Spring Data JPA kirish

Bu bo‘limda Spring Boot’da database bilan ishlashni boshlaymiz. Bu mavzu ichida @Entity, @Id, @GeneratedValue, JpaRepository, H2 in-memory database, spring.datasource configuration, @Column, @Table bor.

1. Spring Data JPA nima?

Spring Data JPA - database bilan ishlashni osonlashtiradigan Spring moduli.

Oddiy Java’da database bilan ishlash uchun ko‘p kod yoziladi:

Connection connection = DriverManager.getConnection(...);
PreparedStatement statement = connection.prepareStatement(...);
ResultSet resultSet = statement.executeQuery();

Spring Data JPA’da esa ko‘pincha bunday yozamiz:

userRepository.findAll();
userRepository.findById(1L);
userRepository.save(user);
userRepository.deleteById(1L);

Ya’ni:

Spring Data JPA database bilan CRUD qilishni juda osonlashtiradi.

2. JPA nima?

JPA - Java Persistence API.

Oddiy tushuncha:

JPA - Java objectlarni database table bilan bog‘lash standarti.

Masalan, Java’da User class bor:

public class User {
    private Long id;
    private String name;
    private String email;
}

Database’da esa users table bor:

CREATE TABLE users (
    id BIGINT PRIMARY KEY,
    name VARCHAR(255),
    email VARCHAR(255)
);

JPA shu Java class bilan database table o‘rtasida mapping qiladi.

3. ORM nima?

ORM - Object Relational Mapping.

Ya’ni:

Java object  ↔  Database table
Class        ↔  Table
Field        ↔  Column
Object       ↔  Row

Misol:

Spring Boot’da JPA uchun odatda Hibernate ishlatiladi.

4. Spring Data JPA nima qiladi?

Spring Data JPA quyidagi ishlarni osonlashtiradi:

Ma’lumot saqlash
Ma’lumot olish
Ma’lumot yangilash
Ma’lumot o‘chirish
ID orqali qidirish
Pagination
Sorting
Custom query yozish

Boshlang'ich bosqichda eng muhimi - CRUD.

5. Kerakli dependency

Spring Initializr’da quyidagilarni tanlaymiz:

Spring Web
Spring Data JPA
H2 Database
Lombok

Maven’da shunday bo‘ladi:

<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>

6. H2 Database nima?

H2 - yengil, in-memory database.

In-memory degani:

Database RAM ichida ishlaydi. App o‘chsa, data ham o‘chishi mumkin.

H2 boshlang'ich uchun juda qulay, chunki PostgreSQL yoki MySQL o‘rnatmasdan JPA’ni o‘rganish mumkin.

Real production’da esa odatda:

PostgreSQL
MySQL
Oracle
MS SQL Server

ishlatiladi.

7. application.properties sozlamasi

H2 bilan ishlash uchun:

spring.application.name=jpa-demo

spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driver-class-name=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=

spring.h2.console.enabled=true
spring.h2.console.path=/h2-console

spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true

Bu yerda:

8. H2 console’ga kirish

App ishga tushgandan keyin browserda:

http://localhost:8080/h2-console

Kirishda:

JDBC URL: jdbc:h2:mem:testdb
User Name: sa
Password: bo‘sh

Shu yerda table va datalarni ko‘rish mumkin.

9. @Entity nima?

@Entity - class database table bilan bog‘lanishini bildiradi.

import jakarta.persistence.Entity;
import jakarta.persistence.Id;

@Entity
public class User {

    @Id
    private Long id;

    private String name;
    private String email;
}

Bu degani:

User class database’da table sifatida ishlatiladi.

10. @Id nima?

@Id - primary key fieldni bildiradi.

Database’da har bir row’ni ajratib turadigan unique qiymat kerak.

@Id
private Long id;

Masalan:

Bu yerda id - primary key.

11. @GeneratedValue nima?

@GeneratedValue - ID avtomatik yaratilishini bildiradi.

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

Endi user yaratganda idni o‘zimiz bermaymiz. Database o‘zi beradi.

12. To‘liq Entity misol

package uz.jts.demo.entity;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;

@Entity
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;
    private String email;

    public User() {
    }

    public User(String name, String email) {
        this.name = name;
        this.email = email;
    }

    public Long getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getEmail() {
        return email;
    }

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

    public void setName(String name) {
        this.name = name;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

Muhim:

JPA entity’da no-args constructor bo‘lishi kerak.

Ya’ni:

public User() {
}

13. Lombok bilan Entity

Lombok ishlatsak kod qisqaradi:

package uz.jts.demo.entity;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

@Getter
@Setter
@NoArgsConstructor
@Entity
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;
    private String email;

    public User(String name, String email) {
        this.name = name;
        this.email = email;
    }
}

Lekin boshlang'ich bosqichda avval oddiy getter/setter bilan tushungan yaxshi.

14. @Table nima?

@Table - database table nomini aniq berish uchun ishlatiladi.

@Entity
@Table(name = "users")
public class User {
}

Agar @Table yozilmasa, table nomi odatda class nomidan olinadi.

Yaxshi amaliyot:

@Table(name = "users")

Nega users? Chunki user ba’zi database’larda reserved keyword bo‘lishi mumkin.

15. @Column nima?

@Column - field qaysi column bilan bog‘lanishini va uning qoidalarini belgilaydi.

@Column(name = "email", nullable = false, unique = true)
private String email;

Bu degani:

Column nomi: email
Null bo‘lishi mumkin emas
Unique bo‘lishi kerak

To‘liqroq misol:

@Column(name = "full_name", nullable = false, length = 100)
private String name;

16. Entity yaxshi yozilishi

package uz.jts.demo.entity;

import jakarta.persistence.*;

@Entity
@Table(name = "users")
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "full_name", nullable = false, length = 100)
    private String name;

    @Column(name = "email", nullable = false, unique = true)
    private String email;

    public User() {
    }

    public User(String name, String email) {
        this.name = name;
        this.email = email;
    }

    // getter/setter
}

17. JpaRepository nima?

JpaRepository - tayyor CRUD methodlar beradigan interface.

public interface UserRepository extends JpaRepository<User, Long> {
}

Bu yerda:

User - qaysi entity bilan ishlaydi
Long - User ID tipi

Shu bitta interface orqali ko‘p methodlar tayyor bo‘ladi.

18. JpaRepository tayyor methodlari

Misol:

List<User> users = userRepository.findAll();

Optional<User> user = userRepository.findById(1L);

User savedUser = userRepository.save(user);

userRepository.deleteById(1L);

19. Repository yozish

package uz.jts.demo.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import uz.jts.demo.entity.User;

public interface UserRepository extends JpaRepository<User, Long> {
}

Bu interface’ga @Repository yozish shart emas. Spring Data JPA o‘zi bean qiladi.

20. DTO nima uchun kerak?

Entity’ni to‘g‘ridan-to‘g‘ri API’da ishlatish boshlang'ich uchun mumkin, lekin professional loyihada DTO ishlatiladi.

Sababi:

Entity database modeli
DTO API request/response modeli

Yaxshi structure:

UserEntity       → database uchun
CreateUserRequest → POST body uchun
UserResponse     → clientga javob uchun

21. Request DTO

package uz.jts.demo.dto;

public record CreateUserRequest(
        String name,
        String email
) {
}

22. Response DTO

package uz.jts.demo.dto;

public record UserResponse(
        Long id,
        String name,
        String email
) {
}

23. Service yozish

package uz.jts.demo.service;

import org.springframework.stereotype.Service;
import uz.jts.demo.dto.CreateUserRequest;
import uz.jts.demo.dto.UserResponse;
import uz.jts.demo.entity.User;
import uz.jts.demo.repository.UserRepository;

import java.util.List;

@Service
public class UserService {

    private final UserRepository userRepository;

    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }

    public UserResponse createUser(CreateUserRequest request) {
        User user = new User(request.name(), request.email());

        User savedUser = userRepository.save(user);

        return new UserResponse(
                savedUser.getId(),
                savedUser.getName(),
                savedUser.getEmail()
        );
    }

    public List<UserResponse> getUsers() {
        return userRepository.findAll()
                .stream()
                .map(user -> new UserResponse(
                        user.getId(),
                        user.getName(),
                        user.getEmail()
                ))
                .toList();
    }
}

Bu yerda:

request → entity
entity database’ga saqlanadi
saved entity → response

24. Controller yozish

package uz.jts.demo.controller;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import uz.jts.demo.dto.CreateUserRequest;
import uz.jts.demo.dto.UserResponse;
import uz.jts.demo.service.UserService;

import java.util.List;

@RestController
@RequestMapping("/users")
public class UserController {

    private final UserService userService;

    public UserController(UserService userService) {
        this.userService = userService;
    }

    @PostMapping
    public ResponseEntity<UserResponse> createUser(
            @RequestBody CreateUserRequest request
    ) {
        UserResponse response = userService.createUser(request);

        return ResponseEntity
                .status(HttpStatus.CREATED)
                .body(response);
    }

    @GetMapping
    public List<UserResponse> getUsers() {
        return userService.getUsers();
    }
}

25. Test qilish

POST user yaratish

POST http://localhost:8080/users
Content-Type: application/json

Body:

{
  "name": "Ali",
  "email": "ali@mail.com"
}

Response:

{
  "id": 1,
  "name": "Ali",
  "email": "ali@mail.com"
}

GET users

GET http://localhost:8080/users

Response:

[
  {
    "id": 1,
    "name": "Ali",
    "email": "ali@mail.com"
  }
]

26. findById bilan bitta user olish

Service:

public UserResponse getUserById(Long id) {
    User user = userRepository.findById(id)
            .orElseThrow(() -> new RuntimeException("User topilmadi"));

    return new UserResponse(
            user.getId(),
            user.getName(),
            user.getEmail()
    );
}

Controller:

@GetMapping("/{id}")
public UserResponse getUserById(@PathVariable Long id) {
    return userService.getUserById(id);
}

Request:

GET /users/1

27. save() update ham qila oladi

save() ikki xil ishlaydi:

Update service:

public UserResponse updateUser(Long id, CreateUserRequest request) {
    User user = userRepository.findById(id)
            .orElseThrow(() -> new RuntimeException("User topilmadi"));

    user.setName(request.name());
    user.setEmail(request.email());

    User updatedUser = userRepository.save(user);

    return new UserResponse(
            updatedUser.getId(),
            updatedUser.getName(),
            updatedUser.getEmail()
    );
}

Controller:

@PutMapping("/{id}")
public UserResponse updateUser(
        @PathVariable Long id,
        @RequestBody CreateUserRequest request
) {
    return userService.updateUser(id, request);
}

28. Delete qilish

Service:

public void deleteUser(Long id) {
    if (!userRepository.existsById(id)) {
        throw new RuntimeException("User topilmadi");
    }

    userRepository.deleteById(id);
}

Controller:

@DeleteMapping("/{id}")
public ResponseEntity<Void> deleteUser(@PathVariable Long id) {
    userService.deleteUser(id);
    return ResponseEntity.noContent().build();
}

Response:

204 No Content

29. To‘liq CRUD API

Endpointlar:

POST   /users
GET    /users
GET    /users/{id}
PUT    /users/{id}
DELETE /users/{id}

Layerlar:

UserController → UserService → UserRepository → H2 Database

Bu boshlang'ich bosqich uchun juda yaxshi birinchi real backend API.

30. Package structure

Tavsiya qilinadigan structure:

uz.jts.demo
 ├── DemoApplication.java
 ├── controller
 │   └── UserController.java
 ├── service
 │   └── UserService.java
 ├── repository
 │   └── UserRepository.java
 ├── entity
 │   └── User.java
 └── dto
     ├── CreateUserRequest.java
     └── UserResponse.java

31. ddl-auto nima?

spring.jpa.hibernate.ddl-auto=update

Bu Hibernate table’larni qanday boshqarishini bildiradi.

Eng ko‘p uchraydigan qiymatlar:

boshlang'ich bosqich uchun H2'da:

spring.jpa.hibernate.ddl-auto=update

yoki:

spring.jpa.hibernate.ddl-auto=create-drop

Production’da ehtiyot bo‘lish kerak. Real loyihada Flyway yoki Liquibase ishlatiladi.

32. show-sql nima?

spring.jpa.show-sql=true

Bu Hibernate ishlatayotgan SQL querylarni console’da ko‘rsatadi.

Masalan:

insert into users (email, full_name, id) values (?, ?, default)
select u1_0.id, u1_0.email, u1_0.full_name from users u1_0

boshlang'ich bosqich uchun foydali, chunki JPA orqada qanday SQL ishlatayotganini ko‘rasan.

33. Derived query methods

Spring Data JPA method nomidan query yasay oladi.

Repository:

public interface UserRepository extends JpaRepository<User, Long> {

    Optional<User> findByEmail(String email);

    List<User> findByName(String name);

    boolean existsByEmail(String email);
}

Bu methodlar uchun SQL yozmaymiz. Spring nomidan tushunadi.

Misollar:

34. Email unique tekshirish

Service’da:

public UserResponse createUser(CreateUserRequest request) {
    if (userRepository.existsByEmail(request.email())) {
        throw new RuntimeException("Bu email allaqachon mavjud");
    }

    User user = new User(request.name(), request.email());
    User savedUser = userRepository.save(user);

    return new UserResponse(
            savedUser.getId(),
            savedUser.getName(),
            savedUser.getEmail()
    );
}

Repository:

public interface UserRepository extends JpaRepository<User, Long> {

    boolean existsByEmail(String email);
}

35. Eng ko‘p uchraydigan xatolar

1. @Entity unutish

Xato:

public class User {
}

To‘g‘ri:

@Entity
public class User {
}

2. @Id unutish

Xato:

@Entity
public class User {
    private Long id;
}

To‘g‘ri:

@Entity
public class User {
    @Id
    private Long id;
}

3. No-args constructor yo‘q

Xato:

@Entity
public class User {

    public User(String name) {
        this.name = name;
    }
}

To‘g‘ri:

public User() {
}

4. Repository generics noto‘g‘ri

Xato:

public interface UserRepository extends JpaRepository<User, Integer> {
}

Agar entity’da ID Long bo‘lsa, to‘g‘ri:

public interface UserRepository extends JpaRepository<User, Long> {
}

5. Entity’ni API’da to‘g‘ridan-to‘g‘ri qaytarish

boshlang'ich bosqich uchun ishlaydi, lekin production’da tavsiya qilinmaydi.

Yaxshiroq:

Entity → Response DTO
Request DTO → Entity

36. Interview uchun javoblar

Savol: Spring Data JPA nima?

Spring Data JPA - JPA asosida database bilan ishlashni osonlashtiradigan Spring moduli. U repository interface orqali CRUD methodlarni tayyor beradi.

Savol: @Entity nima?

@Entity class database table bilan mapping qilinishini bildiradi.

Savol: @Id nima?

@Id entity’dagi primary key fieldni bildiradi.

Savol: @GeneratedValue nima?

@GeneratedValue ID avtomatik generatsiya qilinishini bildiradi.

Savol: JpaRepository<User, Long> nimani bildiradi?

Bu repository User entity bilan ishlaydi va uning ID tipi Long ekanini bildiradi.

Savol: save() nima qiladi?

save() entity’ni database’ga saqlaydi. Agar ID yangi bo‘lsa insert qiladi, mavjud entity bo‘lsa update qiladi.

37. Java developer uchun xulosa

Bugungi mavzudan eslab qol:

Spring Data JPA - database bilan ishlashni osonlashtiradi
JPA - Java object va database table orasidagi mapping standarti
Hibernate - JPA implementation
@Entity - classni table qiladi
@Id - primary key
@GeneratedValue - ID avtomatik yaratiladi
@Table - table nomini sozlaydi
@Column - column qoidalarini sozlaydi
JpaRepository - tayyor CRUD methodlar beradi
H2 - boshlang'ich bosqich uchun yengil test database
DTO - API request/response modeli

38. Amaliy vazifa

Product CRUD API yoz:

Entity

Product
- id
- name
- price

Endpointlar

POST   /products
GET    /products
GET    /products/{id}
PUT    /products/{id}
DELETE /products/{id}

Package structure

controller
service
repository
entity
dto

Qo‘shimcha

Repository’da method yoz:

boolean existsByName(String name);

Product yaratishda nomi oldin mavjud bo‘lsa, xato qaytar.