[FIXED] JPA: How to improve performance in persistance of OneToMany relationships

Issue

I have two classes :

@Entity
@Table(name="folder")
public class Folder{
@Id
public String reference;
@OneToMany(cascade = {CascadeType.ALL}, orphanRemoval = true)
public List<Client> clients= new ArrayList<>();
public Date createDate;
}

and the second class:

@Entity
@Table(name = "client")
public class Client implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public int id;
    public String name;
}

in my database i created an intermadiate table

 create table folder_clients (folder_ref varchar(20) not null, clients_id int not null)
    alter table folder_clients add constraint UK_clientid unique (clients_id)
    alter table folder_clients add constraint FK_idClient foreign key (clients_id) references client
    alter table folder_clients add constraint FK_refFolder foreign key (folder_ref) references folder

now i have a service that persists a folder, so automatically it persists all clients related to it, and this is done throught a Folder Repository:

 folder.getClients().add(client);
 folderRepository.save(folder);

Everything is good and working, but when i execute the SQL Profiler i find that it executes many statements, which affect performance.

Is there a better way to improve my code, in order to reduce number of statements executed by hibernate and improve performance ?

thank you

Solution

Is there many-to-many association or one-to-many association between client and folder in that case?

If that is one-to-many association, I suggest you use bidirectional mapping. Because you don't need the third table for this situation. So (briefly), fewer queries will be generated by hibernate and the performance will increase.

@Entity
@Table(name="folder")
public class Folder {
    @Id
    private String reference;

    @OneToMany(mappedBy="folder", cascade = {CascadeType.ALL}, orphanRemoval = true)
    private List<Client> clients= new ArrayList<>();

    private Date createDate;

    //getters and setters
}


@Entity
@Table(name = "client")
public class Client implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;

    private String name;

    @ManyToOne
    @JoinColumn(name = "folder_id")
    private Folder folder;

    //getters and setters
}

See this awesome post about @OneToMany relationships: https://vladmihalcea.com/the-best-way-to-map-a-onetomany-association-with-jpa-and-hibernate/

But, if your case is many-to-many see: https://vladmihalcea.com/the-best-way-to-use-the-manytomany-annotation-with-jpa-and-hibernate/

Answered By - Ady Junior
Answer Checked By - Katrina (JavaFixing Volunteer)