What Is Database Connection Pool

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∟What Is Database Connection Pool

This section provides a quick introduction on database connection pool, which is an object container managing a set of JDBC connection objects to be reused to avoid repeated connection opening and closing operations.

What Is Database Connection Pool? - A Database Connection Pool is an object container that manages a set of JDBC connection objects to be reused to avoid repeated connection opening and closing operations.

There two main situations where you should consider using JDBC pooled connections:

Open and close connections frequently - A busy application server may need to handle thousands of requests in a short period of time. And all requests need to use database connections to access application data.
Complex database connections - An application may need to connect to a remote database server passing through multiple communication layers like: user authentications, security policies, firewalls, virtual machines, proxies, load balancers, etc.

The JDBC API 3.0 and newer versions provide a general interface for connection pooling with 3 primary classes:

javax.sql.PooledConnection - A physical connection to a data source.
avax.sql.ConnectionPooledDataSource - A factory for avax.sql.PooledConnection objects
ConnectionEventListener - An object to be notified of events generated by a PooledConnection object.

The actual implementation of the Connection Pool interface will be done by JDBC drivers or third party libraries.

Commonly used third party Connection Pool libraries are:

Commons DBCP - A JDBC database connection pool library developed by Apache See Commons DBCP Website at https://commons.apache.org/proper/commons-dbcp.

C3P0 - A mature and highly concurrent JDBC Connection pooling library developed by Steve Waldman. See C3P0 GitHub Website at https://github.com/swaldman/c3p0.