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HB CRUD
Hibernate makes it easy to perform CRUD operations using Session and Transaction. In this section, we'll cover:
- Create (Insert Data)
- Read (Retrieve Data)
- Update (Modify Data)
- Delete (Remove Data)
Entity Class with Mappings:
Student.java
import jakarta.persistence.*;
@Entity
@Table(name = "students")
public class Student {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
@Column(name = "student_name", nullable = false)
private String name;
@Column(unique = true)
private String email;
// Constructors
public Student() {}
public Student(String name, String email) {
this.name = name;
this.email = email;
}
// Getters and Setters
public Long getId() { return id; }
public void setId(Long id) { this.id = id; }
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public String getEmail() { return email; }
public void setEmail(String email) { this.email = email; }
}
Create (Insert Data):
To insert a new record into the database, we use the persist() method.
Main.java
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
public class Main {
public static void main(String[] args) {
// Create a new student
Student student = new Student("Alice", "alice@example.com");
// Create Hibernate session
SessionFactory sessionFactory = new Configuration().configure("hibernate.cfg.xml").addAnnotatedClass(Student.class).buildSessionFactory();
Session session = sessionFactory.openSession();
Transaction transaction = session.beginTransaction();
// Save the student
session.persist(student); // Hibernate will generate an INSERT SQL statement
transaction.commit();
session.close();
sessionFactory.close();
System.out.println("Student saved successfully!");
}
}
Read (Retrieve Data):
To fetch data, we use get() methods.
Main.java
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class Main {
public static void main(String[] args) {
// Create Hibernate session
SessionFactory sessionFactory = new Configuration().configure("hibernate.cfg.xml").addAnnotatedClass(Student.class).buildSessionFactory();
Session session = sessionFactory.openSession();
// Fetch student with ID 1
Student student = session.get(Student.class, 1L);
if (student != null) {
System.out.println("Student Name: " + student.getName());
} else {
System.out.println("Student not found!");
}
session.close();
sessionFactory.close();
System.out.println("Student saved successfully!");
}
}
Update (Modify Data)
To update a record, we use the merge() method.
Main.java
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
public class Main {
public static void main(String[] args) {
// Create Hibernate session
SessionFactory sessionFactory = new Configuration().configure("hibernate.cfg.xml").addAnnotatedClass(Student.class).buildSessionFactory();
Session session = sessionFactory.openSession();
Transaction transaction = session.beginTransaction();
// Fetch student from DB
Student student = session.get(Student.class, 1L);
if (student != null) {
student.setEmail("newemail@example.com"); // Update email
session.merge(student); // Hibernate generates an UPDATE SQL statement
transaction.commit();
System.out.println("Student updated successfully!");
} else {
System.out.println("Student not found!");
}
session.close();
sessionFactory.close();
}
}
Delete (Remove Data)
To delete a record, we use the remove() method.
Main.java
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
public class Main {
public static void main(String[] args) {
// Create Hibernate session
SessionFactory sessionFactory = new Configuration().configure("hibernate.cfg.xml").addAnnotatedClass(Student.class).buildSessionFactory();
Session session = sessionFactory.openSession();
Transaction transaction = session.beginTransaction();
// Fetch student from DB
Student student = session.get(Student.class, 1L);
if (student != null) {
session.remove(student); // Hibernate generates DELETE SQL statement
transaction.commit();
System.out.println("Student deleted successfully!");
} else {
System.out.println("Student not found!");
}
session.close();
sessionFactory.close();
}
}