Usage of the Tomcat connection pool has been made to be as simple as possible, for those of you that are familiar with commons-dbcp, the transition will be very simple. Moving from other connection pools is also fairly straight forward.
Additional features
The Tomcat connection pool offers a few additional features over what most other pools let you do:
- initSQL – the ability to run a SQL statement exactly once, when the connection is created
- validationInterval – in addition to running validations on connections, avoid running them too frequently.
- jdbcInterceptors – flexible and pluggable interceptors to create any customizations around the pool, the query execution and the result set handling. More on this in the advanced section.
- fairQueue – Set the fair flag to true to achieve thread fairness or to use asynchronous connection retrieval
Inside the Apache Tomcat Container
The Tomcat Connection pool is configured as a resource described in The Tomcat JDBC documentation With the only difference being that you have to specify the factory attribute and set the value toorg.apache.tomcat.jdbc.pool.DataSourceFactory
Standalone
The connection pool only has another dependency, and that is on tomcat-juli.jar. To configure the pool in a stand alone project using bean instantiation, the bean to instantiate isorg.apache.tomcat.jdbc.pool.DataSource. The same attributes (documented below) as you use to configure a connection pool as a JNDI resource, are used to configure a data source as a bean.
JMX
The connection pool object exposes an MBean that can be registered. In order for the connection pool object to create the MBean, the flag jmxEnabled has to be set to true. This doesn’t imply that the pool will be registered with an MBean server, merely that the MBean is created. In a container like Tomcat, Tomcat itself registers the DataSource with the MBean server, the org.apache.tomcat.jdbc.pool.DataSource object will then register the actual connection pool MBean. If you’re running outside of a container, you can register the DataSource yourself under any object name you specify, and it propagates the registration to the underlying pool. To do this you would call mBeanServer.registerMBean(dataSource.getPool().getJmxPool(),objectname). Prior to this call, ensure that the pool has been created by calling dataSource.createPool().
