@Configuration
@EnableTransactionManagement
public class JpaConfiguration extends JpaBaseConfiguration {

    protected JpaConfiguration(DataSource dataSource, JpaProperties properties, ObjectProvider<JtaTransactionManager> jtaTransactionManager, ObjectProvider<TransactionManagerCustomizers> transactionManagerCustomizers) {
        super(dataSource, properties, jtaTransactionManager, transactionManagerCustomizers);
    }

    @Override
    protected AbstractJpaVendorAdapter createJpaVendorAdapter() {
        return new EclipseLinkJpaVendorAdapter();
    }

    @Override
    protected Map<String, Object> getVendorProperties() {
        return new HashMap<>(0);
    }

    @Bean("transactionManager")
    public PlatformTransactionManager createTransactionManager(EntityManagerFactory entityManagerFactory) {
        TenantAwareJpaTransactionManager txManager = new TenantAwareJpaTransactionManager();
        txManager.setEntityManagerFactory(entityManagerFactory);

        return txManager;
    }
}

@Slf4j
public class TenantAwareJpaTransactionManager extends JpaTransactionManager {

    @Override
    protected void doBegin(Object transaction, TransactionDefinition definition) {
        super.doBegin(transaction, definition);

        final EntityManagerHolder emHolder = (EntityManagerHolder) TransactionSynchronizationManager.getResource(getEntityManagerFactory());
        final EntityManager em = emHolder.getEntityManager();

        String tenant = TenantContext.getCurrentTenant();
        if (StringUtils.isEmpty(tenant)) {
            throw new NoTenantProvidedException();
        }
        log.info("{} is set to EntityManager", tenant);
        em.setProperty(EntityManagerProperties.MULTITENANT_PROPERTY_DEFAULT, tenant);
    }

    class NoTenantProvidedException extends RuntimeException {

        public NoTenantProvidedException() {
            super("No tenant identifier could be resolved instance.");
        }
    }
}

@Slf4j
@Service
public class CustomerService {
    @PersistenceContext
    EntityManager entityManager;

    private final CustomerRepository customerRepository;

    public CustomerService(CustomerRepository customerRepository) {
        this.customerRepository = customerRepository;
    }

    @Transactional
    public Customer add(Customer customer) {
        setTenant();
        return this.customerRepository.save(customer);
    }

    @Transactional
    public Customer update(Long customerId, Customer customer) {
        setTenant();

        Optional<Customer> temp = this.customerRepository.findById(customerId);
        if (temp.isPresent()) {
            temp.get().setFirstName(customer.getFirstName());
            temp.get().setLastName(customer.getLastName());
            return temp.get();
        }
        return null;
    }

    @Transactional(readOnly = true, propagation = Propagation.REQUIRES_NEW)
    public List<Customer> getAll() {
        setTenant();

        return this.customerRepository.findAll();
    }

    @Transactional
    public void delete(Long customerId) {
        setTenant();

        Optional<Customer> temp = this.customerRepository.findById(customerId);
        if (temp.isPresent()) {
            this.customerRepository.delete(temp.get());
        }
    }

    private void setTenant(){
        log.info("Current tenant : {}", TenantContext.getCurrentTenant());
        this.entityManager.setProperty(EntityManagerProperties.MULTITENANT_PROPERTY_DEFAULT, TenantContext.getCurrentTenant());
    }
}

 curl -X GET http://localhost:8080/customers -H 'Accept: application/json' -H 'X-TenantID: TENANT2'