At the beginning of using the spring boot development project, the Spring Data JPA used by the ORM framework was only used intermittently for more than a year, without making some summary. Taking advantage of the current serious epidemic situation and little work, I will take a note and record the general steps of integrating Spring Data JPA with spring boot.
1. First, create a new springboot project named springdata. The version of springboot uses 2.0.5.RELEASE.

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.5.RELEASE</version>
    <relativePath/>
</parent>

2. Import the corresponding jar package

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>

    <!-- mysql -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
</dependencies>

3. Create a new User entity class and add comments

import lombok.Data;
import lombok.ToString;
import javax.persistence.*;
import java.io.Serializable;

@Data
@Entity
@Table(name = "user")
@ToString
public class User implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    @Column(name = "user_name")
    private String userName;
    @Column(name = "user_age")
    private Integer userAge;
}

Note:
@Entity: indicates that the class is an entity class
@Table: indicates the table name of the database
@Id: Specifies the primary key of the table
@Generated value: Specifies the generation policy of the primary key
@Column: indicates the correspondence between the member properties of the class and the fields in the table
4. Create a new UserDao interface, integrate the JpaRepository class, add the sel method to query users, and update the user update method

import com.springdata.model.User;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Modifying;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;

@Repository
public interface UserDao extends JpaRepository<User, Integer> {
    @Query(value = "select id, user_name, user_age from user where id = :id", nativeQuery = true)
    User sel(@Param("id") int id);

    @Transactional
    @Modifying
    @Query(value = "update user set user_name = :userName, user_age = :userAge where id = :id", nativeQuery = true)
    void update(@Param("userName") String userName, @Param("userAge") Integer userAge, @Param("id") Integer id);
}

5. Add mysql database configuration and jpa configuration under application.properties configuration file in resources directory

server.port=8080

# mysql database configuration
spring.datasource.url=jdbc:mysql://localhost:3306/test
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

# JPA configuration
# Show executed sql statements
spring.jpa.show-sql=true

6. Create UserService interface class and implementation class UserServiceImpl

import com.springdata.model.User;
import java.util.List;

public interface UserService {
    public User sel(int id);
    public void add(User user);
    public void update(User user);
}

import com.springdata.dao.UserDao;
import com.springdata.model.User;
import com.springdata.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;

@Service
public class UserServiceImpl implements UserService {
    @Autowired
    private UserDao userDao;

    @Override
    public User sel(int id) {
        return userDao.sel(id);
    }

    @Override
    public void add(User user) {
        userDao.save(user);
    }

    @Override
    public void update(User user) {
        userDao.update(user.getUserName(), user.getUserAge(), user.getId());
    }
}

7. Create controller class UserController

import com.springdata.model.User;
import com.springdata.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import java.util.List;

@RestController
@RequestMapping("/user")
public class UserController {
    @Autowired
    private UserService userService;

    @GetMapping(value = "/getUser/{id}")
    public String getUser(@PathVariable int id) {
        return userService.sel(id).toString();
    }

    @PostMapping(value = "/addUser", produces = "application/json;charset=UTF-8")
    public String addUser(@RequestBody User user) {
        try {
            userService.add(user);
        } catch (Exception e) {
            e.printStackTrace();
            return "error";
        }
        return "success";
    }

    @PostMapping(value = "/updateUser", produces = "application/json;charset=UTF-8")
    public String updateUser(@RequestBody User user) {
        try {
            userService.update(user);
        } catch (Exception e) {
            e.printStackTrace();
            return "error";
        }
        return "success";
    }
}

8. Create the user table under the test library of mysql

CREATE TABLE `user` (
	`id` INT(32) NOT NULL AUTO_INCREMENT,
	`user_name` VARCHAR(32) NOT NULL,
	`user_age` INT(3) NOT NULL,
	PRIMARY KEY (`id`) USING BTREE
)

9. Start the spring data project and test with postman
New users:

Modify user:

Query user:

So far, the integration of Spring Data JPA with spring boot has been completed, and the test is also very successful, isn't it very simple!
I hope you can make some improvements. Thank you very much!