In computer software, a data access object (DAO) is a pattern that provides an abstract interface to some type of database or other persistence mechanism.
By mapping application calls to the persistence layer, the DAO provides some specific data operations without exposing details of the database.
It separates what data access the application needs, in terms of domain-specific objects and data types (the public interface of the DAO), from how these needs can be satisfied with a specific DBMS, database schema, etc. (the implementation of the DAO).
it is traditionally associated with Java EE applications and with relational databases (accessed via the JDBC API because of its origin in Sun Microsystems’ best practice guidelines[1] “Core J2EE Patterns” for that platform).
Use a Data Access Object (DAO) to abstract and encapsulate all access to the data source. The DAO manages the connection with the data source to obtain and store data.
The DAO pattern can be made highly flexible by adopting the Abstract Factory [GoF] and the Factory Method [GoF] patterns.
参考
Core J2EE Patterns - Data Access Object