Business Objects represent the data client. They are the objects that need access to the datasource to obtain and store data. Data Access Objects abstract the relying data access implementation for the business objects to enable transparent access to the datasource. The business objects also handle data store and load operations to the Data Access Objects. A DataSource shows a database such as a XML repository, relational database, flat file, mainframe system etc. Data Domain Objects or Transfer Objects transfer data between data access objects and client.

A typical DAO defined has the following components:

• A Spring framework or DAO factory class to inject a DAO class.
• A DAO interface
• A concrete class that represents the DAO interface. Your concrete class will make use of open source or JDBC API framework API like IBatis, Hibernate etc.
• Data transfer objects transfer data between data access objects and business objects or Domain Objects if you are using any Object-to-Relational Mapping tools like Hibernate.