Many Apache projects support interaction with a relational database. Creating a new connection for each user can be time consuming (often requiring multiple seconds of clock time), in order to perform a database transaction that might take milliseconds. Opening a connection per user can be unfeasible in a publicly-hosted Internet application where the number of simultaneous users can be very large. Accordingly, developers often wish to share a "pool" of open connections between all of the application's current users. The number of users actually performing a request at any given time is usually a very small percentage of the total number of active users, and during request processing is the only time that a database connection is required. The application itself logs into the DBMS, and handles any user account issues internally.
There are several Database Connection Pools already available, both within Apache products and elsewhere. This Commons package provides an opportunity to coordinate the efforts required to create and maintain an efficient, feature-rich package under the ASF license.
The commons-dbcp2 package relies on code in the commons-pool2 package to provide the underlying object pool mechanisms that it utilizes.
DBCP now comes in three different versions to support different versions of JDBC. Here is how it works:
DBCP 2 binaries should be used by applications running under Java 7.
DBCP 1.4 binaries should be used by applications running under Java 6.
DBCP 1.3 should be used when running under Java 1.4 5.
DBCP 2 is based on Commons Pool 2 and provides increased performance, JMX support as well as numerous other new features compared to DBCP 1.x. Users upgrading to 2.x should be aware that the Java package name has changed, as well as the Maven co-ordinates, since DBCP 2.x is not binary compatible with DBCP 1.x. Users should also be aware that some configuration options (e.g. maxActive to maxTotal) have been renamed to align them with the new names used by Commons Pool 2.
There is no difference in the codebase supporting DBCP 1.4.x and 1.3.x other than that the code implementing methods added to support JDBC 4 has been filtered out of the DBCP 1.3 sources.
See the downloads page for information on obtaining releases.