As a persistence service, Hibernate must work with multiple databases and within various application environments. Supporting these variations requires Hibernate to be highly configurable to adapt to different environments. After all, running a standalone application can be quite different from running a web application. Differences in obtaining database connections, for instance, can be significant. Hibernate is typically configured in two steps.
First, you configure the Hibernate service. This includes database connection parameters, caching, and the collection of persistent classes man–aged by Hibernate. Second, you must provide Hibernate with information about the classes to be persisted. Persistent class configuration allows you to bridge gaps between the class and databases.
Although it's commonly used within J2EE application servers, such as WebSphere and JBoss, Hibernate can also be used in standalone applications. Requirements vary for different environments, and Hibernate can be configured to adapt to them. Hibernate works with various support services, such as connection pools, caching services, and transaction managers. It also lets you maintain additional support services by implementing simple interfaces.
Individual persistent classes are also highly configurable. Each class may have a different method to generate identifier values, and it's possible to persist complex object hierarchies. You can also customize specific object properties mapping to a SQL type, depending on the data types available in the database. There is much more to configuring persistent classes, as we'll discuss in next article.
