[FIXED] Hibernate 6 perfroms update query after select query

Issue

I wrote a simple entity named "User" and another one called "Company". User entity has company inside with @ManyToOne(fetch = LAZY) mapping. When I create the session object and call get() method Hibernate executes select query and after it update, why?

User entity:

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@EqualsAndHashCode
@ToString
@Builder
@Entity
@Table(name = "users")
public class User2 {
    @Id
    @GeneratedValue(strategy = IDENTITY)
    private Long id;

    @Column(unique = true)
    private String username;

    @Embedded
    @EqualsAndHashCode.Exclude
    private PersonalInfo personalInfo;

    @Enumerated(STRING)
    @EqualsAndHashCode.Exclude
    private Role role;

    @Type(JsonType.class)
    @EqualsAndHashCode.Exclude
    private String info;

    @ManyToOne(fetch = LAZY)
    @JoinColumn(name = "company_id")
    @EqualsAndHashCode.Exclude
    @ToString.Exclude
    private Company company;
}

Company entity:

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@EqualsAndHashCode
@ToString
@Builder
@Entity
public class Company {
    @Id
    @GeneratedValue(strategy = IDENTITY)
    private Long id;

    private String name;
}

Main:

public class HibernateEntityMappingRunner {
    public static void main(String[] args) {
        try (SessionFactory sessionFactory = buildSessionFactory();
             Session session = sessionFactory.openSession()
        ) {
            session.beginTransaction();

            User2 user2 = session.get(User2.class, 2);

            session.getTransaction().commit();
        }
    }
}

Hibernate console log:

Hibernate: 
    select
        u1_0.id,
        u1_0.company_id,
        u1_0.info,
        u1_0.birth_date,
        u1_0.firstname,
        u1_0.lastname,
        u1_0.role,
        u1_0.username 
    from
        users u1_0 
    where
        u1_0.id=?
Hibernate: 
    update
        users 
    set
        company_id=?,
        info=?,
        birth_date=?,
        firstname=?,
        lastname=?,
        role=?,
        username=? 
    where
        id=?

Solution

See https://hibernate.org/community/contribute/intellij-idea/#debugging for details. The problem is that some of your toString() implementations (which the IntelliJ debugger invokes) access state of uninitialized entity/collection proxies, which will cause lazy initialization and hence a select query. If you have pending flushes (insert/update/delete) which affect one of the tables that are about to be selected from, Hibernate forcefully executes pending flushes.

By changing your toString() implementations or changing how IntelliJ shows objects in the debugger, you can avoid this.

Answered By - Christian Beikov
Answer Checked By - Terry (JavaFixing Volunteer)