What is Hibernate? How does it works

Hibernate is an open-source Object-Relational Mapping (ORM) framework for Java. It simplifies database interactions by allowing developers to work with Java objects instead of SQL queries. This abstraction reduces the complexity of data manipulation and helps in managing database connections efficiently.

How Does Hibernate Work?

Hibernate works by mapping Java classes to database tables and Java data types to SQL data types. Here’s a simplified overview of how it operates:

1. Configuration: Set up Hibernate configuration file (hibernate.cfg.xml) with database connection details.
2. Session Factory: Create a SessionFactory object that manages sessions for interacting with the database.
3. Session: Open a session from the SessionFactory to perform CRUD operations.
4. Transactions: Use transactions to ensure data integrity when performing multiple operations.
5. Querying: Use Hibernate Query Language (HQL) or Criteria API for querying data.
6. Closing Session: Always close the session to free up resources.

Example

    <span>// Hibernate configuration</span>
    <span>Configuration</span> <span>configuration</span> <span>=</span> <span>new</span> <span>Configuration</span><span>().</span><span>configure</span><span>();</span>
    <span>// Build session factory</span>
    <span>SessionFactory</span> <span>sessionFactory</span> <span>=</span> <span>configuration</span><span>.</span><span>buildSessionFactory</span><span>();</span>
    <span>// Open session</span>
    <span>Session</span> <span>session</span> <span>=</span> <span>sessionFactory</span><span>.</span><span>openSession</span><span>();</span>
    <span>// Begin transaction</span>
    <span>Transaction</span> <span>transaction</span> <span>=</span> <span>session</span><span>.</span><span>beginTransaction</span><span>();</span>
    <span>// Save an entity</span>
    <span>MyEntity</span> <span>entity</span> <span>=</span> <span>new</span> <span>MyEntity</span><span>();</span>
    <span>entity</span><span>.</span><span>setName</span><span>(</span><span>"Example"</span><span>);</span>
    <span>session</span><span>.</span><span>save</span><span>(</span><span>entity</span><span>);</span>
    <span>// Commit transaction</span>
    <span>transaction</span><span>.</span><span>commit</span><span>();</span>
    <span>// Close session</span>
    <span>session</span><span>.</span><span>close</span><span>();</span>
    <span>// Hibernate configuration</span>
    <span>Configuration</span> <span>configuration</span> <span>=</span> <span>new</span> <span>Configuration</span><span>().</span><span>configure</span><span>();</span>

    <span>// Build session factory</span>
    <span>SessionFactory</span> <span>sessionFactory</span> <span>=</span> <span>configuration</span><span>.</span><span>buildSessionFactory</span><span>();</span>

    <span>// Open session</span>
    <span>Session</span> <span>session</span> <span>=</span> <span>sessionFactory</span><span>.</span><span>openSession</span><span>();</span>

    <span>// Begin transaction</span>
    <span>Transaction</span> <span>transaction</span> <span>=</span> <span>session</span><span>.</span><span>beginTransaction</span><span>();</span>

    <span>// Save an entity</span>
    <span>MyEntity</span> <span>entity</span> <span>=</span> <span>new</span> <span>MyEntity</span><span>();</span>
    <span>entity</span><span>.</span><span>setName</span><span>(</span><span>"Example"</span><span>);</span>
    <span>session</span><span>.</span><span>save</span><span>(</span><span>entity</span><span>);</span>

    <span>// Commit transaction</span>
    <span>transaction</span><span>.</span><span>commit</span><span>();</span>

    <span>// Close session</span>
    <span>session</span><span>.</span><span>close</span><span>();</span>
    // Hibernate configuration
    Configuration configuration = new Configuration().configure();

    // Build session factory
    SessionFactory sessionFactory = configuration.buildSessionFactory();

    // Open session
    Session session = sessionFactory.openSession();

    // Begin transaction
    Transaction transaction = session.beginTransaction();

    // Save an entity
    MyEntity entity = new MyEntity();
    entity.setName("Example");
    session.save(entity);

    // Commit transaction
    transaction.commit();

    // Close session
    session.close();

Enter fullscreen mode Exit fullscreen mode

Conclusion

In summary, Hibernate is a powerful tool for Java developers that streamlines database operations through ORM. By abstracting the complexities of SQL, it allows developers to focus on their application logic while ensuring efficient data management.

原文链接：What is Hibernate? How does it works