Below is my Owning side Entity –

@Entity
@Table(name = "T_PERSON")
@Inheritance(strategy = InheritanceType.JOINED)
public class Person {

private Long id;
private String firstName;
private String lastName;    
private IdCard idCard;

public Person() {
    // TODO Auto-generated constructor stub
}

public Person(String firstName, String lastName) {
    this.firstName=firstName;
    this.lastName=lastName;
}

@Id
@GeneratedValue
public Long getId() {
    return id;
}

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

@Column(name = "FIRST_NAME")
public String getFirstName() {
    return firstName;
}

public void setFirstName(String firstName) {
    this.firstName = firstName;
}

@Column(name = "LAST_NAME")
public String getLastName() {
    return lastName;
}

public void setLastName(String lastName) {
    this.lastName = lastName;
}

@OneToOne(fetch=FetchType.LAZY)
@JoinColumn(name="ID_CARD_ID")  
public IdCard getIdCard() {
    return idCard;
}

public void setIdCard(IdCard idCard) {
    this.idCard = idCard;
}
}

Inverse side Entity –

@Entity
@Table(name = "T_ID_CARD")
public class IdCard {
private Long id;
private String idNumber;
private Date issueDate;
//private Person person;

@Id
@GeneratedValue
public Long getId() {
    return id;

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

}
@Column(name = "ID_NUMBER")
public String getIdNumber() {
    return idNumber;

}
public void setIdNumber(String idNumber) {
    this.idNumber = idNumber;

}
@Column(name = "ISSUE_DATE")
@Temporal(TemporalType.TIMESTAMP)
public Date getIssueDate() {
    return issueDate;
}
public void setIssueDate(Date issueDate) {
    this.issueDate = issueDate;
}
}

Persistence.xml –

<persistence-unit name = "RestSpringJPAPractice" transaction-type = "RESOURCE_LOCAL">
    <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider> 
    <class>com.practice.rest.spring.jpa.Person</class>
    <class>com.practice.rest.spring.jpa.Geek</class>
    <class>com.practice.rest.spring.jpa.IdCard</class>
    <exclude-unlisted-classes>true</exclude-unlisted-classes>
      
      <properties>
            <property name="javax.persistence.jdbc.driver" value="oracle.jdbc.OracleDriver" />
            <property name="javax.persistence.jdbc.url" value="jdbc:oracle:thin:@somehost:someport:somesid" />
            <property name="javax.persistence.jdbc.user" value="some_user" />
            <property name="javax.persistence.jdbc.password" value="some_pwd" />
            <property name="hibernate.dialect" value="org.hibernate.dialect.OracleDialect" />
            <property name="hibernate.show_sql" value="true"/>
            <!-- <property name="hibernate.cache.use.query_cache" value="false"/> -->
            <!-- <property name="hibernate.format_sql" value="true"/>    -->    
            <property name="hibernate.hbm2ddl.auto" value="create" />
        </properties>
   </persistence-unit>  
</persistence>

Now for below code –

TypedQuery<Person> query = entitymanager.createQuery("from Person", Person.class);
        List<Person> resultList = query.getResultList();
        for (Person person : resultList) {
            StringBuilder sb = new StringBuilder();
            sb.append(person.getFirstName()).append(" ").append(person.getLastName()).append("  ");
            IdCard idCard = person.getIdCard();
            if(idCard != null)
                sb.append(idCard.getIdNumber()).append("  ").append(person.getIdCard().getIssueDate());
}

Hibernate generates below query only –

select person0_.id as id1_2_, person0_.FIRST_NAME as first_na2_2_, person0_.ID_CARD_ID as id_card_4_2_, person0_.LAST_NAME as last_nam3_2_, person0_1_.FAV_LAN as fav_lan1_0_, decode(person0_.id, person0_1_.id, 1, 0) as clazz_ from T_PERSON person0_, T_GEEK person0_1_ where person0_.id=person0_1_.id(+)

My question –

• How and when IdCard.idNumber and IdCard.issueDate is being fetched when the above query does not include IdCard table
• why hibernate is not generating additional query for fetching IdCard when person.getIdCard(); is explicitly called
• Is IdCard is being fetched eagerly when the it is configured with FetchType.LAZY ? if so, where is the generated query?