Usually, you want to have the SessionFactory create and pool JDBC connections for you. If you take this approach, opening a Session is as simple as:
Session session = sessions.openSession(); // open a new Session
As soon as you do something that requires access to the database, a JDBC connection will be obtained from the pool.
For this to work, we need to pass some JDBC connection properties to Hibernate. All Hibernate property names and semantics are defined on the class org.hibernate.cfg.Environment. We will now describe the most important settings for JDBC connection configuration.
Hibernate will obtain (and pool) connections using java.sql.DriverManager if you set the following properties:
|
Property name
|
Purpose
|
hibernate.connection.driver_class
|
jdbc driver class
|
hibernate.connection.url
|
jdbc URL
|
hibernate.connection.username
|
database user
|
hibernate.connection.password
|
database user password
|
hibernate.connection.pool_size
|
maximum number of pooled connections
|
Table 3.1. Hibernate JDBC Properties
Hibernate's own connection pooling algorithm is however quite rudimentary. It is intended to help you get started and is
not intended for use in a production system
or even for performance testing. You should use a third party pool for best performance and stability. Just replace the hibernate.connection.pool_size property with connection pool specific settings. This will turn off Hibernate's internal pool. For example, you might like to use C3P0.
C3P0 is an open source JDBC connection pool distributed along with Hibernate in the lib directory. Hibernate will use its C3P0ConnectionProvider for connection pooling if you set hibernate.c3p0.* properties. If you'd like to use Proxool refer to the packaged hibernate.properties and the Hibernate web site for more information.
Here is an example hibernate.properties file for C3P0:
hibernate.connection.driver_class = org.postgresql.Driver
hibernate.connection.url = jdbc:postgresql://localhost/mydatabase
hibernate.connection.username = myuser
hibernate.connection.password = secret
hibernate.c3p0.min_size=5
hibernate.c3p0.max_size=20
hibernate.c3p0.timeout=1800
hibernate.c3p0.max_statements=50
hibernate.dialect = org.hibernate.dialect.PostgreSQLDialect
For use inside an application server, you should almost always configure Hibernate to obtain connections from an application server Datasource registered in JNDI. You'll need to set at least one of the following properties:
|
Propery name
|
Purpose
|
hibernate.connection.datasource
|
datasource JNDI name
|
hibernate.jndi.url
|
URL of the JNDI provider
(optional)
|
hibernate.jndi.class
|
class of the JNDI InitialContextFactory
(optional)
|
hibernate.connection.username
|
database user
(optional)
|
hibernate.connection.password
|
database user password
(optional)
|
Table 3.2. Hibernate Datasource Properties
Here's an example hibernate.properties file for an application server provided JNDI datasource:
hibernate.connection.datasource = java:/comp/env/jdbc/test
hibernate.transaction.factory_class = \
org.hibernate.transaction.JTATransactionFactory
hibernate.transaction.manager_lookup_class = \
org.hibernate.transaction.JBossTransactionManagerLookup
hibernate.dialect = org.hibernate.dialect.PostgreSQLDialect
JDBC connections obtained from a JNDI datasource will automatically participate in the container-managed transactions of the application server.
Arbitrary connection properties may be given by prepending "hibernate.connnection" to the property name. For example, you may specify a charSet using hibernate.connection.charSet.
You may define your own plugin strategy for obtaining JDBC connections by implementing the interface org.hibernate.connection.ConnectionProvider. You may select a custom implementation by setting hibernate.connection.provider_class.
