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HB CRUD

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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();

}

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