Chapter 11. Connection Pools and Data Sources

Table of Contents

• Overview
• Application Servers: ConnectionPoolDataSource
• Applications: DataSource
• Tomcat setup
• Data Sources and JNDI

JDBC 2 introduced standard connection pooling features in an add-on API known as the JDBC 2.0 Optional Package (also known as the JDBC 2.0 Standard Extension). These features have since been included in the core JDBC 3 API.

Overview

The JDBC API provides a client and a server interface for connection pooling. The client interface is javax.sql.DataSource, which is what application code will typically use to acquire a pooled database connection. The server interface is javax.sql.ConnectionPoolDataSource, which is how most application servers will interface with the PostgreSQL™ JDBC driver.

In an application server environment, the application server configuration will typically refer to the PostgreSQL™ ConnectionPoolDataSource implementation, while the application component code will typically acquire a DataSource implementation provided by the application server (not by PostgreSQL™).

For an environment without an application server, PostgreSQL™ provides two implementations of DataSource which an application can use directly. One implementation performs connection pooling, while the other simply provides access to database connections through the DataSource interface without any pooling. Again, these implementations should not be used in an application server environment unless the application server does not support the ConnectionPoolDataSource interface.