<dependency>
<groupId>javax.persistence</groupId>
<artifactId>javax.persistence-api</artifactId>
<version>2.2</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>5.5.6.Final</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.11</version>
</dependency>
package com.example.entity;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
@Entity
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
private String email;
}
package com.example.dao;
import com.example.entity.User;
public interface UserDao {
User findById(Long id);
User save(User user);
void delete(User user);
}
package com.example.dao.impl;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;
import com.example.dao.UserDao;
import com.example.entity.User;
@Repository
@Transactional
public class UserDaoImpl implements UserDao {
@PersistenceContext
private EntityManager entityManager;
@Override
public User findById(Long id) {
return entityManager.find(User.class, id);
}
@Override
public User save(User user) {
if (user.getId() == null) {
entityManager.persist(user);
return user;
} else {
return entityManager.merge(user);
}
}
@Override
public void delete(User user) {
entityManager.remove(user);
}
}
spring.datasource.url=jdbc:mysql://localhost:3306/mydatabase
spring.datasource.username=root
spring.datasource.password=password
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true
package com.example;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import com.example.dao.UserDao;
import com.example.entity.User;
@SpringBootApplication
public class App {
public static void main(String[] args) {
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(App.class);
UserDao userDao = context.getBean(UserDao.class);
User newUser = new User();
newUser.setName("John Doe");
newUser.setEmail("john.doe@example.com");
userDao.save(newUser);
User existingUser = userDao.findById(newUser.getId());
existingUser.setName("Jane Doe");
userDao.save(existingUser);
User deleteUser = userDao.findById(existingUser.getId());
userDao.delete(deleteUser);
context.close();
}
}
