Basic CRUD operations with Hibernate 6 involve creating, reading, updating, and deleting records in a database using Hibernate ORM. Hibernate simplifies these operations through its API.

Below is an explanation of each CRUD operation along with corresponding examples:

1. Create (Insert)

To save a new object in the database, you use the persist() or save() method provided by Hibernate.

SessionFactory factory = new Configuration()
                .configure("hibernate.cfg.xml")
                .addAnnotatedClass(Student.class)
                .buildSessionFactory();

try (Session session = factory.openSession()) {
    // Create a new student entity
    Student student = new Student("Jane Doe");

    // Start a transaction
    session.beginTransaction();

    // Save the entity to the database
    session.persist(student);

    // Commit the transaction
    session.getTransaction().commit();

    System.out.println("Student saved successfully with ID: " + student.getId());
} finally {
    factory.close();
}

2. Read (Retrieve)

Hibernate’s get() or find() method is used to retrieve data from the database. You can fetch an object by its primary key.

try (Session session = factory.openSession()) {
    // Start a transaction (optional if only querying)
    session.beginTransaction();

    // Retrieve a student by their primary key (ID)
    int studentId = 1;  // Example ID
    Student retrievedStudent = session.get(Student.class, studentId);

    System.out.println("Retrieved Student: " + retrievedStudent);

    // Commit the transaction
    session.getTransaction().commit();
}

3. Update

To modify an existing object in the database, you first retrieve it, make changes to its fields, and then let Hibernate update it within a transaction.

try (Session session = factory.openSession()) {
    // Start a transaction
    session.beginTransaction();

    // Retrieve the student entity we want to update
    int studentId = 1;  // Example ID
    Student studentToUpdate = session.get(Student.class, studentId);

    // Modify the entity (e.g., update the name)
    if (studentToUpdate != null) {
        studentToUpdate.setName("Updated Name");
    }

    // Hibernate automatically tracks changes and applies them during commit
    session.getTransaction().commit();

    System.out.println("Student updated successfully.");
}

4. Delete

To delete an object, retrieve it first and use the delete() method to remove it from the database.

try (Session session = factory.openSession()) {
    // Start a transaction
    session.beginTransaction();

    // Retrieve the student to delete by their primary key
    int studentId = 1;
    Student studentToDelete = session.get(Student.class, studentId);

    // Delete the entity if it exists
    if (studentToDelete != null) {
        session.delete(studentToDelete);
        System.out.println("Student deleted successfully.");
    }

    // Commit the transaction
    session.getTransaction().commit();
}

Keynotes for Hibernate 6:

1. Ensure you have the correct Hibernate dependencies in pom.xml (for Maven) or build.gradle (for Gradle).
2. You must configure hibernate.cfg.xml, including database connection properties and mapping annotated classes.
3. Always manage your Hibernate Session and SessionFactory carefully, and close them when done to free resources.
4. Hibernate 6 has slight differences in config (e.g., Jakarta imports). Ensure you’re using the correct versions of annotations and configs (jakarta.persistence instead of javax.persistence).

For the provided code, it already demonstrates correct usage of creating a SessionFactory, opening a Session, performing a transaction for persist(), and closing resources. The same principles apply for all CRUD operations—use beginTransaction(), perform the operation, and commit() the transaction.

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Maven Dependencies

<dependencies>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>6.4.4.Final</version>
    </dependency>
</dependencies>