Advantages
The advantage of using data access objects is the relatively simple and rigorous separation between two important parts of an application that can and should know almost nothing of each other, and which can be expected to evolve frequently and independently. Changing business logic can rely on the same DAO interface, while changes to persistence logic do not affect DAO clients as long as the interface remains correctly implemented.
- can be used in a large percentage of applications - anywhere data storage is required.
- hide all details of data storage from the rest of the application.
- act as an intermediary between the application and the database. They move data back and forth between objects and database records.
- allow ripple effects from possible changes to the persistence mechanism to be confined to a specific area.
In the specific context of the Java programming language, Data Access Objects as a design concept can be implemented in a number of ways. This can range from a fairly simple interface that separates the data access parts from the application logic, to frameworks and commercial products. DAO coding paradigms can require some skill. Use of technologies like Java persistence technologies and JDO ensures to some extent that the design pattern is implemented. Technologies like Enterprise JavaBeans come built into application servers and can be used in applications that use a JEE application server. Commercial products like TopLink are available based on Object-relational mapping (ORM). Popular open source ORM products include Doctrine, Hibernate, iBATIS and Apache OpenJPA.
The expected benefit of use of Data Access Objects in a Java scenario is:
- Improved efficiency and performance of the data layer since it is standard reusable software.
- Modifications can be made to the DAO implementation without altering other decoupled modules of the application.
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