I think it does not make sense to execute query and load full entity if I just need to fetch id of proxy object and this proxy has FK id.
I have Client and Account entities.
Account table has a FK on Client. (id_client)
relationship - one-to-many:
{code}
@Entity
class Client {
@OneToMany(mappedBy="client")
private List<Account> accounts;
}
@Entity
class Account {
@JoinColumn(name = "id_client")
@ManyToOne(fetch = FetchType.LAZY)
private Client client;
}
{code}
{code}
Account account = em.find(Account.class, 2);
account.getClient().getId();
{code}
console output:
{code}
Hibernate:
select
account0_.id_account as id_accou1_0_0_,
account0_.AMOUNT as AMOUNT2_0_0_,
account0_.id_client as id_clien3_0_0_
from
ACCOUNT account0_
where
account0_.id_account=2
Hibernate:
select
client0_.ID_CLIENT as ID_CLIEN1_4_0_,
client0_.age as age2_4_0_,
client0_.create_date as create_d3_4_0_,
client0_.modify_date as modify_d4_4_0_,
client0_.NAME as NAME5_4_0_,
client0_.vip as vip6_4_0_
from
client client0_
where
client0_.ID_CLIENT=1
{code}
There is id_client column in Account table
{code}
id_account | amount | id_client
{code}
Account object has javassist proxy client object, that proxy client has JavassistLazyInitializer handler field and there is id field. Take a look at attached file.
Why don't just retrieve that id from handler object??? It would be great performance optimization I suppose, cause very often just id is needed
P.S.: the same stuff is for load method:
{code}
Client client = em.unwrap(Session.class).load(Client.class, 1); // - proxy
client.getId(); // select is executed
{code}
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