Warn Sessionimpl:3355 - Finalizing Unclosed Session With Closed Co Nnection

6 min read Sep 30, 2024

Understanding and Solving the "WARN sessionimpl:3355 - finalizing unclosed session with closed connection" Error in Hibernate

Have you ever encountered the error message "WARN sessionimpl:3355 - finalizing unclosed session with closed connection" while working with Hibernate? This message indicates a potential issue in your application's interaction with the database. It might not seem alarming at first, but it can contribute to performance bottlenecks and unexpected behavior in the long run.

Let's delve into the root causes of this warning, explore potential solutions, and learn how to prevent it from appearing in your future Hibernate projects.

What Does the Error Mean?

The error message "WARN sessionimpl:3355 - finalizing unclosed session with closed connection" signifies that a Hibernate session was not properly closed before the underlying connection to the database was closed.

This occurs when:

A Hibernate session object is created but not explicitly closed. This can happen due to missing or incorrect session.close() or session.flush() calls in your code.
The connection to the database is closed prematurely. This could be caused by an external factor such as a network interruption, a connection pool exhaustion, or a manual closure of the connection.

Why is This a Problem?

While this warning might seem benign, it's important to address it for a few reasons:

Resource Leaks: Unclosed sessions can hold onto database resources, leading to connection pool exhaustion and performance issues.
Data Integrity Issues: Incomplete transactions caused by unclosed sessions can lead to inconsistent data in the database.
Transaction Isolation Problems: Open sessions can interfere with other transactions accessing the same data, potentially resulting in unexpected concurrency issues.

How to Solve the "WARN sessionimpl:3355 - finalizing unclosed session with closed connection" Issue

Here are some common solutions and best practices to address this error:

1. Ensure Proper Session Management:

Utilize the try-with-resources construct: The try-with-resources statement is an excellent approach to ensure sessions are automatically closed.

try (Session session = sessionFactory.openSession()) {
    // Your database operations using the session here
}

Use a finally block: If you can't use try-with-resources, ensure that you close the session within a finally block.

Session session = sessionFactory.openSession();
try {
    // Your database operations using the session here
} finally {
    if (session != null && session.isOpen()) {
        session.close();
    }
}

2. Handle Connection Closing Carefully:

Avoid manual connection closure: Let Hibernate manage connections. Do not close the underlying JDBC connection directly unless absolutely necessary.
Use a connection pool: Implementing a connection pool will ensure that connections are efficiently managed and reused, preventing premature closure.

3. Implement Transaction Management:

Use Hibernate's transaction management features: Utilize the Transaction interface to manage transactions, ensuring the session is properly closed and the transaction is committed or rolled back.

try (Session session = sessionFactory.openSession()) {
    Transaction tx = session.beginTransaction();
    try {
        // Your database operations using the session here
        tx.commit();
    } catch (Exception e) {
        if (tx != null) {
            tx.rollback();
        }
        throw e;
    }
}

4. Monitor and Analyze:

Logging and debugging: Use Hibernate's logging capabilities or a debugger to identify where sessions are not being closed correctly.

Important Considerations

Hibernate's SessionFactory: The SessionFactory is responsible for creating and managing sessions. Make sure you close the SessionFactory when it's no longer needed to release resources.
Thread Safety: Ensure your sessions are not accessed by multiple threads concurrently, as this can lead to unpredictable behavior and errors.
Use a framework for transaction management: Frameworks like Spring or JTA can simplify transaction management and reduce the risk of forgetting to close sessions or handle transactions properly.

Conclusion

The "WARN sessionimpl:3355 - finalizing unclosed session with closed connection" message should be addressed promptly to prevent performance bottlenecks and potential data integrity issues. By adopting best practices for session management, using transaction management tools, and carefully handling connections, you can avoid this warning and ensure your Hibernate applications run smoothly and efficiently. Remember, proper resource management is crucial for creating reliable and robust Hibernate applications.