java - How to give Trigger generated value into Hibernate ValueObject?

Question

In my Hibernate Application i'm using create a ValueObject class

@Entity
@Table(name="user")
public class UserVO{

    @Id
    @Column(name="S_ID")
    private String s_id;

    @Column(name="FIRSTNAME")
    private String firstName;

    @Column(name="LASTNAME")
    private String lastName;
 }

and in my Service class i'm writing like this

public void createOrUpdateUser(UserVO userVO) {
        userDAO.createOrUpdateUser(userVO);
    }

and in my DAO class i'm writing like this

private EntityManager entityManager;
public void createOrUpdateUser(UserVO userVO) throws DataAccessException {
        entityManager.persist(userVO);
    }

now i'm calling createOrUpdateUser(userVO) but it give error

Caused by: org.hibernate.id.IdentifierGenerationException: ids for this class must be manually assigned before calling save()

Actually my data base i have created one trigger for user table to generate unique id for s_id column is their any problem for trigger..please suggest me..

Answer 1

If you are using a trigger, the intended generation strategy is org.hibernate.id.SelectGenerator. However, in order to use this strategy, Hibernate must be able to locate the inserted row after insertion to see what value the trigger assigned there are 2 ways to do this.

First is to specifically configure the generator to tell it a column that define a unique key (at least logically) within the table:

@Id
@Column(name="S_ID")
@GeneratedValue( strategy = "trigger" )
@GenericGenerator( 
    name="trigger", strategy="org.hibernate.id.SelectGenerator",
    parameters = {
        @Parameter( name="keys", value="userName" )
    }
)
private String s_id;

private String userName;

The other is via Hibernate's natural-id support:

@Id
@Column(name="S_ID")
@GeneratedValue( strategy = "trigger" )
@GenericGenerator( name="trigger", strategy="org.hibernate.id.SelectGenerator" ) )
private String s_id;

@NaturalId
private String userName;

GenerationType.IDENTITY may work for you. It will really come down to the JDBC driver and how (if) it implements getGeneratedKeys