Usage of the Hibernate @LazyCollection Annotation Article by Abdallah Sawan
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AbdallahSawan
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package com.baeldung.hibernate.lazyCollection.model;
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import org.hibernate.annotations.LazyCollection;
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import org.hibernate.annotations.LazyCollectionOption;
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import javax.persistence.*;
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import java.util.ArrayList;
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import java.util.List;
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@Entity
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public class Branch {
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@Id
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@GeneratedValue(strategy = GenerationType.IDENTITY)
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private Long id;
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private String name;
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public Branch() {
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}
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public Branch(String name) {
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this.name = name;
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}
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@OneToMany(mappedBy = "mainBranch")
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@LazyCollection(LazyCollectionOption.TRUE)
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private List<Employee> mainEmployees;
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@OneToMany(mappedBy = "subBranch")
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@LazyCollection(LazyCollectionOption.FALSE)
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private List<Employee> subEmployees;
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@OneToMany(mappedBy = "additionalBranch")
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@LazyCollection(LazyCollectionOption.EXTRA)
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@OrderColumn(name = "id")
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private List<Employee> additionalEmployees;
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public Long getId() {
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return id;
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}
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public void setId(Long id) {
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this.id = id;
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}
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public List<Employee> getMainEmployees() {
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return mainEmployees;
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}
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public void setMainEmployees(List<Employee> mainEmployees) {
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this.mainEmployees = mainEmployees;
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}
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public List<Employee> getSubEmployees() {
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return subEmployees;
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}
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public void setSubEmployees(List<Employee> subEmployees) {
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this.subEmployees = subEmployees;
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}
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public List<Employee> getAdditionalEmployees() {
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return additionalEmployees;
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}
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public void setAdditionalEmployees(List<Employee> additionalEmployees) {
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this.additionalEmployees = additionalEmployees;
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}
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public void addMainEmployee(Employee employee) {
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if (this.mainEmployees == null) {
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this.mainEmployees = new ArrayList<>();
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}
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this.mainEmployees.add(employee);
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}
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public void addSubEmployee(Employee employee) {
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if (this.subEmployees == null) {
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this.subEmployees = new ArrayList<>();
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}
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this.subEmployees.add(employee);
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}
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public void addAdditionalEmployee(Employee employee) {
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if (this.additionalEmployees == null) {
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this.additionalEmployees = new ArrayList<>();
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}
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this.additionalEmployees.add(employee);
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}
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}
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package com.baeldung.hibernate.lazyCollection.model;
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import javax.persistence.*;
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@Entity
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public class Employee {
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@Id
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@GeneratedValue(strategy = GenerationType.IDENTITY)
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private Long id;
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private String name;
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private Long rank;
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public Employee() {
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}
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public Employee(String name, Long rank, Branch mainBranch, Branch subBranch, Branch additionalBranch) {
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this.name = name;
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this.rank = rank;
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this.mainBranch = mainBranch;
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this.subBranch = subBranch;
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this.additionalBranch = additionalBranch;
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}
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@ManyToOne
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private Branch mainBranch;
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@ManyToOne
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private Branch subBranch;
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@ManyToOne
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private Branch additionalBranch;
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public Long getId() {
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return id;
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}
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public void setId(Long id) {
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this.id = id;
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}
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public Long getRank() {
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return rank;
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}
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public void setRank(Long rank) {
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this.rank = rank;
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}
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public Branch getMainBranch() {
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return mainBranch;
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}
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public void setMainBranch(Branch mainBranch) {
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this.mainBranch = mainBranch;
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}
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public Branch getSubBranch() {
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return subBranch;
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}
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public void setSubBranch(Branch subBranch) {
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this.subBranch = subBranch;
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}
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public Branch getAdditionalBranch() {
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return additionalBranch;
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}
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public void setAdditionalBranch(Branch additionalBranch) {
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this.additionalBranch = additionalBranch;
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}
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}
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@ -0,0 +1,95 @@
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package com.baeldung.hibernate.lazyCollection;
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import com.baeldung.hibernate.lazyCollection.model.Branch;
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import com.baeldung.hibernate.lazyCollection.model.Employee;
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import org.hibernate.Hibernate;
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import org.hibernate.Session;
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import org.hibernate.SessionFactory;
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import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
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import org.hibernate.cfg.Configuration;
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import org.hibernate.dialect.H2Dialect;
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import org.hibernate.service.ServiceRegistry;
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import org.junit.jupiter.api.Assertions;
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import org.junit.jupiter.api.Test;
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import org.springframework.boot.test.context.SpringBootTest;
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import javax.annotation.PostConstruct;
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@SpringBootTest
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public class LazyCollectionTests {
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private static SessionFactory sessionFactory;
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private Session session;
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Branch branch;
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@PostConstruct
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public void beforeTests() {
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Configuration configuration = new Configuration().addAnnotatedClass(Branch.class).addAnnotatedClass(Employee.class)
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.setProperty("hibernate.dialect", H2Dialect.class.getName())
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.setProperty("hibernate.connection.driver_class", org.h2.Driver.class.getName())
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.setProperty("hibernate.connection.url", "jdbc:h2:mem:test")
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.setProperty("hibernate.connection.username", "sa").setProperty("hibernate.connection.password", "")
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.setProperty("hibernate.hbm2ddl.auto", "update");
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ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
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.applySettings(configuration.getProperties()).build();
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sessionFactory = configuration.buildSessionFactory(serviceRegistry);
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setUp();
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}
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private void setUp() {
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session = sessionFactory.openSession();
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session.beginTransaction();
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branch = new Branch("Main Branch");
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session.save(branch);
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Employee mainEmployee1 = new Employee("main employee 1",1L, branch, null, null);
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Employee mainEmployee2 = new Employee("main employee 2", 2L, branch, null, null);
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Employee mainEmployee3 = new Employee("main employee 3", 3L, branch, null, null);
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session.save(mainEmployee1);
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session.save(mainEmployee2);
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session.save(mainEmployee3);
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Employee subEmployee1 = new Employee("sub employee 1", 1L, null, branch, null);
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Employee subEmployee2 = new Employee("sub employee 2", 2L, null, branch, null);
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Employee subEmployee3 = new Employee("sub employee 3", 3L, null, branch, null);
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session.save(subEmployee1);
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session.save(subEmployee2);
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session.save(subEmployee3);
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Employee additionalEmployee1 = new Employee("additional employee 1", 1L, null, null, branch);
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Employee additionalEmployee2 = new Employee("additional employee 2", 2L, null, null, branch);
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Employee additionalEmployee3 = new Employee("additional employee 3", 3L, null, null, branch);
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session.save(additionalEmployee1);
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session.save(additionalEmployee2);
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session.save(additionalEmployee3);
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session.flush();
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session.refresh(branch);
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session.getTransaction().commit();
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session.close();
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}
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@Test
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public void testLazyFetching() {
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Assertions.assertFalse(Hibernate.isInitialized(branch.getMainEmployees()));
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}
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@Test
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public void testEagerFetching() {
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Assertions.assertTrue(Hibernate.isInitialized(branch.getSubEmployees()));
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}
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@Test
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public void testExtraFetching() {
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Assertions.assertFalse(Hibernate.isInitialized(branch.getAdditionalEmployees()));
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}
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}
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