Should You Close JDBC Connections in a Connection Pool?

Closing JDBC Connections in Pool: A Detailed Explanation

When using JDBC in a pooled environment, the question of whether to close connections often arises. This article provides a thorough analysis of this topic, addressing common misconceptions and offering practical guidance.

Question 1: Should Connections Be Closed in Connection Pools?

Yes, it is essential to close pooled connections. Contrary to common belief, closing connections does not negate the purpose of pooling. Instead, it serves a crucial role:

• Wrapper Interface: Pooled connections are wrappers around actual connections. Closing them releases the underlying connection back to the pool, making it available for reuse.
• Pool Management: Closing connections signals the pool to manage resource allocation effectively. It allows the pool to determine if the released connection should be closed or reused for subsequent getConnection() calls.

Question 2: Standard Connection Pooling Method

The presented method for obtaining a connection raises concerns:

• Overly Complex: It attempts to locate a DataSource in the runtime environment. This introduces unnecessary complexity and uncertainty.
• Initialization Ambiguity: It is unclear when and how the DataSource is initialized, leading to potential issues with multiple executions and unexpected behavior.

Recommended Practice:

For secure and efficient connection pooling, it is recommended to:

1. Initialize the DataSource once at application startup in a dedicated initialization class.
2. Call getConnection() consistently on the same DataSource.
3. Close all JDBC resources in reversed order in a finally block. By following these guidelines, you can leverage connection pooling effectively while maintaining data integrity and performance.

Additional Resources:

• [Is it safe to use a static java.sql.Connection instance in a multithreaded system?](https://stackoverflow.com/questions/789045/is-it-safe-to-use-a-static-java-sql-connection-instance-in-a-multithreaded-system)
• [Am I Using JDBC Connection Pooling?](https://stackoverflow.com/questions/4407074/am-i-using-jdbc-connection-pooling)

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