Javadb generating sequence of ids with 3 digits

Question

I’m trying to learn Hibernate with JPA, I did a test to record in the Javadb database and realized that the id autoincrement instead of generating an initial sequence of a digit (1,2,3,4...) is generating a sequence that starts at 1 and jumps to the 101, 201, 301, 401... That is, to each new record it adds 100 to the ID.

How to make the autoincrement stay normal, generating 1,2,3,4?

Why and how useful it is to generate an id with this sequence?

Client class

@Entity
public class Cliente {

    @Id
    @GeneratedValue
    private int id;
    @Column(nullable=false, length=100)
    private String nome;
    @Column(nullable=false, length=250)
    private String endereco;
    @Column(nullable=false, length=8)
    private int rg;
    @Column(nullable=false, length=12)
    private int cpf;
    @Temporal(TemporalType.DATE)
    private Date date;
    @Temporal(TemporalType.TIME)
    private Date time;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getNome() {
        return nome;
    }

    public void setNome(String nome) {
        this.nome = nome;
    }

    public String getEndereco() {
        return endereco;
    }

    public void setEndereco(String endereco) {
        this.endereco = endereco;
    }

    public int getRg() {
        return rg;
    }

    public void setRg(int rg) {
        this.rg = rg;
    }

    public int getCpf() {
        return cpf;
    }

    public void setCpf(int cpf) {
        this.cpf = cpf;
    }

    public Date getDate() {
        return date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    public Date getTime() {
        return time;
    }

    public void setTime(Date time) {
        this.time = time;
    }

}

The test in the Main class

public class Main {

    public static void main(String args[]){
        System.out.println("Worked!");
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("teste");

        Cliente cliente = new Cliente();
        cliente.setNome("Joao");
        cliente.setCpf(58756456);
        cliente.setDate(new Date());
        cliente.setTime(new Date());
        cliente.setRg(4568);
        cliente.setEndereco("Rua dos anjos n 666");
        EntityManager entityManager = factory.createEntityManager();
        entityManager.getTransaction().begin();
        entityManager.persist(cliente);
        entityManager.getTransaction().commit();
        entityManager.close();
    }
}

Table screenshot in Javadb:

Edit: (I forgot to put persistence.xml)

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
  <persistence-unit name="teste" transaction-type="RESOURCE_LOCAL">
    <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
    <properties>
      <property name="dialect" value="org.hibernate.dialect.DerbyDialect"/>
      <property name="connection.driver_class" value="org.apache.derby.jdbc.EmbeddedDriver"/>
      <property name="hibernate.show_sql" value="true"/>
      <property name="hibernate.format_sql" value="true"/>
      <property name="hibernate.hbm2ddl.auto" value="create"/>
      <!--  atualiza o banco, gera as tabelas se for preciso -->
      <property name="javax.persistence.jdbc.url" value="jdbc:derby:Teste01;create=true"/>
      <!--<property name="javax.persistence.jdbc.user" value="root"/> -->
      <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.EmbeddedDriver"/>
      <!-- <property name="javax.persistence.jdbc.password" value=""/> -->
      <property name="javax.persistence.schema-generation.database.action" value="create"/>
    </properties>
  </persistence-unit>
</persistence>

Answer 1

From JPA 2.1 (Java EE 7) the annotation Column won an attribute columnDefinition which can be used to change the definition of a field. Example:

@Id
@GeneratedValue
@Column(name="ID", columnDefinition="INTEGER NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY 1")
private int id;

But in the case of Derby (Javadb is a variation of Derby packaged by Oracle) incrementing by 1 is the default (see official documentation)

I would guess that you’re seeing increments of 100 due to preallocation of values. You’re probably not "shutting down" your database, so every time you run your application it allocates a new block.

In accordance with that answer in Soen the two options are:

1. Uncheck the database (i.e., open a connection to your database by passing the parameter ;shutdown=true before leaving your application).
2. Setar derby.language.sequence.preallocator=1, see that this potentially worsens competition between sequences.