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Applications often need to access data from multiple data sources: relational databases, file systems, directory services, web services, and other providers. Each of these data stores has a different API to access the underlying storage mechanism, along with a whole set of idiosyncrasies.
The Data Access Object (DAO) pattern is used to hide the unique implementation quirks of these APIs. It provides a simple and common API for application developers so that the consumers of the data can be free of the complexities of the data access APIs.
The iBATIS Data Access Objects subproject is a simple implementation of the core J2EE pattern ...