Chapter 3. Configuration

Because Hibernate is designed to operate in many different environments, there are a large number of configuration parameters. Fortunately, most have sensible default values and Hibernate is distributed with an example hibernate.properties file in etc/ that shows the various options. Just put the example file in your classpath and customize it.

3.1. Programmatic configuration

An instance of org.hibernate.cfg.Configuration represents an entire set of mappings of an application's Java types to an SQL database. The Configuration is used to build an (immutable) SessionFactory. The mappings are compiled from various XML mapping files.
You may obtain a Configuration instance by instantiating it directly and specifying XML mapping documents. If the mapping files are in the classpath, use addResource():
Configuration cfg = new Configuration()
    .addResource("Item.hbm.xml")
    .addResource("Bid.hbm.xml");
An alternative (sometimes better) way is to specify the mapped class, and let Hibernate find the mapping document for you:
Configuration cfg = new Configuration()
    .addClass(org.hibernate.auction.Item.class)
    .addClass(org.hibernate.auction.Bid.class);
Then Hibernate will look for mapping files named /org/hibernate/auction/Item.hbm.xml and /org/hibernate/auction/Bid.hbm.xml in the classpath. This approach eliminates any hardcoded filenames.
A Configuration also allows you to specify configuration properties:
Configuration cfg = new Configuration()
    .addClass(org.hibernate.auction.Item.class)
    .addClass(org.hibernate.auction.Bid.class)
    .setProperty("hibernate.dialect", "org.hibernate.dialect.MySQLInnoDBDialect")
    .setProperty("hibernate.connection.datasource", "java:comp/env/jdbc/test")
    .setProperty("hibernate.order_updates", "true");
This is not the only way to pass configuration properties to Hibernate. The various options include:
  1. Pass an instance of java.util.Properties to Configuration.setProperties().
  2. Place hibernate.properties in a root directory of the classpath.
  3. Set System properties using java -Dproperty=value.
  4. Include <property> elements in hibernate.cfg.xml (discussed later).
hibernate.properties is the easiest approach if you want to get started quickly.
The Configuration is intended as a startup-time object, to be discarded once a SessionFactory is created.