2.3 Basic configuration

"Hibernate can be configured to run in almost any Java application and development environment... It’s important to understand the difference in configuring Hibernate for managed and non-managed environments..."

Tomcat is considered an unmanaged environment because it only provides "basic concurrency management via thread pooling."

"A J2EE application server such as JBoss, BEA WebLogic, or IBM WebSphere implements the standard (J2EE-specific) managed environment for Java." A managed environment provides resource pooling (like database connections), transaction and security functionality.

"Hibernate attempts to abstract the environment in which it’s deployed. In the case of a non-managed environment, Hibernate handles transactions and JDBC connections (or delegates to application code that handles these concerns). In managed environments, Hibernate integrates with container-managed transactions and datasources. Hibernate can be configured for deployment in both environments."