I have three associated models:
House has a bidirectional OneToMany association with Person and Person has bidirectional OneToOne with PersonDetail.
When loading Person direct by Criteria or Query the PersonDetail are correctly eager loaded as defined on Annotation.
But when lazy loading the persons collection of House, many additional and unnecessary queries are triggered.
Hibernate Version 4.1.2 (previous tests on 3.6.10 given the same error)
Models:
Code:
package testehibernate4;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
/**
*
* @author andremerlo
*/
@Entity
public class House implements Serializable {
private Long id;
private List<Person> persons = new ArrayList<>();
@Id
@GeneratedValue
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
@OneToMany
public List<Person> getPersons() {
return persons;
}
public void setPersons(List<Person> persons) {
this.persons = persons;
}
public void addPerson(Person person) {
persons.add(person);
}
}
Code:
package testehibernate4;
import java.io.Serializable;
import javax.persistence.*;
import org.hibernate.annotations.Fetch;
import org.hibernate.annotations.FetchMode;
/**
*
* @author andremerlo
*/
@Entity
public class Person implements Serializable {
private Long id;
private PersonDetail detail;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
@Fetch(FetchMode.JOIN)
@OneToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
public PersonDetail getDetail() {
return detail;
}
public void setDetail(PersonDetail detail) {
this.detail = detail;
//detail.setPerson(this);
}
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Person{"
+ "id=" + id
+ ", name=" + name
+ ", detail=" + detail
+ '}';
}
}
Code:
package testehibernate4;
import java.io.Serializable;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import org.hibernate.annotations.Fetch;
import org.hibernate.annotations.FetchMode;
/**
*
* @author andremerlo
*/
@Entity
public class PersonDetail implements Serializable {
private Long id;
private Person person = new Person();
private Integer age;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
@Fetch(FetchMode.JOIN)
@OneToOne(mappedBy = "detail", optional = false, fetch = FetchType.EAGER)
public Person getPerson() {
return person;
}
public void setPerson(Person person) {
this.person = person;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "PersonDetail{" + "age=" + age + '}';
}
}
HibernateUtil for SessionFactory and test data creation:
Code:
package testehibernate4;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.jdbc.Work;
import org.hibernate.tool.hbm2ddl.SchemaExport;
/**
*
* @author andremerlo
*/
public class HibernateUtil {
private static SessionFactory factory;
public static void main(String[] args) {
buildAllReload();
}
public static SessionFactory getSessionFactory() {
if (factory == null) {
init();
}
return factory;
}
public static void init() {
Configuration config = getConfig();
try {
factory = config.buildSessionFactory();
} catch (Throwable ex) {
// Make sure you log the exception, as it might be swallowed
System.err.println("Initial SessionFactory creation failed." + ex);
throw new ExceptionInInitializerError(ex);
}
}
private static Configuration getConfig() {
Configuration config = new Configuration();
/*
* as classes mapeadas
*/
config.addAnnotatedClass(House.class);
config.addAnnotatedClass(Person.class);
config.addAnnotatedClass(PersonDetail.class);
/*
* as propriedades de configuracao do hibernate
*/
Properties props = new Properties();
props.setProperty("hibernate.dialect", "org.hibernate.dialect.MySQL5InnoDBDialect");
props.setProperty("hibernate.connection.driver_class", "com.mysql.jdbc.Driver");
props.setProperty("hibernate.connection.url", "jdbc:mysql://127.0.0.1:3306/teste_hibernate_4");
props.setProperty("hibernate.connection.username", "root");
props.setProperty("hibernate.connection.password", "1010");
props.setProperty("hibernate.show_sql", "true");
props.setProperty("hibernate.format_sql", "true");
config.addProperties(props);
return config;
}
public static void buildAllReload() {
final Configuration config = getConfig();
config.setProperty("hibernate.show_sql", "false");
try {
factory = config.buildSessionFactory();
factory.openSession().doWork(new Work() {
@Override
public void execute(final Connection conn) throws SQLException {
SchemaExport schemaExport = new SchemaExport(config, conn);
System.out.println("Criando estrutura da base");
schemaExport.create(true, true);
System.out.println("Carregando dados");
load(factory);
}
});
} catch (Throwable ex) {
// Make sure you log the exception, as it might be swallowed
System.err.println("Initial SessionFactory creation failed." + ex);
throw new ExceptionInInitializerError(ex);
}
}
public static void load(SessionFactory factory) {
Session session = factory.openSession();
Transaction tx = session.beginTransaction();
House house = new House();
Person person;
PersonDetail detail;
for (int i = 1; i <= 2; i++) {
detail = new PersonDetail();
detail.setAge(i);
person = new Person();
person.setName("JOHN-" + i);
person.setDetail(detail);
session.save(detail);
session.save(person);
house.addPerson(person);
}
session.save(house);
tx.commit();
session.close();
//*********************************************************************/
}
}
And the test code:
Code:
package testehibernate4;
import org.hibernate.Query;
import org.hibernate.Session;
/**
*
* @author andremerlo
*/
public class FetchTest {
public static void main(String[] args) {
Session s = HibernateUtil.getSessionFactory().openSession();
//get the House
Query q = s.createQuery("from House");
House h = (House) q.uniqueResult();
//iterate over person which trigger the lazy load of person collection
for (Person person : h.getPersons()) {
System.out.println(person);
}
}
}
When run FetchTest a first query returns the House.
When accessing the lazy load persons collection, iterating over it, a second query is triggered to retrieve the Persons and associated PersonDetails(in eager fetch mode), and 2 unnecessary queries to retrieve the PersonDetails again:
Code:
Hibernate:
select
house0_.id as id0_
from
House house0_
Hibernate:
select
persons0_.House_id as House1_0_3_,
persons0_.persons_id as persons2_3_,
person1_.id as id1_0_,
person1_.detail_id as detail3_1_0_,
person1_.name as name1_0_,
persondeta2_.id as id2_1_,
persondeta2_.age as age2_1_,
person3_.id as id1_2_,
person3_.detail_id as detail3_1_2_,
person3_.name as name1_2_
from
House_Person persons0_
inner join
Person person1_
on persons0_.persons_id=person1_.id
left outer join
PersonDetail persondeta2_
on person1_.detail_id=persondeta2_.id
left outer join
Person person3_
on persondeta2_.id=person3_.detail_id
where
persons0_.House_id=?
Hibernate:
select
person0_.id as id1_2_,
person0_.detail_id as detail3_1_2_,
person0_.name as name1_2_,
persondeta1_.id as id2_0_,
persondeta1_.age as age2_0_,
person2_.id as id1_1_,
person2_.detail_id as detail3_1_1_,
person2_.name as name1_1_
from
Person person0_
left outer join
PersonDetail persondeta1_
on person0_.detail_id=persondeta1_.id
left outer join
Person person2_
on persondeta1_.id=person2_.detail_id
where
person0_.detail_id=?
Hibernate:
select
person0_.id as id1_2_,
person0_.detail_id as detail3_1_2_,
person0_.name as name1_2_,
persondeta1_.id as id2_0_,
persondeta1_.age as age2_0_,
person2_.id as id1_1_,
person2_.detail_id as detail3_1_1_,
person2_.name as name1_1_
from
Person person0_
left outer join
PersonDetail persondeta1_
on person0_.detail_id=persondeta1_.id
left outer join
Person person2_
on persondeta1_.id=person2_.detail_id
where
person0_.detail_id=?
Any help will be appreciated.
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