2021-08 spring-09-jpql added

2026-05-30 10:50:42 +00:00 · 2021-09-25 00:57:23 +04:00
parent 9f06ef6241
commit a02d466496
131 changed files with 4657 additions and 0 deletions
@@ -0,0 +1,4 @@
+.idea/
+*.iml
+
+target/
@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>ru.otus</groupId>
+    <artifactId>jpql-exercise</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.5.4</version>
+    </parent>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <scope>runtime</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <optional>true</optional>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+</project>
@@ -0,0 +1,13 @@
+package ru.otus.example.ormdemo;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class OrmDemoApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(OrmDemoApplication.class, args);
+	}
+
+}
@@ -0,0 +1,21 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "avatars")
+public class Avatar {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "photo_url", nullable = false, unique = true)
+    private String photoUrl;
+}
@@ -0,0 +1,21 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "courses")
+public class Course {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "name", nullable = false, unique = true)
+    private String name;
+}
@@ -0,0 +1,22 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "emails")
+public class EMail {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "email", nullable = false, unique = true)
+    private String email;
+}
@@ -0,0 +1,39 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.*;
+
+import javax.persistence.*;
+import java.util.List;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity // Указывает, что данный класс является сущностью
+@Table(name = "otus_students") // Задает имя таблицы, на которую будет отображаться сущность
+public class OtusStudent {
+    @Id // Позволяет указать какое поле является идентификатором
+    @GeneratedValue(strategy = GenerationType.IDENTITY) // Стратегия генерации идентификаторов
+    private long id;
+
+    // Задает имя и некоторые свойства поля таблицы, на которое будет отображаться поле сущности
+    @Column(name = "name", nullable = false, unique = true)
+    private String name;
+
+    // Указывает на связь между таблицами "один к одному"
+    @OneToOne(targetEntity = Avatar.class, cascade = CascadeType.ALL)
+    // Задает поле, по которому происходит объединение с таблицей для хранения связанной сущности
+    @JoinColumn(name = "avatar_id")
+    private Avatar avatar;
+
+    // Указывает на связь между таблицами "один ко многим"
+    @OneToMany(targetEntity = EMail.class, cascade = CascadeType.ALL, fetch = FetchType.EAGER)
+    @JoinColumn(name = "student_id")
+    private List<EMail> emails;
+
+    // Указывает на связь между таблицами "многие ко многим"
+    @ManyToMany(targetEntity = Course.class, fetch = FetchType.LAZY, cascade = CascadeType.ALL)
+    // Задает таблицу связей между таблицами для хранения родительской и связанной сущностью
+    @JoinTable(name = "student_courses", joinColumns = @JoinColumn(name = "student_id"),
+            inverseJoinColumns = @JoinColumn(name = "course_id"))
+    private List<Course> courses;
+}
@@ -0,0 +1,18 @@
+package ru.otus.example.ormdemo.repositories;
+
+
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface OtusStudentRepository {
+    OtusStudent save(OtusStudent student);
+    Optional<OtusStudent> findById(long id);
+
+    List<OtusStudent> findAll();
+    List<OtusStudent> findByName(String name);
+
+    void updateNameById(long id, String name);
+    void deleteById(long id);
+}
@@ -0,0 +1,58 @@
+package ru.otus.example.ormdemo.repositories;
+
+import org.springframework.stereotype.Repository;
+import org.springframework.transaction.annotation.Transactional;
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import javax.persistence.EntityManager;
+import javax.persistence.PersistenceContext;
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
+
+// @Transactional должна стоять на методе сервиса.
+// Причем, если метод не подразумевает изменения данных в БД то категорически желательно
+// выставить у аннотации параметр readOnly в true.
+// Но это только упражнение и транзакции мы пока не проходили.
+// Поэтому, для упрощения, пока вешаем над классом репозитория
+@Transactional
+@Repository
+public class OtusStudentRepositoryJpa implements OtusStudentRepository {
+
+    @PersistenceContext
+    private final EntityManager em;
+
+    public OtusStudentRepositoryJpa(EntityManager em) {
+        this.em = em;
+    }
+
+    @Override
+    public OtusStudent save(OtusStudent student) {
+        return null;
+    }
+
+    @Override
+    public Optional<OtusStudent> findById(long id) {
+        return Optional.empty();
+    }
+
+    @Override
+    public List<OtusStudent> findAll() {
+        return Collections.emptyList();
+    }
+
+    @Override
+    public List<OtusStudent> findByName(String name) {
+        return Collections.emptyList();
+    }
+
+    @Override
+    public void updateNameById(long id, String name) {
+
+    }
+
+    @Override
+    public void deleteById(long id) {
+    }
+
+}
@@ -0,0 +1,15 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:testdb
+    initialization-mode: always
+
+  jpa:
+    generate-ddl: false
+    hibernate:
+      ddl-auto: none
+
+    show-sql: true
+
+logging:
+  level:
+    ROOT: ERROR
@@ -0,0 +1,31 @@
+create table avatars(
+    id bigserial,
+    photo_url varchar(8000),
+    primary key (id)
+);
+
+create table courses(
+    id bigserial,
+    name varchar(255),
+    primary key (id)
+);
+
+create table otus_students(
+    id bigserial,
+    name varchar(255),
+    avatar_id bigint references avatars (id),
+    primary key (id)
+);
+
+create table emails(
+    id bigserial,
+    student_id bigint references otus_students(id) on delete cascade,
+    email varchar(255),
+    primary key (id)
+);
+
+create table student_courses(
+    student_id bigint references otus_students(id) on delete cascade,
+    course_id bigint references courses(id),
+    primary key (student_id, course_id)
+);
@@ -0,0 +1,126 @@
+package ru.otus.example.ormdemo.repositories;
+
+import lombok.val;
+import org.hibernate.SessionFactory;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
+import org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManager;
+import org.springframework.context.annotation.Import;
+import ru.otus.example.ormdemo.models.OtusStudent;
+import ru.otus.example.ormdemo.models.Avatar;
+import ru.otus.example.ormdemo.models.Course;
+import ru.otus.example.ormdemo.models.EMail;
+
+import java.util.Collections;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@DisplayName("Репозиторий на основе Jpa для работы со студентами ")
+@DataJpaTest
+@Import(OtusStudentRepositoryJpa.class)
+class OtusStudentRepositoryJpaTest {
+
+    private static final int EXPECTED_NUMBER_OF_STUDENTS = 10;
+    private static final long FIRST_STUDENT_ID = 1L;
+    private static final String FIRST_STUDENT_NAME = "student_01";
+
+    private static final int EXPECTED_QUERIES_COUNT = 31;
+
+    private static final String STUDENT_AVATAR_URL = "где-то там";
+    private static final String STUDENT_EMAIL = "any@mail.com";
+    private static final String COURSE_NAME = "Spring";
+    private static final String STUDENT_NAME = "Вася";
+
+    @Autowired
+    private OtusStudentRepositoryJpa repositoryJpa;
+
+    @Autowired
+    private TestEntityManager em;
+
+    @DisplayName(" должен загружать информацию о нужном студенте по его id")
+    @Test
+    void shouldFindExpectedStudentById() {
+        val optionalActualStudent = repositoryJpa.findById(FIRST_STUDENT_ID);
+        val expectedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        assertThat(optionalActualStudent).isPresent().get()
+                .usingRecursiveComparison().isEqualTo(expectedStudent);
+    }
+
+    @DisplayName("должен загружать список всех студентов с полной информацией о них")
+    @Test
+    void shouldReturnCorrectStudentsListWithAllInfo() {
+        SessionFactory sessionFactory = em.getEntityManager().getEntityManagerFactory()
+                .unwrap(SessionFactory.class);
+        sessionFactory.getStatistics().setStatisticsEnabled(true);
+
+
+        System.out.println("\n\n\n\n----------------------------------------------------------------------------------------------------------");
+        val students = repositoryJpa.findAll();
+        assertThat(students).isNotNull().hasSize(EXPECTED_NUMBER_OF_STUDENTS)
+                .allMatch(s -> !s.getName().equals(""))
+                .allMatch(s -> s.getCourses() != null && s.getCourses().size() > 0)
+                .allMatch(s -> s.getAvatar() != null)
+                .allMatch(s -> s.getEmails() != null && s.getEmails().size() > 0);
+        System.out.println("----------------------------------------------------------------------------------------------------------\n\n\n\n");
+        assertThat(sessionFactory.getStatistics().getPrepareStatementCount()).isEqualTo(EXPECTED_QUERIES_COUNT);
+    }
+
+    @DisplayName(" должен корректно сохранять всю информацию о студенте")
+    @Test
+    void shouldSaveAllStudentInfo() {
+        val avatar = new Avatar(0, STUDENT_AVATAR_URL);
+        val email = new EMail(0, STUDENT_EMAIL);
+        val emails = Collections.singletonList(email);
+
+        val course = new Course(0, COURSE_NAME);
+        val courses = Collections.singletonList(course);
+
+
+        val vasya = new OtusStudent(0, STUDENT_NAME, avatar, emails, courses);
+        repositoryJpa.save(vasya);
+        assertThat(vasya.getId()).isGreaterThan(0);
+
+        val actualStudent = em.find(OtusStudent.class, vasya.getId());
+        assertThat(actualStudent).isNotNull().matches(s -> !s.getName().equals(""))
+                .matches(s -> s.getCourses() != null && s.getCourses().size() > 0 && s.getCourses().get(0).getId() > 0)
+                .matches(s -> s.getAvatar() != null)
+                .matches(s -> s.getEmails() != null && s.getEmails().size() > 0);
+    }
+
+    @DisplayName(" должен загружать информацию о нужном студенте по его имени")
+    @Test
+    void shouldFindExpectedStudentByName() {
+        val firstStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        List<OtusStudent> students = repositoryJpa.findByName(FIRST_STUDENT_NAME);
+        assertThat(students).containsOnlyOnce(firstStudent);
+    }
+
+    @DisplayName(" должен изменять имя заданного студента по его id")
+    @Test
+    void shouldUpdateStudentNameById() {
+        val firstStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        String oldName = firstStudent.getName();
+        em.detach(firstStudent);
+
+        repositoryJpa.updateNameById(FIRST_STUDENT_ID, STUDENT_NAME);
+        val updatedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+
+        assertThat(updatedStudent.getName()).isNotEqualTo(oldName).isEqualTo(STUDENT_NAME);
+    }
+
+    @DisplayName(" должен удалять заданного студента по его id")
+    @Test
+    void shouldDeleteStudentNameById() {
+        val firstStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        assertThat(firstStudent).isNotNull();
+        em.detach(firstStudent);
+
+        repositoryJpa.deleteById(FIRST_STUDENT_ID);
+        val deletedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+
+        assertThat(deletedStudent).isNull();
+    }
+}
@@ -0,0 +1,17 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:testdb
+    initialization-mode: always
+
+  jpa:
+    generate-ddl: false
+    #generate-ddl: true
+    hibernate:
+      ddl-auto: none
+      #ddl-auto: create-drop
+
+    #show-sql: true
+
+logging:
+  level:
+    ROOT: ERROR
@@ -0,0 +1,29 @@
+insert into avatars(photo_url)
+values ('photoUrl_01'), ('photoUrl_02'), ('photoUrl_03'), ('photoUrl_04'), ('photoUrl_05'),
+       ('photoUrl_06'), ('photoUrl_07'), ('photoUrl_08'), ('photoUrl_09'), ('photoUrl_10');
+
+insert into courses(name)
+values ('course_name_01'), ('course_name_02'), ('course_name_03'), ('course_name_04'), ('course_name_05'),
+       ('course_name_06'), ('course_name_07'), ('course_name_08'), ('course_name_09'), ('course_name_10'), ('not_used_11');
+
+insert into otus_students(name, avatar_id)
+values ('student_01', 1), ('student_02', 2), ('student_03', 3), ('student_04', 4), ('student_05', 5),
+       ('student_06', 6), ('student_07', 7), ('student_08', 8), ('student_09', 9), ('student_10', 10);
+
+
+insert into emails(email, student_id)
+values ('email_01', 1), ('email_02', 1), ('email_03', 2), ('email_04', 2), ('email_05', 3), ('email_06', 4),
+       ('email_07', 5), ('email_08', 6), ('email_09', 7), ('email_10', 8), ('email_11', 9), ('email_12', 10);
+
+
+insert into student_courses(student_id, course_id)
+values (1, 1),   (1, 2),   (1, 3),
+       (2, 2),   (2, 4),   (2, 5),
+       (3, 3),   (3, 6),   (3, 7),
+       (4, 4),   (4, 8),   (4, 9),
+       (5, 5),   (5, 10),  (5, 1),
+       (6, 6),   (6, 2),   (6, 3),
+       (7, 7),   (7, 4),   (7, 5),
+       (8, 8),   (8, 6),   (8, 7),
+       (9, 9),   (9, 8),   (9, 10),
+       (10, 10), (10, 1),  (10, 2);
@@ -0,0 +1,4 @@
+.idea/
+*.iml
+
+target/
@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>ru.otus</groupId>
+    <artifactId>jpql-solution-01</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.5.4</version>
+    </parent>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <scope>runtime</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <optional>true</optional>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+</project>
@@ -0,0 +1,13 @@
+package ru.otus.example.ormdemo;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class OrmDemoApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(OrmDemoApplication.class, args);
+	}
+
+}
@@ -0,0 +1,21 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "avatars")
+public class Avatar {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "photo_url", nullable = false, unique = true)
+    private String photoUrl;
+}
@@ -0,0 +1,21 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "courses")
+public class Course {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "name", nullable = false, unique = true)
+    private String name;
+}
@@ -0,0 +1,22 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "emails")
+public class EMail {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "email", nullable = false, unique = true)
+    private String email;
+}
@@ -0,0 +1,39 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.*;
+
+import javax.persistence.*;
+import java.util.List;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity // Указывает, что данный класс является сущностью
+@Table(name = "otus_students") // Задает имя таблицы, на которую будет отображаться сущность
+public class OtusStudent {
+    @Id // Позволяет указать какое поле является идентификатором
+    @GeneratedValue(strategy = GenerationType.IDENTITY) // Стратегия генерации идентификаторов
+    private long id;
+
+    // Задает имя и некоторые свойства поля таблицы, на которое будет отображаться поле сущности
+    @Column(name = "name", nullable = false, unique = true)
+    private String name;
+
+    // Указывает на связь между таблицами "один к одному"
+    @OneToOne(targetEntity = Avatar.class, cascade = CascadeType.ALL)
+    // Задает поле, по которому происходит объединение с таблицей для хранения связанной сущности
+    @JoinColumn(name = "avatar_id")
+    private Avatar avatar;
+
+    // Указывает на связь между таблицами "один ко многим"
+    @OneToMany(targetEntity = EMail.class, cascade = CascadeType.ALL, fetch = FetchType.EAGER)
+    @JoinColumn(name = "student_id")
+    private List<EMail> emails;
+
+    // Указывает на связь между таблицами "многие ко многим"
+    @ManyToMany(targetEntity = Course.class, fetch = FetchType.LAZY, cascade = CascadeType.ALL)
+    // Задает таблицу связей между таблицами для хранения родительской и связанной сущностью
+    @JoinTable(name = "student_courses", joinColumns = @JoinColumn(name = "student_id"),
+            inverseJoinColumns = @JoinColumn(name = "course_id"))
+    private List<Course> courses;
+}
@@ -0,0 +1,18 @@
+package ru.otus.example.ormdemo.repositories;
+
+
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface OtusStudentRepository {
+    OtusStudent save(OtusStudent student);
+    Optional<OtusStudent> findById(long id);
+
+    List<OtusStudent> findAll();
+    List<OtusStudent> findByName(String name);
+
+    void updateNameById(long id, String name);
+    void deleteById(long id);
+}
@@ -0,0 +1,64 @@
+package ru.otus.example.ormdemo.repositories;
+
+import org.springframework.stereotype.Repository;
+import org.springframework.transaction.annotation.Transactional;
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import javax.persistence.EntityManager;
+import javax.persistence.PersistenceContext;
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
+
+// @Transactional должна стоять на методе сервиса.
+// Причем, если метод не подразумевает изменения данных в БД то категорически желательно
+// выставить у аннотации параметр readOnly в true.
+// Но это только упражнение и транзакции мы пока не проходили.
+// Поэтому, для упрощения, пока вешаем над классом репозитория
+@Transactional
+@Repository
+public class OtusStudentRepositoryJpa implements OtusStudentRepository {
+
+    @PersistenceContext
+    private final EntityManager em;
+
+    public OtusStudentRepositoryJpa(EntityManager em) {
+        this.em = em;
+    }
+
+    @Override
+    public OtusStudent save(OtusStudent student) {
+        if (student.getId() <= 0) {
+            em.persist(student);
+            return student;
+        } else {
+            return em.merge(student);
+        }
+    }
+
+    @Override
+    public Optional<OtusStudent> findById(long id) {
+        return Optional.ofNullable(em.find(OtusStudent.class, id));
+    }
+
+    @Override
+    public List<OtusStudent> findAll() {
+        return Collections.emptyList();
+    }
+
+    @Override
+    public List<OtusStudent> findByName(String name) {
+        return Collections.emptyList();
+    }
+
+    @Override
+    public void updateNameById(long id, String name) {
+
+    }
+
+    @Override
+    public void deleteById(long id) {
+
+    }
+
+}
@@ -0,0 +1,15 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:testdb
+    initialization-mode: always
+
+  jpa:
+    generate-ddl: false
+    hibernate:
+      ddl-auto: none
+
+    show-sql: true
+
+logging:
+  level:
+    ROOT: ERROR
@@ -0,0 +1,31 @@
+create table avatars(
+    id bigserial,
+    photo_url varchar(8000),
+    primary key (id)
+);
+
+create table courses(
+    id bigserial,
+    name varchar(255),
+    primary key (id)
+);
+
+create table otus_students(
+    id bigserial,
+    name varchar(255),
+    avatar_id bigint references avatars (id),
+    primary key (id)
+);
+
+create table emails(
+    id bigserial,
+    student_id bigint references otus_students(id) on delete cascade,
+    email varchar(255),
+    primary key (id)
+);
+
+create table student_courses(
+    student_id bigint references otus_students(id) on delete cascade,
+    course_id bigint references courses(id),
+    primary key (student_id, course_id)
+);
@@ -0,0 +1,126 @@
+package ru.otus.example.ormdemo.repositories;
+
+import lombok.val;
+import org.hibernate.SessionFactory;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
+import org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManager;
+import org.springframework.context.annotation.Import;
+import ru.otus.example.ormdemo.models.OtusStudent;
+import ru.otus.example.ormdemo.models.Avatar;
+import ru.otus.example.ormdemo.models.Course;
+import ru.otus.example.ormdemo.models.EMail;
+
+import java.util.Collections;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@DisplayName("Репозиторий на основе Jpa для работы со студентами ")
+@DataJpaTest
+@Import(OtusStudentRepositoryJpa.class)
+class OtusStudentRepositoryJpaTest {
+
+    private static final int EXPECTED_NUMBER_OF_STUDENTS = 10;
+    private static final long FIRST_STUDENT_ID = 1L;
+    private static final String FIRST_STUDENT_NAME = "student_01";
+
+    private static final int EXPECTED_QUERIES_COUNT = 31;
+
+    private static final String STUDENT_AVATAR_URL = "где-то там";
+    private static final String STUDENT_EMAIL = "any@mail.com";
+    private static final String COURSE_NAME = "Spring";
+    private static final String STUDENT_NAME = "Вася";
+
+    @Autowired
+    private OtusStudentRepositoryJpa repositoryJpa;
+
+    @Autowired
+    private TestEntityManager em;
+
+    @DisplayName(" должен загружать информацию о нужном студенте по его id")
+    @Test
+    void shouldFindExpectedStudentById() {
+        val optionalActualStudent = repositoryJpa.findById(FIRST_STUDENT_ID);
+        val expectedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        assertThat(optionalActualStudent).isPresent().get()
+                .usingRecursiveComparison().isEqualTo(expectedStudent);
+    }
+
+    @DisplayName("должен загружать список всех студентов с полной информацией о них")
+    @Test
+    void shouldReturnCorrectStudentsListWithAllInfo() {
+        SessionFactory sessionFactory = em.getEntityManager().getEntityManagerFactory()
+                .unwrap(SessionFactory.class);
+        sessionFactory.getStatistics().setStatisticsEnabled(true);
+
+
+        System.out.println("\n\n\n\n----------------------------------------------------------------------------------------------------------");
+        val students = repositoryJpa.findAll();
+        assertThat(students).isNotNull().hasSize(EXPECTED_NUMBER_OF_STUDENTS)
+                .allMatch(s -> !s.getName().equals(""))
+                .allMatch(s -> s.getCourses() != null && s.getCourses().size() > 0)
+                .allMatch(s -> s.getAvatar() != null)
+                .allMatch(s -> s.getEmails() != null && s.getEmails().size() > 0);
+        System.out.println("----------------------------------------------------------------------------------------------------------\n\n\n\n");
+        assertThat(sessionFactory.getStatistics().getPrepareStatementCount()).isEqualTo(EXPECTED_QUERIES_COUNT);
+    }
+
+    @DisplayName(" должен корректно сохранять всю информацию о студенте")
+    @Test
+    void shouldSaveAllStudentInfo() {
+        val avatar = new Avatar(0, STUDENT_AVATAR_URL);
+        val email = new EMail(0, STUDENT_EMAIL);
+        val emails = Collections.singletonList(email);
+
+        val course = new Course(0, COURSE_NAME);
+        val courses = Collections.singletonList(course);
+
+
+        val vasya = new OtusStudent(0, STUDENT_NAME, avatar, emails, courses);
+        repositoryJpa.save(vasya);
+        assertThat(vasya.getId()).isGreaterThan(0);
+
+        val actualStudent = em.find(OtusStudent.class, vasya.getId());
+        assertThat(actualStudent).isNotNull().matches(s -> !s.getName().equals(""))
+                .matches(s -> s.getCourses() != null && s.getCourses().size() > 0 && s.getCourses().get(0).getId() > 0)
+                .matches(s -> s.getAvatar() != null)
+                .matches(s -> s.getEmails() != null && s.getEmails().size() > 0);
+    }
+
+    @DisplayName(" должен загружать информацию о нужном студенте по его имени")
+    @Test
+    void shouldFindExpectedStudentByName() {
+        val firstStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        List<OtusStudent> students = repositoryJpa.findByName(FIRST_STUDENT_NAME);
+        assertThat(students).containsOnlyOnce(firstStudent);
+    }
+
+    @DisplayName(" должен изменять имя заданного студента по его id")
+    @Test
+    void shouldUpdateStudentNameById() {
+        val firstStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        String oldName = firstStudent.getName();
+        em.detach(firstStudent);
+
+        repositoryJpa.updateNameById(FIRST_STUDENT_ID, STUDENT_NAME);
+        val updatedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+
+        assertThat(updatedStudent.getName()).isNotEqualTo(oldName).isEqualTo(STUDENT_NAME);
+    }
+
+    @DisplayName(" должен удалять заданного студента по его id")
+    @Test
+    void shouldDeleteStudentNameById() {
+        val firstStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        assertThat(firstStudent).isNotNull();
+        em.detach(firstStudent);
+
+        repositoryJpa.deleteById(FIRST_STUDENT_ID);
+        val deletedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+
+        assertThat(deletedStudent).isNull();
+    }
+}
@@ -0,0 +1,17 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:testdb
+    initialization-mode: always
+
+  jpa:
+    generate-ddl: false
+    #generate-ddl: true
+    hibernate:
+      ddl-auto: none
+      #ddl-auto: create-drop
+
+    #show-sql: true
+
+logging:
+  level:
+    ROOT: ERROR
@@ -0,0 +1,29 @@
+insert into avatars(photo_url)
+values ('photoUrl_01'), ('photoUrl_02'), ('photoUrl_03'), ('photoUrl_04'), ('photoUrl_05'),
+       ('photoUrl_06'), ('photoUrl_07'), ('photoUrl_08'), ('photoUrl_09'), ('photoUrl_10');
+
+insert into courses(name)
+values ('course_name_01'), ('course_name_02'), ('course_name_03'), ('course_name_04'), ('course_name_05'),
+       ('course_name_06'), ('course_name_07'), ('course_name_08'), ('course_name_09'), ('course_name_10'), ('not_used_11');
+
+insert into otus_students(name, avatar_id)
+values ('student_01', 1), ('student_02', 2), ('student_03', 3), ('student_04', 4), ('student_05', 5),
+       ('student_06', 6), ('student_07', 7), ('student_08', 8), ('student_09', 9), ('student_10', 10);
+
+
+insert into emails(email, student_id)
+values ('email_01', 1), ('email_02', 1), ('email_03', 2), ('email_04', 2), ('email_05', 3), ('email_06', 4),
+       ('email_07', 5), ('email_08', 6), ('email_09', 7), ('email_10', 8), ('email_11', 9), ('email_12', 10);
+
+
+insert into student_courses(student_id, course_id)
+values (1, 1),   (1, 2),   (1, 3),
+       (2, 2),   (2, 4),   (2, 5),
+       (3, 3),   (3, 6),   (3, 7),
+       (4, 4),   (4, 8),   (4, 9),
+       (5, 5),   (5, 10),  (5, 1),
+       (6, 6),   (6, 2),   (6, 3),
+       (7, 7),   (7, 4),   (7, 5),
+       (8, 8),   (8, 6),   (8, 7),
+       (9, 9),   (9, 8),   (9, 10),
+       (10, 10), (10, 1),  (10, 2);
@@ -0,0 +1,4 @@
+.idea/
+*.iml
+
+target/
@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>ru.otus</groupId>
+    <artifactId>jpql-solution-02</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.5.4</version>
+    </parent>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <scope>runtime</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <optional>true</optional>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+</project>
@@ -0,0 +1,13 @@
+package ru.otus.example.ormdemo;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class OrmDemoApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(OrmDemoApplication.class, args);
+	}
+
+}
@@ -0,0 +1,21 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "avatars")
+public class Avatar {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "photo_url", nullable = false, unique = true)
+    private String photoUrl;
+}
@@ -0,0 +1,21 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "courses")
+public class Course {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "name", nullable = false, unique = true)
+    private String name;
+}
@@ -0,0 +1,22 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "emails")
+public class EMail {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "email", nullable = false, unique = true)
+    private String email;
+}
@@ -0,0 +1,39 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.*;
+
+import javax.persistence.*;
+import java.util.List;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity // Указывает, что данный класс является сущностью
+@Table(name = "otus_students") // Задает имя таблицы, на которую будет отображаться сущность
+public class OtusStudent {
+    @Id // Позволяет указать какое поле является идентификатором
+    @GeneratedValue(strategy = GenerationType.IDENTITY) // Стратегия генерации идентификаторов
+    private long id;
+
+    // Задает имя и некоторые свойства поля таблицы, на которое будет отображаться поле сущности
+    @Column(name = "name", nullable = false, unique = true)
+    private String name;
+
+    // Указывает на связь между таблицами "один к одному"
+    @OneToOne(targetEntity = Avatar.class, cascade = CascadeType.ALL)
+    // Задает поле, по которому происходит объединение с таблицей для хранения связанной сущности
+    @JoinColumn(name = "avatar_id")
+    private Avatar avatar;
+
+    // Указывает на связь между таблицами "один ко многим"
+    @OneToMany(targetEntity = EMail.class, cascade = CascadeType.ALL, fetch = FetchType.EAGER)
+    @JoinColumn(name = "student_id")
+    private List<EMail> emails;
+
+    // Указывает на связь между таблицами "многие ко многим"
+    @ManyToMany(targetEntity = Course.class, fetch = FetchType.LAZY, cascade = CascadeType.ALL)
+    // Задает таблицу связей между таблицами для хранения родительской и связанной сущностью
+    @JoinTable(name = "student_courses", joinColumns = @JoinColumn(name = "student_id"),
+            inverseJoinColumns = @JoinColumn(name = "course_id"))
+    private List<Course> courses;
+}
@@ -0,0 +1,18 @@
+package ru.otus.example.ormdemo.repositories;
+
+
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface OtusStudentRepository {
+    OtusStudent save(OtusStudent student);
+    Optional<OtusStudent> findById(long id);
+
+    List<OtusStudent> findAll();
+    List<OtusStudent> findByName(String name);
+
+    void updateNameById(long id, String name);
+    void deleteById(long id);
+}
@@ -0,0 +1,70 @@
+package ru.otus.example.ormdemo.repositories;
+
+import org.springframework.stereotype.Repository;
+import org.springframework.transaction.annotation.Transactional;
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import javax.persistence.EntityManager;
+import javax.persistence.PersistenceContext;
+import javax.persistence.TypedQuery;
+import java.util.List;
+import java.util.Optional;
+
+// @Transactional должна стоять на методе сервиса.
+// Причем, если метод не подразумевает изменения данных в БД то категорически желательно
+// выставить у аннотации параметр readOnly в true.
+// Но это только упражнение и транзакции мы пока не проходили.
+// Поэтому, для упрощения, пока вешаем над классом репозитория
+@Transactional
+@Repository
+public class OtusStudentRepositoryJpa implements OtusStudentRepository {
+
+    @PersistenceContext
+    private final EntityManager em;
+
+    public OtusStudentRepositoryJpa(EntityManager em) {
+        this.em = em;
+    }
+
+    @Override
+    public OtusStudent save(OtusStudent student) {
+        if (student.getId() <= 0) {
+            em.persist(student);
+            return student;
+        } else {
+            return em.merge(student);
+        }
+    }
+
+    @Override
+    public Optional<OtusStudent> findById(long id) {
+        return Optional.ofNullable(em.find(OtusStudent.class, id));
+    }
+
+    @Override
+    public List<OtusStudent> findAll() {
+        return em.createQuery("select s from OtusStudent s", OtusStudent.class)
+                .getResultList();
+    }
+
+    @Override
+    public List<OtusStudent> findByName(String name) {
+        TypedQuery<OtusStudent> query = em.createQuery("select s " +
+                        "from OtusStudent s " +
+                        "where s.name = :name",
+                OtusStudent.class);
+        query.setParameter("name", name);
+        return query.getResultList();
+    }
+
+    @Override
+    public void updateNameById(long id, String name) {
+
+    }
+
+    @Override
+    public void deleteById(long id) {
+
+    }
+
+}
@@ -0,0 +1,15 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:testdb
+    initialization-mode: always
+
+  jpa:
+    generate-ddl: false
+    hibernate:
+      ddl-auto: none
+
+    show-sql: true
+
+logging:
+  level:
+    ROOT: ERROR
@@ -0,0 +1,31 @@
+create table avatars(
+    id bigserial,
+    photo_url varchar(8000),
+    primary key (id)
+);
+
+create table courses(
+    id bigserial,
+    name varchar(255),
+    primary key (id)
+);
+
+create table otus_students(
+    id bigserial,
+    name varchar(255),
+    avatar_id bigint references avatars (id),
+    primary key (id)
+);
+
+create table emails(
+    id bigserial,
+    student_id bigint references otus_students(id) on delete cascade,
+    email varchar(255),
+    primary key (id)
+);
+
+create table student_courses(
+    student_id bigint references otus_students(id) on delete cascade,
+    course_id bigint references courses(id),
+    primary key (student_id, course_id)
+);
@@ -0,0 +1,126 @@
+package ru.otus.example.ormdemo.repositories;
+
+import lombok.val;
+import org.hibernate.SessionFactory;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
+import org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManager;
+import org.springframework.context.annotation.Import;
+import ru.otus.example.ormdemo.models.OtusStudent;
+import ru.otus.example.ormdemo.models.Avatar;
+import ru.otus.example.ormdemo.models.Course;
+import ru.otus.example.ormdemo.models.EMail;
+
+import java.util.Collections;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@DisplayName("Репозиторий на основе Jpa для работы со студентами ")
+@DataJpaTest
+@Import(OtusStudentRepositoryJpa.class)
+class OtusStudentRepositoryJpaTest {
+
+    private static final int EXPECTED_NUMBER_OF_STUDENTS = 10;
+    private static final long FIRST_STUDENT_ID = 1L;
+    private static final String FIRST_STUDENT_NAME = "student_01";
+
+    private static final int EXPECTED_QUERIES_COUNT = 31;
+
+    private static final String STUDENT_AVATAR_URL = "где-то там";
+    private static final String STUDENT_EMAIL = "any@mail.com";
+    private static final String COURSE_NAME = "Spring";
+    private static final String STUDENT_NAME = "Вася";
+
+    @Autowired
+    private OtusStudentRepositoryJpa repositoryJpa;
+
+    @Autowired
+    private TestEntityManager em;
+
+    @DisplayName(" должен загружать информацию о нужном студенте по его id")
+    @Test
+    void shouldFindExpectedStudentById() {
+        val optionalActualStudent = repositoryJpa.findById(FIRST_STUDENT_ID);
+        val expectedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        assertThat(optionalActualStudent).isPresent().get()
+                .usingRecursiveComparison().isEqualTo(expectedStudent);
+    }
+
+    @DisplayName("должен загружать список всех студентов с полной информацией о них")
+    @Test
+    void shouldReturnCorrectStudentsListWithAllInfo() {
+        SessionFactory sessionFactory = em.getEntityManager().getEntityManagerFactory()
+                .unwrap(SessionFactory.class);
+        sessionFactory.getStatistics().setStatisticsEnabled(true);
+
+
+        System.out.println("\n\n\n\n----------------------------------------------------------------------------------------------------------");
+        val students = repositoryJpa.findAll();
+        assertThat(students).isNotNull().hasSize(EXPECTED_NUMBER_OF_STUDENTS)
+                .allMatch(s -> !s.getName().equals(""))
+                .allMatch(s -> s.getCourses() != null && s.getCourses().size() > 0)
+                .allMatch(s -> s.getAvatar() != null)
+                .allMatch(s -> s.getEmails() != null && s.getEmails().size() > 0);
+        System.out.println("----------------------------------------------------------------------------------------------------------\n\n\n\n");
+        assertThat(sessionFactory.getStatistics().getPrepareStatementCount()).isEqualTo(EXPECTED_QUERIES_COUNT);
+    }
+
+    @DisplayName(" должен корректно сохранять всю информацию о студенте")
+    @Test
+    void shouldSaveAllStudentInfo() {
+        val avatar = new Avatar(0, STUDENT_AVATAR_URL);
+        val email = new EMail(0, STUDENT_EMAIL);
+        val emails = Collections.singletonList(email);
+
+        val course = new Course(0, COURSE_NAME);
+        val courses = Collections.singletonList(course);
+
+
+        val vasya = new OtusStudent(0, STUDENT_NAME, avatar, emails, courses);
+        repositoryJpa.save(vasya);
+        assertThat(vasya.getId()).isGreaterThan(0);
+
+        val actualStudent = em.find(OtusStudent.class, vasya.getId());
+        assertThat(actualStudent).isNotNull().matches(s -> !s.getName().equals(""))
+                .matches(s -> s.getCourses() != null && s.getCourses().size() > 0 && s.getCourses().get(0).getId() > 0)
+                .matches(s -> s.getAvatar() != null)
+                .matches(s -> s.getEmails() != null && s.getEmails().size() > 0);
+    }
+
+    @DisplayName(" должен загружать информацию о нужном студенте по его имени")
+    @Test
+    void shouldFindExpectedStudentByName() {
+        val firstStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        List<OtusStudent> students = repositoryJpa.findByName(FIRST_STUDENT_NAME);
+        assertThat(students).containsOnlyOnce(firstStudent);
+    }
+
+    @DisplayName(" должен изменять имя заданного студента по его id")
+    @Test
+    void shouldUpdateStudentNameById() {
+        val firstStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        String oldName = firstStudent.getName();
+        em.detach(firstStudent);
+
+        repositoryJpa.updateNameById(FIRST_STUDENT_ID, STUDENT_NAME);
+        val updatedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+
+        assertThat(updatedStudent.getName()).isNotEqualTo(oldName).isEqualTo(STUDENT_NAME);
+    }
+
+    @DisplayName(" должен удалять заданного студента по его id")
+    @Test
+    void shouldDeleteStudentNameById() {
+        val firstStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        assertThat(firstStudent).isNotNull();
+        em.detach(firstStudent);
+
+        repositoryJpa.deleteById(FIRST_STUDENT_ID);
+        val deletedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+
+        assertThat(deletedStudent).isNull();
+    }
+}
@@ -0,0 +1,17 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:testdb
+    initialization-mode: always
+
+  jpa:
+    generate-ddl: false
+    #generate-ddl: true
+    hibernate:
+      ddl-auto: none
+      #ddl-auto: create-drop
+
+    #show-sql: true
+
+logging:
+  level:
+    ROOT: ERROR
@@ -0,0 +1,29 @@
+insert into avatars(photo_url)
+values ('photoUrl_01'), ('photoUrl_02'), ('photoUrl_03'), ('photoUrl_04'), ('photoUrl_05'),
+       ('photoUrl_06'), ('photoUrl_07'), ('photoUrl_08'), ('photoUrl_09'), ('photoUrl_10');
+
+insert into courses(name)
+values ('course_name_01'), ('course_name_02'), ('course_name_03'), ('course_name_04'), ('course_name_05'),
+       ('course_name_06'), ('course_name_07'), ('course_name_08'), ('course_name_09'), ('course_name_10'), ('not_used_11');
+
+insert into otus_students(name, avatar_id)
+values ('student_01', 1), ('student_02', 2), ('student_03', 3), ('student_04', 4), ('student_05', 5),
+       ('student_06', 6), ('student_07', 7), ('student_08', 8), ('student_09', 9), ('student_10', 10);
+
+
+insert into emails(email, student_id)
+values ('email_01', 1), ('email_02', 1), ('email_03', 2), ('email_04', 2), ('email_05', 3), ('email_06', 4),
+       ('email_07', 5), ('email_08', 6), ('email_09', 7), ('email_10', 8), ('email_11', 9), ('email_12', 10);
+
+
+insert into student_courses(student_id, course_id)
+values (1, 1),   (1, 2),   (1, 3),
+       (2, 2),   (2, 4),   (2, 5),
+       (3, 3),   (3, 6),   (3, 7),
+       (4, 4),   (4, 8),   (4, 9),
+       (5, 5),   (5, 10),  (5, 1),
+       (6, 6),   (6, 2),   (6, 3),
+       (7, 7),   (7, 4),   (7, 5),
+       (8, 8),   (8, 6),   (8, 7),
+       (9, 9),   (9, 8),   (9, 10),
+       (10, 10), (10, 1),  (10, 2);
@@ -0,0 +1,4 @@
+.idea/
+*.iml
+
+target/
@@ -0,0 +1,56 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>ru.otus</groupId>
+    <artifactId>jpql-solution-03</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.5.4</version>
+    </parent>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <scope>runtime</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <optional>true</optional>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+</project>
@@ -0,0 +1,13 @@
+package ru.otus.example.ormdemo;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class OrmDemoApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(OrmDemoApplication.class, args);
+	}
+
+}
@@ -0,0 +1,21 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "avatars")
+public class Avatar {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "photo_url", nullable = false, unique = true)
+    private String photoUrl;
+}
@@ -0,0 +1,21 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "courses")
+public class Course {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "name", nullable = false, unique = true)
+    private String name;
+}
@@ -0,0 +1,22 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "emails")
+public class EMail {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "email", nullable = false, unique = true)
+    private String email;
+}
@@ -0,0 +1,39 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.*;
+
+import javax.persistence.*;
+import java.util.List;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity // Указывает, что данный класс является сущностью
+@Table(name = "otus_students") // Задает имя таблицы, на которую будет отображаться сущность
+public class OtusStudent {
+    @Id // Позволяет указать какое поле является идентификатором
+    @GeneratedValue(strategy = GenerationType.IDENTITY) // Стратегия генерации идентификаторов
+    private long id;
+
+    // Задает имя и некоторые свойства поля таблицы, на которое будет отображаться поле сущности
+    @Column(name = "name", nullable = false, unique = true)
+    private String name;
+
+    // Указывает на связь между таблицами "один к одному"
+    @OneToOne(targetEntity = Avatar.class, cascade = CascadeType.ALL)
+    // Задает поле, по которому происходит объединение с таблицей для хранения связанной сущности
+    @JoinColumn(name = "avatar_id")
+    private Avatar avatar;
+
+    // Указывает на связь между таблицами "один ко многим"
+    @OneToMany(targetEntity = EMail.class, cascade = CascadeType.ALL, fetch = FetchType.EAGER)
+    @JoinColumn(name = "student_id")
+    private List<EMail> emails;
+
+    // Указывает на связь между таблицами "многие ко многим"
+    @ManyToMany(targetEntity = Course.class, fetch = FetchType.LAZY, cascade = CascadeType.ALL)
+    // Задает таблицу связей между таблицами для хранения родительской и связанной сущностью
+    @JoinTable(name = "student_courses", joinColumns = @JoinColumn(name = "student_id"),
+            inverseJoinColumns = @JoinColumn(name = "course_id"))
+    private List<Course> courses;
+}
@@ -0,0 +1,18 @@
+package ru.otus.example.ormdemo.repositories;
+
+
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface OtusStudentRepository {
+    OtusStudent save(OtusStudent student);
+    Optional<OtusStudent> findById(long id);
+
+    List<OtusStudent> findAll();
+    List<OtusStudent> findByName(String name);
+
+    void updateNameById(long id, String name);
+    void deleteById(long id);
+}
@@ -0,0 +1,76 @@
+package ru.otus.example.ormdemo.repositories;
+
+import org.springframework.stereotype.Repository;
+import org.springframework.transaction.annotation.Transactional;
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import javax.persistence.EntityManager;
+import javax.persistence.PersistenceContext;
+import javax.persistence.Query;
+import javax.persistence.TypedQuery;
+import java.util.List;
+import java.util.Optional;
+
+// @Transactional должна стоять на методе сервиса.
+// Причем, если метод не подразумевает изменения данных в БД то категорически желательно
+// выставить у аннотации параметр readOnly в true.
+// Но это только упражнение и транзакции мы пока не проходили.
+// Поэтому, для упрощения, пока вешаем над классом репозитория
+@Transactional
+@Repository
+public class OtusStudentRepositoryJpa implements OtusStudentRepository {
+
+    @PersistenceContext
+    private EntityManager em;
+
+    @Override
+    public OtusStudent save(OtusStudent student) {
+        if (student.getId() <= 0) {
+            em.persist(student);
+            return student;
+        } else {
+            return em.merge(student);
+        }
+    }
+
+    @Override
+    public Optional<OtusStudent> findById(long id) {
+        return Optional.ofNullable(em.find(OtusStudent.class, id));
+    }
+
+    @Override
+    public List<OtusStudent> findAll() {
+        return em.createQuery("select s from OtusStudent s", OtusStudent.class)
+                .getResultList();
+    }
+
+    @Override
+    public List<OtusStudent> findByName(String name) {
+        TypedQuery<OtusStudent> query = em.createQuery("select s " +
+                        "from OtusStudent s " +
+                        "where s.name = :name",
+                OtusStudent.class);
+        query.setParameter("name", name);
+        return query.getResultList();
+    }
+
+    @Override
+    public void updateNameById(long id, String name) {
+        Query query = em.createQuery("update OtusStudent s " +
+                "set s.name = :name " +
+                "where s.id = :id");
+        query.setParameter("name", name);
+        query.setParameter("id", id);
+        query.executeUpdate();
+    }
+
+    @Override
+    public void deleteById(long id) {
+        Query query = em.createQuery("delete " +
+                        "from OtusStudent s " +
+                        "where s.id = :id");
+        query.setParameter("id", id);
+        query.executeUpdate();
+    }
+
+}
@@ -0,0 +1,15 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:testdb
+    initialization-mode: always
+
+  jpa:
+    generate-ddl: false
+    hibernate:
+      ddl-auto: none
+
+    show-sql: true
+
+logging:
+  level:
+    ROOT: ERROR
@@ -0,0 +1,31 @@
+create table avatars(
+    id bigserial,
+    photo_url varchar(8000),
+    primary key (id)
+);
+
+create table courses(
+    id bigserial,
+    name varchar(255),
+    primary key (id)
+);
+
+create table otus_students(
+    id bigserial,
+    name varchar(255),
+    avatar_id bigint references avatars (id),
+    primary key (id)
+);
+
+create table emails(
+    id bigserial,
+    student_id bigint references otus_students(id) on delete cascade,
+    email varchar(255),
+    primary key (id)
+);
+
+create table student_courses(
+    student_id bigint references otus_students(id) on delete cascade,
+    course_id bigint references courses(id),
+    primary key (student_id, course_id)
+);
@@ -0,0 +1,126 @@
+package ru.otus.example.ormdemo.repositories;
+
+import lombok.val;
+import org.hibernate.SessionFactory;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
+import org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManager;
+import org.springframework.context.annotation.Import;
+import ru.otus.example.ormdemo.models.OtusStudent;
+import ru.otus.example.ormdemo.models.Avatar;
+import ru.otus.example.ormdemo.models.Course;
+import ru.otus.example.ormdemo.models.EMail;
+
+import java.util.Collections;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@DisplayName("Репозиторий на основе Jpa для работы со студентами ")
+@DataJpaTest
+@Import(OtusStudentRepositoryJpa.class)
+class OtusStudentRepositoryJpaTest {
+
+    private static final int EXPECTED_NUMBER_OF_STUDENTS = 10;
+    private static final long FIRST_STUDENT_ID = 1L;
+    private static final String FIRST_STUDENT_NAME = "student_01";
+
+    private static final int EXPECTED_QUERIES_COUNT = 31;
+
+    private static final String STUDENT_AVATAR_URL = "где-то там";
+    private static final String STUDENT_EMAIL = "any@mail.com";
+    private static final String COURSE_NAME = "Spring";
+    private static final String STUDENT_NAME = "Вася";
+
+    @Autowired
+    private OtusStudentRepositoryJpa repositoryJpa;
+
+    @Autowired
+    private TestEntityManager em;
+
+    @DisplayName(" должен загружать информацию о нужном студенте по его id")
+    @Test
+    void shouldFindExpectedStudentById() {
+        val optionalActualStudent = repositoryJpa.findById(FIRST_STUDENT_ID);
+        val expectedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        assertThat(optionalActualStudent).isPresent().get()
+                .usingRecursiveComparison().isEqualTo(expectedStudent);
+    }
+
+    @DisplayName("должен загружать список всех студентов с полной информацией о них")
+    @Test
+    void shouldReturnCorrectStudentsListWithAllInfo() {
+        SessionFactory sessionFactory = em.getEntityManager().getEntityManagerFactory()
+                .unwrap(SessionFactory.class);
+        sessionFactory.getStatistics().setStatisticsEnabled(true);
+
+
+        System.out.println("\n\n\n\n----------------------------------------------------------------------------------------------------------");
+        val students = repositoryJpa.findAll();
+        assertThat(students).isNotNull().hasSize(EXPECTED_NUMBER_OF_STUDENTS)
+                .allMatch(s -> !s.getName().equals(""))
+                .allMatch(s -> s.getCourses() != null && s.getCourses().size() > 0)
+                .allMatch(s -> s.getAvatar() != null)
+                .allMatch(s -> s.getEmails() != null && s.getEmails().size() > 0);
+        System.out.println("----------------------------------------------------------------------------------------------------------\n\n\n\n");
+        assertThat(sessionFactory.getStatistics().getPrepareStatementCount()).isEqualTo(EXPECTED_QUERIES_COUNT);
+    }
+
+    @DisplayName(" должен корректно сохранять всю информацию о студенте")
+    @Test
+    void shouldSaveAllStudentInfo() {
+        val avatar = new Avatar(0, STUDENT_AVATAR_URL);
+        val email = new EMail(0, STUDENT_EMAIL);
+        val emails = Collections.singletonList(email);
+
+        val course = new Course(0, COURSE_NAME);
+        val courses = Collections.singletonList(course);
+
+
+        val vasya = new OtusStudent(0, STUDENT_NAME, avatar, emails, courses);
+        repositoryJpa.save(vasya);
+        assertThat(vasya.getId()).isGreaterThan(0);
+
+        val actualStudent = em.find(OtusStudent.class, vasya.getId());
+        assertThat(actualStudent).isNotNull().matches(s -> !s.getName().equals(""))
+                .matches(s -> s.getCourses() != null && s.getCourses().size() > 0 && s.getCourses().get(0).getId() > 0)
+                .matches(s -> s.getAvatar() != null)
+                .matches(s -> s.getEmails() != null && s.getEmails().size() > 0);
+    }
+
+    @DisplayName(" должен загружать информацию о нужном студенте по его имени")
+    @Test
+    void shouldFindExpectedStudentByName() {
+        val firstStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        List<OtusStudent> students = repositoryJpa.findByName(FIRST_STUDENT_NAME);
+        assertThat(students).containsOnlyOnce(firstStudent);
+    }
+
+    @DisplayName(" должен изменять имя заданного студента по его id")
+    @Test
+    void shouldUpdateStudentNameById() {
+        val firstStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        String oldName = firstStudent.getName();
+        em.detach(firstStudent);
+
+        repositoryJpa.updateNameById(FIRST_STUDENT_ID, STUDENT_NAME);
+        val updatedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+
+        assertThat(updatedStudent.getName()).isNotEqualTo(oldName).isEqualTo(STUDENT_NAME);
+    }
+
+    @DisplayName(" должен удалять заданного студента по его id")
+    @Test
+    void shouldDeleteStudentNameById() {
+        val firstStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        assertThat(firstStudent).isNotNull();
+        em.detach(firstStudent);
+
+        repositoryJpa.deleteById(FIRST_STUDENT_ID);
+        val deletedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+
+        assertThat(deletedStudent).isNull();
+    }
+}
@@ -0,0 +1,17 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:testdb
+    initialization-mode: always
+
+  jpa:
+    generate-ddl: false
+    #generate-ddl: true
+    hibernate:
+      ddl-auto: none
+      #ddl-auto: create-drop
+
+    #show-sql: true
+
+logging:
+  level:
+    ROOT: ERROR
@@ -0,0 +1,29 @@
+insert into avatars(photo_url)
+values ('photoUrl_01'), ('photoUrl_02'), ('photoUrl_03'), ('photoUrl_04'), ('photoUrl_05'),
+       ('photoUrl_06'), ('photoUrl_07'), ('photoUrl_08'), ('photoUrl_09'), ('photoUrl_10');
+
+insert into courses(name)
+values ('course_name_01'), ('course_name_02'), ('course_name_03'), ('course_name_04'), ('course_name_05'),
+       ('course_name_06'), ('course_name_07'), ('course_name_08'), ('course_name_09'), ('course_name_10'), ('not_used_11');
+
+insert into otus_students(name, avatar_id)
+values ('student_01', 1), ('student_02', 2), ('student_03', 3), ('student_04', 4), ('student_05', 5),
+       ('student_06', 6), ('student_07', 7), ('student_08', 8), ('student_09', 9), ('student_10', 10);
+
+
+insert into emails(email, student_id)
+values ('email_01', 1), ('email_02', 1), ('email_03', 2), ('email_04', 2), ('email_05', 3), ('email_06', 4),
+       ('email_07', 5), ('email_08', 6), ('email_09', 7), ('email_10', 8), ('email_11', 9), ('email_12', 10);
+
+
+insert into student_courses(student_id, course_id)
+values (1, 1),   (1, 2),   (1, 3),
+       (2, 2),   (2, 4),   (2, 5),
+       (3, 3),   (3, 6),   (3, 7),
+       (4, 4),   (4, 8),   (4, 9),
+       (5, 5),   (5, 10),  (5, 1),
+       (6, 6),   (6, 2),   (6, 3),
+       (7, 7),   (7, 4),   (7, 5),
+       (8, 8),   (8, 6),   (8, 7),
+       (9, 9),   (9, 8),   (9, 10),
+       (10, 10), (10, 1),  (10, 2);
@@ -0,0 +1,4 @@
+.idea/
+*.iml
+
+target/
@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>ru.otus</groupId>
+    <artifactId>jpql-solution-04</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.5.4</version>
+    </parent>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <scope>runtime</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <optional>true</optional>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+</project>
@@ -0,0 +1,13 @@
+package ru.otus.example.ormdemo;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class OrmDemoApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(OrmDemoApplication.class, args);
+	}
+
+}
@@ -0,0 +1,21 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "avatars")
+public class Avatar {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "photo_url", nullable = false, unique = true)
+    private String photoUrl;
+}
@@ -0,0 +1,21 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "courses")
+public class Course {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "name", nullable = false, unique = true)
+    private String name;
+}
@@ -0,0 +1,22 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "emails")
+public class EMail {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "email", nullable = false, unique = true)
+    private String email;
+}
@@ -0,0 +1,42 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.*;
+
+import javax.persistence.*;
+import java.util.List;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity // Указывает, что данный класс является сущностью
+@Table(name = "otus_students") // Задает имя таблицы, на которую будет отображаться сущность
+// Позволяет указать какие связи родительской сущности загружать в одном с ней запросе
+@NamedEntityGraph(name = "otus-student-avatars-entity-graph",
+        attributeNodes = {@NamedAttributeNode("avatar")})
+public class OtusStudent {
+    @Id // Позволяет указать какое поле является идентификатором
+    @GeneratedValue(strategy = GenerationType.IDENTITY) // Стратегия генерации идентификаторов
+    private long id;
+
+    // Задает имя и некоторые свойства поля таблицы, на которое будет отображаться поле сущности
+    @Column(name = "name", nullable = false, unique = true)
+    private String name;
+
+    // Указывает на связь между таблицами "один к одному"
+    @OneToOne(targetEntity = Avatar.class, cascade = CascadeType.ALL)
+    // Задает поле, по которому происходит объединение с таблицей для хранения связанной сущности
+    @JoinColumn(name = "avatar_id")
+    private Avatar avatar;
+
+    // Указывает на связь между таблицами "один ко многим"
+    @OneToMany(targetEntity = EMail.class, cascade = CascadeType.ALL, fetch = FetchType.EAGER)
+    @JoinColumn(name = "student_id")
+    private List<EMail> emails;
+
+    // Указывает на связь между таблицами "многие ко многим"
+    @ManyToMany(targetEntity = Course.class, fetch = FetchType.LAZY, cascade = CascadeType.ALL)
+    // Задает таблицу связей между таблицами для хранения родительской и связанной сущностью
+    @JoinTable(name = "student_courses", joinColumns = @JoinColumn(name = "student_id"),
+            inverseJoinColumns = @JoinColumn(name = "course_id"))
+    private List<Course> courses;
+}
@@ -0,0 +1,18 @@
+package ru.otus.example.ormdemo.repositories;
+
+
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface OtusStudentRepository {
+    OtusStudent save(OtusStudent student);
+    Optional<OtusStudent> findById(long id);
+
+    List<OtusStudent> findAll();
+    List<OtusStudent> findByName(String name);
+
+    void updateNameById(long id, String name);
+    void deleteById(long id);
+}
@@ -0,0 +1,79 @@
+package ru.otus.example.ormdemo.repositories;
+
+import org.springframework.stereotype.Repository;
+import org.springframework.transaction.annotation.Transactional;
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import javax.persistence.*;
+import java.util.List;
+import java.util.Optional;
+
+// @Transactional должна стоять на методе сервиса.
+// Причем, если метод не подразумевает изменения данных в БД то категорически желательно
+// выставить у аннотации параметр readOnly в true.
+// Но это только упражнение и транзакции мы пока не проходили.
+// Поэтому, для упрощения, пока вешаем над классом репозитория
+@Transactional
+@Repository
+public class OtusStudentRepositoryJpa implements OtusStudentRepository {
+
+    @PersistenceContext
+    private final EntityManager em;
+
+    public OtusStudentRepositoryJpa(EntityManager em) {
+        this.em = em;
+    }
+
+    @Override
+    public OtusStudent save(OtusStudent student) {
+        if (student.getId() <= 0) {
+            em.persist(student);
+            return student;
+        } else {
+            return em.merge(student);
+        }
+    }
+
+    @Override
+    public Optional<OtusStudent> findById(long id) {
+        return Optional.ofNullable(em.find(OtusStudent.class, id));
+    }
+
+    @Override
+    public List<OtusStudent> findAll() {
+        EntityGraph<?> entityGraph = em.getEntityGraph("otus-student-avatars-entity-graph");
+        TypedQuery<OtusStudent> query = em.createQuery("select s from OtusStudent s", OtusStudent.class);
+        query.setHint("javax.persistence.fetchgraph", entityGraph);
+        return query.getResultList();
+    }
+
+    @Override
+    public List<OtusStudent> findByName(String name) {
+        TypedQuery<OtusStudent> query = em.createQuery("select s " +
+                        "from OtusStudent s " +
+                        "where s.name = :name",
+                OtusStudent.class);
+        query.setParameter("name", name);
+        return query.getResultList();
+    }
+
+    @Override
+    public void updateNameById(long id, String name) {
+        Query query = em.createQuery("update OtusStudent s " +
+                "set s.name = :name " +
+                "where s.id = :id");
+        query.setParameter("name", name);
+        query.setParameter("id", id);
+        query.executeUpdate();
+    }
+
+    @Override
+    public void deleteById(long id) {
+        Query query = em.createQuery("delete " +
+                        "from OtusStudent s " +
+                        "where s.id = :id");
+        query.setParameter("id", id);
+        query.executeUpdate();
+    }
+
+}
@@ -0,0 +1,15 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:testdb
+    initialization-mode: always
+
+  jpa:
+    generate-ddl: false
+    hibernate:
+      ddl-auto: none
+
+    show-sql: true
+
+logging:
+  level:
+    ROOT: ERROR
@@ -0,0 +1,31 @@
+create table avatars(
+    id bigserial,
+    photo_url varchar(8000),
+    primary key (id)
+);
+
+create table courses(
+    id bigserial,
+    name varchar(255),
+    primary key (id)
+);
+
+create table otus_students(
+    id bigserial,
+    name varchar(255),
+    avatar_id bigint references avatars (id),
+    primary key (id)
+);
+
+create table emails(
+    id bigserial,
+    student_id bigint references otus_students(id) on delete cascade,
+    email varchar(255),
+    primary key (id)
+);
+
+create table student_courses(
+    student_id bigint references otus_students(id) on delete cascade,
+    course_id bigint references courses(id),
+    primary key (student_id, course_id)
+);
@@ -0,0 +1,58 @@
+package ru.otus.example.ormdemo.repositories;
+
+import lombok.val;
+import org.hibernate.SessionFactory;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
+import org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManager;
+import org.springframework.context.annotation.Import;
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@DisplayName("Репозиторий на основе Jpa для работы со студентами ")
+@DataJpaTest
+@Import(OtusStudentRepositoryJpa.class)
+class OtusStudentRepositoryJpaTest {
+
+    private static final int EXPECTED_NUMBER_OF_STUDENTS = 10;
+    private static final long FIRST_STUDENT_ID = 1L;
+
+    private static final int EXPECTED_QUERIES_COUNT = 21;
+
+    @Autowired
+    private OtusStudentRepositoryJpa repositoryJpa;
+
+    @Autowired
+    private TestEntityManager em;
+
+    @DisplayName(" должен загружать информацию о нужном студенте по его id")
+    @Test
+    void shouldFindExpectedStudentById() {
+        val optionalActualStudent = repositoryJpa.findById(FIRST_STUDENT_ID);
+        val expectedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        assertThat(optionalActualStudent).isPresent().get()
+                .usingRecursiveComparison().isEqualTo(expectedStudent);
+    }
+
+    @DisplayName("должен загружать список всех студентов с полной информацией о них")
+    @Test
+    void shouldReturnCorrectStudentsListWithAllInfo() {
+        SessionFactory sessionFactory = em.getEntityManager().getEntityManagerFactory()
+                .unwrap(SessionFactory.class);
+        sessionFactory.getStatistics().setStatisticsEnabled(true);
+
+
+        System.out.println("\n\n\n\n----------------------------------------------------------------------------------------------------------");
+        val students = repositoryJpa.findAll();
+        assertThat(students).isNotNull().hasSize(EXPECTED_NUMBER_OF_STUDENTS)
+                .allMatch(s -> !s.getName().equals(""))
+                .allMatch(s -> s.getCourses() != null && s.getCourses().size() > 0)
+                .allMatch(s -> s.getAvatar() != null)
+                .allMatch(s -> s.getEmails() != null && s.getEmails().size() > 0);
+        System.out.println("----------------------------------------------------------------------------------------------------------\n\n\n\n");
+        assertThat(sessionFactory.getStatistics().getPrepareStatementCount()).isEqualTo(EXPECTED_QUERIES_COUNT);
+    }
+}
@@ -0,0 +1,17 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:testdb
+    initialization-mode: always
+
+  jpa:
+    generate-ddl: false
+    #generate-ddl: true
+    hibernate:
+      ddl-auto: none
+      #ddl-auto: create-drop
+
+    #show-sql: true
+
+logging:
+  level:
+    ROOT: ERROR
@@ -0,0 +1,29 @@
+insert into avatars(photo_url)
+values ('photoUrl_01'), ('photoUrl_02'), ('photoUrl_03'), ('photoUrl_04'), ('photoUrl_05'),
+       ('photoUrl_06'), ('photoUrl_07'), ('photoUrl_08'), ('photoUrl_09'), ('photoUrl_10');
+
+insert into courses(name)
+values ('course_name_01'), ('course_name_02'), ('course_name_03'), ('course_name_04'), ('course_name_05'),
+       ('course_name_06'), ('course_name_07'), ('course_name_08'), ('course_name_09'), ('course_name_10'), ('not_used_11');
+
+insert into otus_students(name, avatar_id)
+values ('student_01', 1), ('student_02', 2), ('student_03', 3), ('student_04', 4), ('student_05', 5),
+       ('student_06', 6), ('student_07', 7), ('student_08', 8), ('student_09', 9), ('student_10', 10);
+
+
+insert into emails(email, student_id)
+values ('email_01', 1), ('email_02', 1), ('email_03', 2), ('email_04', 2), ('email_05', 3), ('email_06', 4),
+       ('email_07', 5), ('email_08', 6), ('email_09', 7), ('email_10', 8), ('email_11', 9), ('email_12', 10);
+
+
+insert into student_courses(student_id, course_id)
+values (1, 1),   (1, 2),   (1, 3),
+       (2, 2),   (2, 4),   (2, 5),
+       (3, 3),   (3, 6),   (3, 7),
+       (4, 4),   (4, 8),   (4, 9),
+       (5, 5),   (5, 10),  (5, 1),
+       (6, 6),   (6, 2),   (6, 3),
+       (7, 7),   (7, 4),   (7, 5),
+       (8, 8),   (8, 6),   (8, 7),
+       (9, 9),   (9, 8),   (9, 10),
+       (10, 10), (10, 1),  (10, 2);
@@ -0,0 +1,4 @@
+.idea/
+*.iml
+
+target/
@@ -0,0 +1,56 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>ru.otus</groupId>
+    <artifactId>jpql-solution-05</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.5.4</version>
+    </parent>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <scope>runtime</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <optional>true</optional>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+</project>
@@ -0,0 +1,13 @@
+package ru.otus.example.ormdemo;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class OrmDemoApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(OrmDemoApplication.class, args);
+	}
+
+}
@@ -0,0 +1,21 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "avatars")
+public class Avatar {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "photo_url", nullable = false, unique = true)
+    private String photoUrl;
+}
@@ -0,0 +1,21 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "courses")
+public class Course {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "name", nullable = false, unique = true)
+    private String name;
+}
@@ -0,0 +1,22 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "emails")
+public class EMail {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "email", nullable = false, unique = true)
+    private String email;
+}
@@ -0,0 +1,42 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.*;
+
+import javax.persistence.*;
+import java.util.List;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity // Указывает, что данный класс является сущностью
+@Table(name = "otus_students") // Задает имя таблицы, на которую будет отображаться сущность
+// Позволяет указать какие связи родительской сущности загружать в одном с ней запросе
+@NamedEntityGraph(name = "otus-student-avatars-entity-graph",
+        attributeNodes = {@NamedAttributeNode("avatar")})
+public class OtusStudent {
+    @Id // Позволяет указать какое поле является идентификатором
+    @GeneratedValue(strategy = GenerationType.IDENTITY) // Стратегия генерации идентификаторов
+    private long id;
+
+    // Задает имя и некоторые свойства поля таблицы, на которое будет отображаться поле сущности
+    @Column(name = "name", nullable = false, unique = true)
+    private String name;
+
+    // Указывает на связь между таблицами "один к одному"
+    @OneToOne(targetEntity = Avatar.class, cascade = CascadeType.ALL)
+    // Задает поле, по которому происходит объединение с таблицей для хранения связанной сущности
+    @JoinColumn(name = "avatar_id")
+    private Avatar avatar;
+
+    // Указывает на связь между таблицами "один ко многим"
+    @OneToMany(targetEntity = EMail.class, cascade = CascadeType.ALL, fetch = FetchType.EAGER)
+    @JoinColumn(name = "student_id")
+    private List<EMail> emails;
+
+    // Указывает на связь между таблицами "многие ко многим"
+    @ManyToMany(targetEntity = Course.class, fetch = FetchType.LAZY, cascade = CascadeType.ALL)
+    // Задает таблицу связей между таблицами для хранения родительской и связанной сущностью
+    @JoinTable(name = "student_courses", joinColumns = @JoinColumn(name = "student_id"),
+            inverseJoinColumns = @JoinColumn(name = "course_id"))
+    private List<Course> courses;
+}
@@ -0,0 +1,18 @@
+package ru.otus.example.ormdemo.repositories;
+
+
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface OtusStudentRepository {
+    OtusStudent save(OtusStudent student);
+    Optional<OtusStudent> findById(long id);
+
+    List<OtusStudent> findAll();
+    List<OtusStudent> findByName(String name);
+
+    void updateNameById(long id, String name);
+    void deleteById(long id);
+}
@@ -0,0 +1,79 @@
+package ru.otus.example.ormdemo.repositories;
+
+import org.springframework.stereotype.Repository;
+import org.springframework.transaction.annotation.Transactional;
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import javax.persistence.*;
+import java.util.List;
+import java.util.Optional;
+
+// @Transactional должна стоять на методе сервиса.
+// Причем, если метод не подразумевает изменения данных в БД то категорически желательно
+// выставить у аннотации параметр readOnly в true.
+// Но это только упражнение и транзакции мы пока не проходили.
+// Поэтому, для упрощения, пока вешаем над классом репозитория
+@Transactional
+@Repository
+public class OtusStudentRepositoryJpa implements OtusStudentRepository {
+
+    @PersistenceContext
+    private final EntityManager em;
+
+    public OtusStudentRepositoryJpa(EntityManager em) {
+        this.em = em;
+    }
+
+    @Override
+    public OtusStudent save(OtusStudent student) {
+        if (student.getId() <= 0) {
+            em.persist(student);
+            return student;
+        } else {
+            return em.merge(student);
+        }
+    }
+
+    @Override
+    public Optional<OtusStudent> findById(long id) {
+        return Optional.ofNullable(em.find(OtusStudent.class, id));
+    }
+
+    @Override
+    public List<OtusStudent> findAll() {
+        EntityGraph<?> entityGraph = em.getEntityGraph("otus-student-avatars-entity-graph");
+        TypedQuery<OtusStudent> query = em.createQuery("select s from OtusStudent s join fetch s.emails", OtusStudent.class);
+        query.setHint("javax.persistence.fetchgraph", entityGraph);
+        return query.getResultList();
+    }
+
+    @Override
+    public List<OtusStudent> findByName(String name) {
+        TypedQuery<OtusStudent> query = em.createQuery("select s " +
+                        "from OtusStudent s " +
+                        "where s.name = :name",
+                OtusStudent.class);
+        query.setParameter("name", name);
+        return query.getResultList();
+    }
+
+    @Override
+    public void updateNameById(long id, String name) {
+        Query query = em.createQuery("update OtusStudent s " +
+                "set s.name = :name " +
+                "where s.id = :id");
+        query.setParameter("name", name);
+        query.setParameter("id", id);
+        query.executeUpdate();
+    }
+
+    @Override
+    public void deleteById(long id) {
+        Query query = em.createQuery("delete " +
+                        "from OtusStudent s " +
+                        "where s.id = :id");
+        query.setParameter("id", id);
+        query.executeUpdate();
+    }
+
+}
@@ -0,0 +1,15 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:testdb
+    initialization-mode: always
+
+  jpa:
+    generate-ddl: false
+    hibernate:
+      ddl-auto: none
+
+    show-sql: true
+
+logging:
+  level:
+    ROOT: ERROR
@@ -0,0 +1,31 @@
+create table avatars(
+    id bigserial,
+    photo_url varchar(8000),
+    primary key (id)
+);
+
+create table courses(
+    id bigserial,
+    name varchar(255),
+    primary key (id)
+);
+
+create table otus_students(
+    id bigserial,
+    name varchar(255),
+    avatar_id bigint references avatars (id),
+    primary key (id)
+);
+
+create table emails(
+    id bigserial,
+    student_id bigint references otus_students(id) on delete cascade,
+    email varchar(255),
+    primary key (id)
+);
+
+create table student_courses(
+    student_id bigint references otus_students(id) on delete cascade,
+    course_id bigint references courses(id),
+    primary key (student_id, course_id)
+);
@@ -0,0 +1,58 @@
+package ru.otus.example.ormdemo.repositories;
+
+import lombok.val;
+import org.hibernate.SessionFactory;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
+import org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManager;
+import org.springframework.context.annotation.Import;
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@DisplayName("Репозиторий на основе Jpa для работы со студентами ")
+@DataJpaTest
+@Import(OtusStudentRepositoryJpa.class)
+class OtusStudentRepositoryJpaTest {
+
+    private static final int EXPECTED_NUMBER_OF_STUDENTS = 10;
+    private static final long FIRST_STUDENT_ID = 1L;
+
+    private static final int EXPECTED_QUERIES_COUNT = 11;
+
+    @Autowired
+    private OtusStudentRepositoryJpa repositoryJpa;
+
+    @Autowired
+    private TestEntityManager em;
+
+    @DisplayName(" должен загружать информацию о нужном студенте по его id")
+    @Test
+    void shouldFindExpectedStudentById() {
+        val optionalActualStudent = repositoryJpa.findById(FIRST_STUDENT_ID);
+        val expectedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        assertThat(optionalActualStudent).isPresent().get()
+                .usingRecursiveComparison().isEqualTo(expectedStudent);
+    }
+
+    @DisplayName("должен загружать список всех студентов с полной информацией о них")
+    @Test
+    void shouldReturnCorrectStudentsListWithAllInfo() {
+        SessionFactory sessionFactory = em.getEntityManager().getEntityManagerFactory()
+                .unwrap(SessionFactory.class);
+        sessionFactory.getStatistics().setStatisticsEnabled(true);
+
+
+        System.out.println("\n\n\n\n----------------------------------------------------------------------------------------------------------");
+        val students = repositoryJpa.findAll();
+        assertThat(students).isNotNull().hasSize(EXPECTED_NUMBER_OF_STUDENTS)
+                .allMatch(s -> !s.getName().equals(""))
+                .allMatch(s -> s.getCourses() != null && s.getCourses().size() > 0)
+                .allMatch(s -> s.getAvatar() != null)
+                .allMatch(s -> s.getEmails() != null && s.getEmails().size() > 0);
+        System.out.println("----------------------------------------------------------------------------------------------------------\n\n\n\n");
+        assertThat(sessionFactory.getStatistics().getPrepareStatementCount()).isEqualTo(EXPECTED_QUERIES_COUNT);
+    }
+}
@@ -0,0 +1,17 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:testdb
+    initialization-mode: always
+
+  jpa:
+    generate-ddl: false
+    #generate-ddl: true
+    hibernate:
+      ddl-auto: none
+      #ddl-auto: create-drop
+
+    #show-sql: true
+
+logging:
+  level:
+    ROOT: ERROR
@@ -0,0 +1,29 @@
+insert into avatars(photo_url)
+values ('photoUrl_01'), ('photoUrl_02'), ('photoUrl_03'), ('photoUrl_04'), ('photoUrl_05'),
+       ('photoUrl_06'), ('photoUrl_07'), ('photoUrl_08'), ('photoUrl_09'), ('photoUrl_10');
+
+insert into courses(name)
+values ('course_name_01'), ('course_name_02'), ('course_name_03'), ('course_name_04'), ('course_name_05'),
+       ('course_name_06'), ('course_name_07'), ('course_name_08'), ('course_name_09'), ('course_name_10'), ('not_used_11');
+
+insert into otus_students(name, avatar_id)
+values ('student_01', 1), ('student_02', 2), ('student_03', 3), ('student_04', 4), ('student_05', 5),
+       ('student_06', 6), ('student_07', 7), ('student_08', 8), ('student_09', 9), ('student_10', 10);
+
+
+insert into emails(email, student_id)
+values ('email_01', 1), ('email_02', 1), ('email_03', 2), ('email_04', 2), ('email_05', 3), ('email_06', 4),
+       ('email_07', 5), ('email_08', 6), ('email_09', 7), ('email_10', 8), ('email_11', 9), ('email_12', 10);
+
+
+insert into student_courses(student_id, course_id)
+values (1, 1),   (1, 2),   (1, 3),
+       (2, 2),   (2, 4),   (2, 5),
+       (3, 3),   (3, 6),   (3, 7),
+       (4, 4),   (4, 8),   (4, 9),
+       (5, 5),   (5, 10),  (5, 1),
+       (6, 6),   (6, 2),   (6, 3),
+       (7, 7),   (7, 4),   (7, 5),
+       (8, 8),   (8, 6),   (8, 7),
+       (9, 9),   (9, 8),   (9, 10),
+       (10, 10), (10, 1),  (10, 2);
@@ -0,0 +1,4 @@
+.idea/
+*.iml
+
+target/
@@ -0,0 +1,56 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>ru.otus</groupId>
+    <artifactId>jpql-solution-06</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.5.4</version>
+    </parent>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <scope>runtime</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <optional>true</optional>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+</project>
@@ -0,0 +1,13 @@
+package ru.otus.example.ormdemo;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class OrmDemoApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(OrmDemoApplication.class, args);
+	}
+
+}
@@ -0,0 +1,21 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "avatars")
+public class Avatar {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "photo_url", nullable = false, unique = true)
+    private String photoUrl;
+}
@@ -0,0 +1,21 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "courses")
+public class Course {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "name", nullable = false, unique = true)
+    private String name;
+}
@@ -0,0 +1,22 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity
+@Table(name = "emails")
+public class EMail {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+
+    @Column(name = "email", nullable = false, unique = true)
+    private String email;
+}
@@ -0,0 +1,48 @@
+package ru.otus.example.ormdemo.models;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+import org.hibernate.annotations.Fetch;
+import org.hibernate.annotations.FetchMode;
+
+import javax.persistence.*;
+import java.util.List;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Entity // Указывает, что данный класс является сущностью
+@Table(name = "otus_students") // Задает имя таблицы, на которую будет отображаться сущность
+// Позволяет указать какие связи родительской сущности загружать в одном с ней запросе
+@NamedEntityGraph(name = "otus-student-avatars-entity-graph",
+        attributeNodes = {@NamedAttributeNode("avatar")})
+public class OtusStudent {
+    @Id // Позволяет указать какое поле является идентификатором
+    @GeneratedValue(strategy = GenerationType.IDENTITY) // Стратегия генерации идентификаторов
+    private long id;
+
+    // Задает имя и некоторые свойства поля таблицы, на которое будет отображаться поле сущности
+    @Column(name = "name", nullable = false, unique = true)
+    private String name;
+
+    // Указывает на связь между таблицами "один к одному"
+    @OneToOne(targetEntity = Avatar.class, cascade = CascadeType.ALL)
+    // Задает поле, по которому происходит объединение с таблицей для хранения связанной сущности
+    @JoinColumn(name = "avatar_id")
+    private Avatar avatar;
+
+    // Указывает на связь между таблицами "один ко многим"
+    @OneToMany(targetEntity = EMail.class, cascade = CascadeType.ALL, fetch = FetchType.EAGER)
+    @JoinColumn(name = "student_id")
+    private List<EMail> emails;
+
+    // Все данные талицы будут загружены в память отдельным запросом и соединены с родительской сущностью
+    @Fetch(FetchMode.SUBSELECT)
+    // Указывает на связь между таблицами "многие ко многим"
+    @ManyToMany(targetEntity = Course.class, fetch = FetchType.LAZY, cascade = CascadeType.ALL)
+    // Задает таблицу связей между таблицами для хранения родительской и связанной сущностью
+    @JoinTable(name = "student_courses", joinColumns = @JoinColumn(name = "student_id"),
+            inverseJoinColumns = @JoinColumn(name = "course_id"))
+    private List<Course> courses;
+}
@@ -0,0 +1,18 @@
+package ru.otus.example.ormdemo.repositories;
+
+
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface OtusStudentRepository {
+    OtusStudent save(OtusStudent student);
+    Optional<OtusStudent> findById(long id);
+
+    List<OtusStudent> findAll();
+    List<OtusStudent> findByName(String name);
+
+    void updateNameById(long id, String name);
+    void deleteById(long id);
+}
@@ -0,0 +1,79 @@
+package ru.otus.example.ormdemo.repositories;
+
+import org.springframework.stereotype.Repository;
+import org.springframework.transaction.annotation.Transactional;
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import javax.persistence.*;
+import java.util.List;
+import java.util.Optional;
+
+// @Transactional должна стоять на методе сервиса.
+// Причем, если метод не подразумевает изменения данных в БД то категорически желательно
+// выставить у аннотации параметр readOnly в true.
+// Но это только упражнение и транзакции мы пока не проходили.
+// Поэтому, для упрощения, пока вешаем над классом репозитория
+@Transactional
+@Repository
+public class OtusStudentRepositoryJpa implements OtusStudentRepository {
+
+    @PersistenceContext
+    private final EntityManager em;
+
+    public OtusStudentRepositoryJpa(EntityManager em) {
+        this.em = em;
+    }
+
+    @Override
+    public OtusStudent save(OtusStudent student) {
+        if (student.getId() <= 0) {
+            em.persist(student);
+            return student;
+        } else {
+            return em.merge(student);
+        }
+    }
+
+    @Override
+    public Optional<OtusStudent> findById(long id) {
+        return Optional.ofNullable(em.find(OtusStudent.class, id));
+    }
+
+    @Override
+    public List<OtusStudent> findAll() {
+        EntityGraph<?> entityGraph = em.getEntityGraph("otus-student-avatars-entity-graph");
+        TypedQuery<OtusStudent> query = em.createQuery("select s from OtusStudent s join fetch s.emails", OtusStudent.class);
+        query.setHint("javax.persistence.fetchgraph", entityGraph);
+        return query.getResultList();
+    }
+
+    @Override
+    public List<OtusStudent> findByName(String name) {
+        TypedQuery<OtusStudent> query = em.createQuery("select s " +
+                        "from OtusStudent s " +
+                        "where s.name = :name",
+                OtusStudent.class);
+        query.setParameter("name", name);
+        return query.getResultList();
+    }
+
+    @Override
+    public void updateNameById(long id, String name) {
+        Query query = em.createQuery("update OtusStudent s " +
+                "set s.name = :name " +
+                "where s.id = :id");
+        query.setParameter("name", name);
+        query.setParameter("id", id);
+        query.executeUpdate();
+    }
+
+    @Override
+    public void deleteById(long id) {
+        Query query = em.createQuery("delete " +
+                        "from OtusStudent s " +
+                        "where s.id = :id");
+        query.setParameter("id", id);
+        query.executeUpdate();
+    }
+
+}
@@ -0,0 +1,15 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:testdb
+    initialization-mode: always
+
+  jpa:
+    generate-ddl: false
+    hibernate:
+      ddl-auto: none
+
+    show-sql: true
+
+logging:
+  level:
+    ROOT: ERROR
@@ -0,0 +1,31 @@
+create table avatars(
+    id bigserial,
+    photo_url varchar(8000),
+    primary key (id)
+);
+
+create table courses(
+    id bigserial,
+    name varchar(255),
+    primary key (id)
+);
+
+create table otus_students(
+    id bigserial,
+    name varchar(255),
+    avatar_id bigint references avatars (id),
+    primary key (id)
+);
+
+create table emails(
+    id bigserial,
+    student_id bigint references otus_students(id) on delete cascade,
+    email varchar(255),
+    primary key (id)
+);
+
+create table student_courses(
+    student_id bigint references otus_students(id) on delete cascade,
+    course_id bigint references courses(id),
+    primary key (student_id, course_id)
+);
@@ -0,0 +1,58 @@
+package ru.otus.example.ormdemo.repositories;
+
+import lombok.val;
+import org.hibernate.SessionFactory;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
+import org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManager;
+import org.springframework.context.annotation.Import;
+import ru.otus.example.ormdemo.models.OtusStudent;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@DisplayName("Репозиторий на основе Jpa для работы со студентами ")
+@DataJpaTest
+@Import(OtusStudentRepositoryJpa.class)
+class OtusStudentRepositoryJpaTest {
+
+    private static final int EXPECTED_NUMBER_OF_STUDENTS = 10;
+    private static final long FIRST_STUDENT_ID = 1L;
+
+    private static final int EXPECTED_QUERIES_COUNT = 2;
+
+    @Autowired
+    private OtusStudentRepositoryJpa repositoryJpa;
+
+    @Autowired
+    private TestEntityManager em;
+
+    @DisplayName(" должен загружать информацию о нужном студенте по его id")
+    @Test
+    void shouldFindExpectedStudentById() {
+        val optionalActualStudent = repositoryJpa.findById(FIRST_STUDENT_ID);
+        val expectedStudent = em.find(OtusStudent.class, FIRST_STUDENT_ID);
+        assertThat(optionalActualStudent).isPresent().get()
+                .usingRecursiveComparison().isEqualTo(expectedStudent);
+    }
+
+    @DisplayName("должен загружать список всех студентов с полной информацией о них")
+    @Test
+    void shouldReturnCorrectStudentsListWithAllInfo() {
+        SessionFactory sessionFactory = em.getEntityManager().getEntityManagerFactory()
+                .unwrap(SessionFactory.class);
+        sessionFactory.getStatistics().setStatisticsEnabled(true);
+
+
+        System.out.println("\n\n\n\n----------------------------------------------------------------------------------------------------------");
+        val students = repositoryJpa.findAll();
+        assertThat(students).isNotNull().hasSize(EXPECTED_NUMBER_OF_STUDENTS)
+                .allMatch(s -> !s.getName().equals(""))
+                .allMatch(s -> s.getCourses() != null && s.getCourses().size() > 0)
+                .allMatch(s -> s.getAvatar() != null)
+                .allMatch(s -> s.getEmails() != null && s.getEmails().size() > 0);
+        System.out.println("----------------------------------------------------------------------------------------------------------\n\n\n\n");
+        assertThat(sessionFactory.getStatistics().getPrepareStatementCount()).isEqualTo(EXPECTED_QUERIES_COUNT);
+    }
+}
@@ -0,0 +1,17 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:testdb
+    initialization-mode: always
+
+  jpa:
+    generate-ddl: false
+    #generate-ddl: true
+    hibernate:
+      ddl-auto: none
+      #ddl-auto: create-drop
+
+    #show-sql: true
+
+logging:
+  level:
+    ROOT: ERROR
@@ -0,0 +1,29 @@
+insert into avatars(photo_url)
+values ('photoUrl_01'), ('photoUrl_02'), ('photoUrl_03'), ('photoUrl_04'), ('photoUrl_05'),
+       ('photoUrl_06'), ('photoUrl_07'), ('photoUrl_08'), ('photoUrl_09'), ('photoUrl_10');
+
+insert into courses(name)
+values ('course_name_01'), ('course_name_02'), ('course_name_03'), ('course_name_04'), ('course_name_05'),
+       ('course_name_06'), ('course_name_07'), ('course_name_08'), ('course_name_09'), ('course_name_10'), ('not_used_11');
+
+insert into otus_students(name, avatar_id)
+values ('student_01', 1), ('student_02', 2), ('student_03', 3), ('student_04', 4), ('student_05', 5),
+       ('student_06', 6), ('student_07', 7), ('student_08', 8), ('student_09', 9), ('student_10', 10);
+
+
+insert into emails(email, student_id)
+values ('email_01', 1), ('email_02', 1), ('email_03', 2), ('email_04', 2), ('email_05', 3), ('email_06', 4),
+       ('email_07', 5), ('email_08', 6), ('email_09', 7), ('email_10', 8), ('email_11', 9), ('email_12', 10);
+
+
+insert into student_courses(student_id, course_id)
+values (1, 1),   (1, 2),   (1, 3),
+       (2, 2),   (2, 4),   (2, 5),
+       (3, 3),   (3, 6),   (3, 7),
+       (4, 4),   (4, 8),   (4, 9),
+       (5, 5),   (5, 10),  (5, 1),
+       (6, 6),   (6, 2),   (6, 3),
+       (7, 7),   (7, 4),   (7, 5),
+       (8, 8),   (8, 6),   (8, 7),
+       (9, 9),   (9, 8),   (9, 10),
+       (10, 10), (10, 1),  (10, 2);
@@ -0,0 +1,4 @@
+.idea/
+*.iml
+
+target/
@@ -0,0 +1,56 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>ru.otus</groupId>
+    <artifactId>jpql-solution-final</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.5.4</version>
+    </parent>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <scope>runtime</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <optional>true</optional>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+</project>
--- a/Show More
+++ b/Show More