Introduction to Hibernate

Hibernate is an open-source object-relational mapping (ORM) framework for Java. It provides a framework for mapping Java objects to relational database tables and vice versa. The main goal of Hibernate is to simplify the process of persisting objects and working with databases.

One of the key advantages of using Hibernate is that it abstracts away the differences between different database vendors and provides a consistent API for interacting with databases, regardless of the underlying database technology.

Let's take a look at a simple example of how Hibernate can be used to map a Java object to a database table:

1@Entity
2public class Employee {
3
4    @Id
5    @GeneratedValue(strategy = GenerationType.IDENTITY)
6    private Long id;
7    private String name;
8    private String department;
9    private double salary;
10
11    // getters and setters
12
13    // toString
14
15}

In this example, we have defined an Employee class as an entity using the @Entity annotation. This tells Hibernate that this class should be persisted in a database table.

The @Id annotation is used to indicate the primary key field of the entity. In this case, the primary key is generated automatically using the @GeneratedValue annotation with the GenerationType.IDENTITY strategy.

Hibernate provides various annotations that can be used to map different types of relationships between entities, define custom queries, and more. We will explore these annotations in more detail in later sections.

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import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.GenerationType;

import javax.persistence.Id;

​

@Entity

public class Employee {

​

    @Id

    @GeneratedValue(strategy = GenerationType.IDENTITY)

    private Long id;

    private String name;

    private String department;

    private double salary;

​

    // getters and setters

​

    // toString

​

}