This article is about the Data Access Object design pattern in object-oriented software design, not about the Data Access Objects library from Microsoft. Data Access Objects (DAO) were an object oriented interface created by Microsoft which allowed early versions of Microsoft Access and Visual Basic the Jet database engine. ...

Description

In computer software, a Data Access Object (DAO) is an Object (computer science) that provides an abstract interface to some type of database or persistence mechanism, providing some specific operations without exposing details of the database. This isolation separates the concerns of what data accesses the application needs, in terms of domain-specific objects and data types (the public interface of the DAO), and how these needs can be satisfied with a specific DBMS, database schema, etc. (the implementation of the DAO). It has been suggested that this article or section be merged with Computer program. ... In strictly mathematical branches of computer science the term object is used in a purely mathematical sense to refer to any thing. While this interpretation is useful in the discussion of abstract theory, it is not concrete enough to serve as a primitive datatype in the discussion of more concrete... An interface defines the communication boundary between two entities, such as a piece of software, a hardware device, or a user. ... This article is about computing. ...

This design pattern is equally applicable to most programming languages, most types of software with persistence needs and most types of database, but it is traditionally associated with J2EE 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. Java 2 Platform, Enterprise Edition or Java EE (formerly also J2EE) is a programming platform – part of the Java platform – for developing and running distributed multi-tier architecture applications, based largely on modular components running on an application server. ... Java 2 Platform, Enterprise Edition or Java EE (formerly also J2EE) is a programming platform – part of the Java platform – for developing and running distributed multi-tier architecture applications, based largely on modular components running on an application server. ...

Advantages

The advantage of using data access objects is the relatively simple and rigorous separation between two important parts of an application which 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.

In the specific context of the Java, Data Access Objects can be used to insulate an application from the particularly numerous, complex and varied Java persistence technologies, which could be JDBC, JDO, EJB CMP, TopLink, Hibernate, iBATIS, or many others. Using Data Access Objects means the underlying technology can be upgraded or swapped without changing other parts of the application. “Java language” redirects here. ... The Java Persistence API, sometimes referred to as JPA, is a Java programming language framework that allows developers to manage relational data in Java Platform, Standard Edition and Java Platform, Enterprise Edition applications. ... JDBC is an API for the Java programming language that defines how a client may access a database. ... Java Data Objects, or JDO, is a specification of Java object persistence. ... Simple EJB Architecture Enterprise Java Beans (EJB) is a managed, server-sided component for modular construction of enterprise applications. ... TopLink is an object-relational mapping package for Java developers. ... Hibernate is an object-relational mapping (ORM) solution for the Java language: it provides an easy to use framework for mapping an object-oriented domain model to a traditional relational database. ... iBATIS is a persistence framework which enables mapping sql queries to POJOs (Plain Old Java Objects). ...

See also

• Data Transfer Object
• Design Patterns
• Object-relational mapping
• Service Data Object

Data Transfer Objects (DTO), a. ... This article is about the book by Gamma et al. ... Object-Relational mapping (aka O/RM, ORM, and O/R mapping) is a programming technique for converting data between incompatible type systems in databases and object-oriented programming languages. ... Service Data Objects is a technology that allows heterogeneous data to be accessed in a uniform way. ...

External links

• Core J2EE Patterns - Data Access Object
• Data Access Objects versus Object Relational Mapping

Tools

• DAO-Generator DAO and DTO code generator for most of the popular RDBMS
• DB Solo JDBC/EJB 3.0 DAO code generator
• MDAOG DAO code generator for PostgreSQL databases
• CodeFutures (Firestorm/DAO) DAO + DTO + Web Tier code generator for JDBC, EJB 2.0, JPA, Hibernate

PostgreSQL is a free software object-relational database management system (ORDBMS), released under a BSD-style license. ...

References

1. ^ Core J2EE Patterns - Data Access Objects. Sun Microsystems Inc. (2007-08-02).