        Allocation allocation = new Allocation();
        allocation.setQuantity(new BigDecimal(500000));

        block.addAllocation(allocation);
        allocation.setBlock(block);

        LOGGER.info("Persist allocation in DB");
        allocation = dbStore.save(allocation);
        LOGGER.info("Persisted allocation in DB with Id [{}]", allocation.getAllocationPk());

        LOGGER.info("Update Block");
        block = dbStore.save(block);

        Booking booking = new Booking();
        booking.setBlockId(block.getBlockPk());

        LOGGER.info("Persist booking in DB");
        booking = dbStore.save(booking);
        LOGGER.info("Persisted Booking in DB with Id [{}]", booking.getBookingPk());

        return Arrays.asList(allocation);
    }
}

<br/><br/>
Driver Class:

@Component
public class Transformer {
    @Autowired
    private AllocationHandler allocationHandler;

    public void transform(String input) {
        allocationHandler.handleRequest(input);
    }
}

<br/><br/>
Main:

@SpringBootApplication
@EnableJpaRepositories(basePackages = "com.example.demo.repository")
public class DemoApplication implements ApplicationRunner {
	@Autowired
	private Transformer transformer;

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

	@Override
	public void run(ApplicationArguments args) throws Exception {
		transformer.transform("Test");
	}
}

<br/><br/>
I have also added this code in Github:<br/> https://github.com/viveksinghr89/spring-data-jpa-poc
<br/><br/>
I am unable to replicate it completely but yes partially it is working like the actual project wherein Block and Allocation are using the same id instead of using different ids as per the latest value in their identity column.
<br/><br/>
Logs:

2023-04-17T23:41:05.674+05:30  INFO 21052 --- [           main] com.example.demo.DemoApplication         : Started DemoApplication in 6.195 seconds (process running for 6.718)
2023-04-17T23:41:05.678+05:30  INFO 21052 --- [           main] com.example.demo.AllocationHandler       : Persist block in DB
2023-04-17T23:41:05.755+05:30  INFO 21052 --- [           main] com.example.demo.AllocationHandler       : Persisted Block in DB with Id [97]
2023-04-17T23:41:05.755+05:30  INFO 21052 --- [           main] com.example.demo.AllocationHandler       : Persist allocation in DB
2023-04-17T23:41:05.761+05:30  INFO 21052 --- [           main] com.example.demo.AllocationHandler       : Persisted allocation in DB with Id [97]
2023-04-17T23:41:05.761+05:30  INFO 21052 --- [           main] com.example.demo.AllocationHandler       : Update Block
2023-04-17T23:41:05.823+05:30  INFO 21052 --- [           main] com.example.demo.AllocationHandler       : Persist booking in DB
2023-04-17T23:41:05.825+05:30  INFO 21052 --- [           main] com.example.demo.AllocationHandler       : Persisted Booking in DB with Id [65]

<br/><br/>
H2 DB Screenshot:

<br/><br/>
Please let me know if you are able to figure something out. Would be really helpful. Thank you.

I have tested similar configuration with H2 file database. Apparently there is no guarantee that the id will be generated without gaps. The only guarantee is that they will be unique.

In my case after the first run of the application with an empty database the ids started with 1 and were incremented by 1. But after restart (without dropping the tables) the id continued with 33, 34 etc.