JPA repository retrieve custom primary key value after save - jpa

Question

I have an entity class pointing to postgresql table. Below is table structure. The paymentreferencenumber is the PK which is populated by a trigger. id field is the sequence generated field. When i try to save in this table using JPARepository save method it inserts the first record. But after that it fails due to the primary key constraint. Since PK is a string type and generated using trigger I am specifying generator strategy as 'select'. Can anyone help me with this blocker and point me in the right direction. Thanks
Table structure --
custId serial not null,
paymentreferencenumber varchar(32) not null
constraint customers1_pkey
primary key,
firstname varchar(255),
lastname varchar(255)
Entity class --
#Entity
#Table(name = "customersnew")
public class Customer implements Serializable {
private static final long serialVersionUID = -1L;
#GeneratedValue(generator = "seq")
#GenericGenerator(name="seq", strategy="sequence", parameters = { #Parameter(name="key", value = "customersnew_custid_seq")})
#Column(name = "custid")
private long id;
#Id
#GeneratedValue(generator = "trigger_generated")
#GenericGenerator(name="trigger_generated", strategy="select", parameters = { #Parameter(name="key", value = "id")})
#Column(name = "paymentreferencenumber")
private String refNum;
#Column(name = "firstname")
private String firstName;
#Column(name = "lastname")
private String lastName;
}
--- Controller using JPA save
#RestController
public class CustomerController {
#Autowired
CustomerRepository repository;
EntityManagerFactory emf;
public CustomerController(CustomerRepository repository, EntityManagerFactory emf) {
this.repository = repository;
this.emf = emf;
}
#PostMapping("/create")
public String create(#RequestBody CustomerUI customer){
// save a single Customer
Customer returnObj = repository.saveAndFlush(new Customer(customer.getFirstName(), customer.getLastName()));
PersistenceUnitUtil util = emf.getPersistenceUnitUtil();
Object retObj = util.getIdentifier(returnObj);
return "Customer is created";
}

Answer 1

If you don't specify an id generation strategy, Hibernate will use GenerationType.AUTO. This will result in any of
AUTO - either identity column, sequence or table depending on the
underlying DB.
If you look here, you'll notice all of those generate ids of type long, short or int, not of type String.
Say you wanted a String UUID as an id, you could use
#Id
#GeneratedValue(generator = "uuid")
#GenericGenerator(name = "uuid", strategy = "uuid2")
#Column(name = "paymentreferencenumber")
private String refNum;