DAO stands for Data Access Object. It is a design pattern used in Java to separate the data persistence logic in a separate layer, isolating the application/business layer from the persistence layer. This way, the service remains completely unaware of how the low-level operations to access the database are done, following the principle of Separation of Logic. The DAO pattern allows data access mechanisms to change independently of the code that uses the data, making it easier to replace or modify an applications data resources.
The DAO pattern has the following components:
- Data Access Object Interface: This interface defines the standard operations to be performed on a model object(s) .
- Data Access Object Concrete Class: This class implements the above interface. This class is responsible for getting data from a data source, which can be a database, XML, or any other storage mechanism.
- Model Object or Value Object: This object is a simple POJO containing get/set methods to store data retrieved using the DAO class.
By using the DAO pattern, the data access interface is separated from the details of how it is implemented, providing the benefits of the DAO pattern. The data access mechanism can be changed easily by writing a new class that implements the same interface, and changing client code to use the new class.
Some advantages of using the DAO pattern include:
- Separation of concerns between the business logic and the persistence logic.
- Easier maintenance and modification of the code.
- Improved testability of the code.
In summary, DAO is a design pattern used in Java to separate the data persistence logic in a separate layer, isolating the application/business layer from the persistence layer. It allows data access mechanisms to change independently of the code that uses the data, making it easier to replace or modify an applications data resources.
